Samacheer Kalvi Class 12 Bio Botany Solutions Chapter 7 Ecosystem

I. Choose the Most Suitable Answer From the Given Four Alternatives and Write the Option Code and the Corresponding Answer.

 

Question 1. Which of the following is not a abiotic component of the ecosystem?
(a) Bacteria
(b) Humus
(c) Organic compounds
(d) Inorganic compounds
Answer: (a) Bacteria
In simple words: Abiotic means non-living things. Bacteria are living organisms, so they are not an abiotic component of an ecosystem. They play a role as decomposers.

🎯 Exam Tip: Remember to distinguish between living (biotic) and non-living (abiotic) components in an ecosystem when answering such questions.

 

Question 2. Which of the following is / are not a natural ecosystem?
(a) Forest ecosystem
(b) Rice field
(c) Grassland ecosystem
(d) Desert ecosystem
Answer: (b) Rice field
In simple words: A rice field is made and managed by humans, not formed naturally. It is an artificial ecosystem.

🎯 Exam Tip: Natural ecosystems develop on their own without human interference, while artificial ecosystems are created or modified by humans.

 

Question 3. Pond is a type of
(a) forest ecosystem
(b) grassland ecosystem
(c) marine ecosystem
(d) fresh water ecosystem
Answer: (d) fresh water ecosystem
In simple words: Ponds contain water that is not salty, making them freshwater bodies. They are often home to a diverse range of aquatic life.

🎯 Exam Tip: Ecosystems are often classified by their water type, like freshwater, marine (saltwater), or terrestrial (land-based).

 

Question 4. Pond ecosystem is
(a) not self sufficient and self regulating
(b) partially self sufficient and self regulating
(c) self sufficient and not self regulating
(d) self sufficient and self regulating
Answer: (d) self sufficient and self regulating
In simple words: A pond ecosystem can manage itself because it has everything it needs to keep going. It balances its own processes naturally.

🎯 Exam Tip: Ecosystems tend to achieve a state of balance where they can sustain themselves without constant outside intervention.

 

Question 5. Profundal zone is predominated by heterotrophs in a pond ecosystem, because of
(a) with effective light penetration
(b) no effective light penetration
(c) complete absence of light
(d) a and b
Answer: (b) no effective light penetration
In simple words: The profundal zone is too deep for sunlight to reach properly. Because plants cannot photosynthesize there, most living things in this zone must get their food by eating other organisms or dead matter.

🎯 Exam Tip: Light is crucial for photosynthesis, so zones without light will primarily host organisms that consume rather than produce food.

 

Question 6. Solar energy used by green plants for photosynthesis is only
(a) 2-8%
(b) 2-10%
(c) 3-10%
(d) 2-9%
Answer: (b) 2 -10%
In simple words: Green plants only use a small part of the sun's energy for making their food. Most of the solar energy is not used for photosynthesis.

🎯 Exam Tip: This low efficiency highlights that a large amount of solar energy is available but not converted into chemical energy by producers.

 

Question 7. Which of the following ecosystem has the highest primary productivity?
(a) Pond ecosystem
(b) Lake ecosystem
(c) Grassland ecosystem
(d) Forest ecosystem
Answer: (d) Forest ecosystem
In simple words: Forest ecosystems have many trees and plants that produce a lot of organic matter through photosynthesis. This makes them highly productive environments.

🎯 Exam Tip: Primary productivity refers to how much organic matter is produced by producers; dense vegetation like forests generally show high productivity.

 

Question 8. Ecosystem consists of
(a) decomposers
(b) producers
(c) consumers
(d) all of the options
Answer: (d) all of the options
In simple words: An ecosystem is a complete system with living parts like producers, consumers, and decomposers, and non-living parts too. All these parts work together.

🎯 Exam Tip: A healthy ecosystem requires a balance and interaction between all its biotic components to function properly.

 

Question 9. Which one is in descending order of a food chain
(a) Producers \(\rightarrow\) Secondary consumers \(\rightarrow\) Primary consumers \(\rightarrow\) Tertiary consumers
(b) Tertiary consumers \(\rightarrow\) Primary consumers \(\rightarrow\) Secondary consumers \(\rightarrow\) Producers
(c) Tertiary consumers \(\rightarrow\) Secondary consumers \(\rightarrow\) Primary consumers \(\rightarrow\) Producers
(d) Tertiary consumers \(\rightarrow\) Producers \(\rightarrow\) Primary consumers \(\rightarrow\) Secondary consumers
Answer: (c) Tertiary consumers \(\rightarrow\) Secondary consumers \(\rightarrow\) Primary consumers \(\rightarrow\) Producers
In simple words: A food chain shows who eats whom. In a descending order, it means starting from the top eaters (tertiary consumers), then the next eaters (secondary consumers), then those who eat plants (primary consumers), and finally the plants themselves (producers).

🎯 Exam Tip: Always remember that energy flows from producers up to various levels of consumers in a food chain.

 

Question 10. Significance of food web is/are
(a) it does not maintain stability in nature
(b) it shows patterns of energy transfer
(c) it explains species interaction
(d) b and c
Answer: (d) b and c
In simple words: A food web helps us see how energy moves from one living thing to another and how different species interact by eating each other. It shows the complex connections in an ecosystem.

🎯 Exam Tip: Food webs are more complex than food chains, showing multiple feeding relationships and contributing to ecosystem stability.

 

Question 11. The following diagram represents

(a) pyramid of number in a grassland ecosystem
(b) pyramid of number in a pond ecosystem
(c) pyramid of number in a forest ecosystem
(d) pyramid of biomass in a pond ecosystem
Answer: (c) pyramid of number in a forest ecosystem
In simple words: The diagram shows a large base (T1, one tree) supporting many smaller organisms at higher levels. This inverted shape, with a broad middle, is typical for a forest's pyramid of numbers, where one large producer supports many consumers.

🎯 Exam Tip: Pyramids of numbers can be upright, inverted, or spindle-shaped depending on the ecosystem and the type of organisms at each trophic level.

 

Question 12. Which of the following is / are not the mechanism of decomposition
(a) Eluviation
(b) Catabolism
(c) Anabolism
(d) Fragmentation
Answer: (c) Anabolism
In simple words: Anabolism is about building complex molecules, which is the opposite of decomposition. Decomposition breaks down dead organic matter.

🎯 Exam Tip: Remember that anabolism is a constructive metabolic process, while catabolism and fragmentation are destructive processes involved in decomposition.

 

Question 13. Which of the following is not a sedimentary cycle
(a) Nitrogen cycle
(b) Phosphorous cycle
(c) Sulphur cycle
(d) Calcium cycle
Answer: (a) Nitrogen cycle
In simple words: The nitrogen cycle mainly takes place in the atmosphere and living organisms. Other cycles listed happen mostly in rocks and soil.

🎯 Exam Tip: Gaseous cycles (like nitrogen and carbon) have a large atmospheric reservoir, while sedimentary cycles (like phosphorus and sulfur) have their main reservoir in the Earth's crust.

 

Question 14. Which of the following are not regulating services of ecosystem services
(i) Genetic resources
(ii) Recreation and aesthetic values
(iii) Invasion resistance
(iv) Climatic regulation
(a) i and iii
(b) ii and iv
(c) i and ii
(d) i and iv
Answer: (c) i and ii
In simple words: Genetic resources and recreational values are 'provisioning' and 'cultural' services, not 'regulating' ones. Regulating services are about how ecosystems control natural processes like climate or disease.

🎯 Exam Tip: Ecosystem services are categorized into provisioning (products), regulating (benefits from natural processes), cultural (non-material benefits), and supporting (underlying processes).

 

Question 15. The productivity of the profundal zone will be low. Why?
Answer: In a pond ecosystem, the producers like phytoplankton depend on sunlight for photosynthesis. The profundal zone is the deep area of the pond where sunlight cannot reach effectively. This lack of light means that plants cannot grow there, leading to very low productivity. This dark environment means that food must come from elsewhere.
In simple words: The profundal zone in a pond gets very little sunlight. Because plants need sunlight to make food, there isn't much food produced in this deep, dark area.

🎯 Exam Tip: Always link productivity in aquatic ecosystems to light penetration, as light is a critical factor for primary producers.

 

Question 16. Discuss the gross primary productivity is more efficient than net primary productivity.
Answer:
**Gross Primary Productivity (GPP):**
This is the total amount of energy from food or biomass that plants (autotrophs) create through photosynthesis. It includes all the energy made before any is used up by the plant itself.
**Net Primary Productivity (NPP):**
NPP is the energy that remains after plants use some of their GPP for their own breathing and daily functions (respiration). So, NPP is the usable energy left over for other organisms in the ecosystem.
Therefore, GPP represents the maximum potential energy fixed, while NPP is the actual energy available. This means that GPP is always greater than NPP, as NPP = GPP - Respiration. In terms of energy fixation, GPP shows the total captured energy, making it a measure of the overall efficiency of photosynthesis, whereas NPP shows what's left for growth and consumption.
In simple words: GPP is all the food a plant makes. NPP is the food left after the plant uses some for itself. GPP is always bigger because it counts everything, even what the plant uses to stay alive.

🎯 Exam Tip: Clearly differentiate between GPP (total energy fixed) and NPP (energy remaining after respiration), using the formula NPP = GPP - Respiration.

 

Question 17. Pyramid of energy is always upright. Give reasons
Answer: An energy pyramid shows how energy moves from one feeding level (trophic level) to the next in an ecosystem. Energy is always lost as it moves up each level because organisms use energy for their own life processes, and some is lost as heat. This means that there is always less energy available at higher trophic levels compared to lower ones. Because energy decreases at each step, the pyramid of energy always stands upright, showing a wider base of energy at the producer level. This consistent decrease is due to the second law of thermodynamics, which explains that energy transfers are never 100% efficient.
In simple words: The energy pyramid always stands upright because energy is lost at each step up the food chain. Plants have the most energy, and animals that eat them get less, and so on.

🎯 Exam Tip: The upright shape of the energy pyramid is a fundamental concept due to energy loss at each trophic transfer, following the 10% law.

 

Question 18. What will happen if all producers are removed from ecosystem?
Answer: If all producers were removed from an ecosystem, several serious problems would occur:

• The entire food web would collapse because there would be no initial source of energy.
• Primary consumers (herbivores) would starve and die off as they directly feed on producers.
• After that, all other animals in the food web (secondary and tertiary consumers) would also die because their food sources would disappear.
• The number of consumers would drop sharply as producers vanish.
• Producers also help maintain the correct levels of carbon dioxide and oxygen in the air. Without them, these gas levels would become unbalanced.
• This imbalance would lead to a lack of breathable oxygen, as oxygen is a byproduct of photosynthesis.

In simple words: If all the plants disappear, everything else in the ecosystem will eventually die because there will be no food or oxygen for them. The whole system would crash.

🎯 Exam Tip: Emphasize the crucial role of producers as the base of all food chains and their essential contribution to atmospheric gas balance.

 

Question 19. Construct the food chain with the following data. Hawk, plants, frog, snake, grasshopper.
Answer: The food chain can be constructed as follows:
Plants \(\rightarrow\) Grasshopper \(\rightarrow\) Frog \(\rightarrow\) Snake \(\rightarrow\) Hawk

In this food chain:

• Plants are the producers, making their own food.
• Grasshoppers are primary consumers, eating the plants.
• Frogs are secondary consumers, eating the grasshoppers.
• Snakes are tertiary consumers, eating the frogs.
• Hawks are the top consumers, eating the snakes.

The diagram above shows a typical terrestrial food chain, illustrating how energy moves from producers to various consumers. This kind of movement of energy from producers up to top carnivores is how a food chain works.
In simple words: Plants are eaten by grasshoppers, grasshoppers are eaten by frogs, frogs are eaten by snakes, and snakes are eaten by hawks. This shows how food energy moves from one living thing to another.

🎯 Exam Tip: When constructing a food chain, always start with a producer and follow the 'eaten by' relationship to the top consumer.

 

Question 20. Name of the food chain which is generally present in all type of ecosystem. Explain and write their significance.
Answer: The detritus food chain is generally present in all types of ecosystems.

**Detritus food chain:**
This type of food chain starts with dead organic matter, which is an important energy source. A lot of organic matter comes from dead plants, animals, and their waste products. This food chain is found in every ecosystem. Energy moves from dead organic matter through organisms called detritivores (detritus consumers), then to small carnivores, and finally to large (top) carnivores. These organisms eat each other in a series, which is what we call the detritus food chain. This is a very crucial chain for recycling nutrients in the ecosystem.


**Significance:**

• Detritus, which includes dead plants, animals, and their waste, is broken down into simpler organic matter by decomposers.
• This process is essential for recycling nutrients and keeping the balance of the nutrient pool in an ecosystem.

In simple words: The detritus food chain starts with dead things. It is in every ecosystem. It is important because it breaks down dead stuff and sends nutrients back into the soil, helping new plants to grow.

🎯 Exam Tip: Emphasize that the detritus food chain is crucial for nutrient cycling and involves decomposers breaking down dead organic matter.

 

Question 21. Shape of pyramid in a particular ecosystem is always different in shape. Explain with example.
Answer: The shape of ecological pyramids can indeed vary depending on the specific ecosystem and what is being measured (number, biomass, or energy). For example, a pyramid of numbers can have different shapes.

In a forest ecosystem, the pyramid of number is often spindle-shaped. The base of the pyramid (T1) has large trees (producers), which are fewer in number. The next level (T2), herbivores like fruit-eating birds, elephants, and deer, are more numerous. The secondary consumers (T3) are fewer again, and the tertiary consumers (T4) like lions, foxes, and snakes are even lesser in number. This leads to a pyramid that is wide in the middle and narrow at the top and bottom. This contrasts with a grassland, where many small plants support fewer herbivores, creating an upright pyramid.
In simple words: Pyramids that show how many living things are at each level can look different. In a forest, there are few big trees but many small animals that eat them, making the pyramid wider in the middle.

🎯 Exam Tip: Pay attention to the specific type of pyramid (number, biomass, or energy) and the ecosystem (forest, grassland, pond) as these factors determine its shape.

 

Question 22. Generally human activities are against to the ecosystem, whereas you a student how will you help to protect the ecosystem?
Answer: As a student, I can help protect the ecosystem by practicing these habits in my daily life:

• Buy and use only eco-friendly products and always recycle them.
• Plant and grow more trees to improve air quality and provide habitats.
• Choose sustainably farmed products like vegetables, fruits, and greens to reduce the use of natural resources.
• Recycle waste and reduce the amount of garbage I produce.
• Save water and electricity by using less.
• Avoid or stop using household chemicals and pesticides that harm nature.
• Make sure my family's cars and vehicles are well-maintained to reduce air pollution (carbon emissions).
• Help spread awareness and educate my friends and family about why it is important to protect ecosystems. We can all work together to find ways to reduce these problems.

In simple words: To protect nature, I will use eco-friendly things, plant trees, save water and electricity, recycle, and teach others to do the same.

🎯 Exam Tip: Focus on actionable and practical steps that can be taken at an individual level to promote environmental sustainability.

 

Question 23. Generally in summer the forest are affected by natural fire. Over a period of time it recovers itself by the process of successions. Find out the types of succession and explain.
Answer: When a forest is affected by a natural fire, it recovers over time through different types of ecological succession. Here are the types of succession:

**Secondary Succession:**
This type of succession happens in an area where a community of plants already existed but was destroyed by a disturbance like a fire, flood, or human activity. It is called secondary succession because life was there before, and now it is coming back. Secondary succession usually takes less time to complete compared to primary succession because soil is already present. The image shows the stages of recovery, from pioneer species to a climax community.


Here's a table showing the difference between primary and secondary succession:

Generally, secondary succession takes less time than primary succession. For example, a forest destroyed by fire can be re-occupied by herbs over a period of time.

**3. Autogenic succession:**
This type of succession happens because of living factors (biotic factors). The plants in an area change their environment, which then causes new types of plants to replace them. This is a natural process driven by the organisms themselves. For instance, in a forest, large trees create shade, which helps shade-loving plants grow while others that need more light disappear.

**4. Allogenic succession:**
This type of succession happens because of non-living factors (abiotic factors). Changes in the environment, like soil erosion or changes in nutrient levels, cause new communities to replace existing ones. This is not caused by the living organisms themselves but by outside forces. For example, soil erosion in a forest can change the soil's nutrients, leading to different plants growing there.

**5. Autotrophic succession:**
This happens when green plants (autotrophs) are the main type of life in the early stages of succession, especially in places rich in inorganic substances. As green plants take over, the amount of organic matter slowly increases, and the flow of energy in the ecosystem also goes up.

**6. Heterotrophic succession:**
This happens when organisms like bacteria, fungi, actinomycetes, and animals (heterotrophs) are the main type of life in the early stages of succession. This succession usually happens in places with a lot of organic matter, and over time, the energy content in the ecosystem gradually decreases because heterotrophs consume rather than produce energy.
In simple words: Forests regrow after fire through different types of succession. Secondary succession is when an area recovers after a disturbance, and it's faster because soil is already there. Autogenic succession is driven by living things, and allogenic is driven by non-living things like soil changes.

🎯 Exam Tip: Be able to define and provide examples for each type of succession, highlighting the key differences in their causes and progression.

Question 24. Draw a pyramid from following details and explain in brief. Quantities of organisms are given – Hawks – 50, plants – 1000. rabbit and mouse - 250 +250, pythons and lizard- 100 + 50 respectively.
Answer: This pyramid shows the amount of living material, or biomass, at each level in an ecosystem. In this example, it represents the number of organisms at each level.

• A pyramid of biomass is a visual way to show the total amount of living matter at each feeding level in an ecosystem.
• In grassland and forest ecosystems, the pyramid is usually upright. This means there is more biomass at the bottom (producers) and less at the top (top carnivores).
• For this specific data, the pyramid will be upright, showing a clear decrease in numbers as we go up the food chain.

In simple words: We draw a pyramid where the biggest group (plants) is at the bottom, and the smallest group (hawks) is at the top. This type of pyramid shows how much life is at each level of the food chain, usually getting smaller as you go up.

🎯 Exam Tip: When drawing ecological pyramids, always ensure the base represents producers and the subsequent layers represent different consumer levels. Clearly label each trophic level and the number or biomass it represents.

 

Question 25. Various stages of succession are given below. From that rearrange them accordingly. Find out the type of succession and explain in detail.
Reed-swamp stage, phytoplankton stage, shrub stage, submerged plant stage, forest stage, submerged free-floating stage, marsh meadow stage.
Answer: The succession described here is called hydrosere, which is plant succession that starts in a water environment. The stages should be rearranged in the correct order to show how an area changes from open water to a forest over time.
The correct order of stages for a hydrosere is:
1. Phytoplankton stage
2. Submerged plant stage
3. Submerged free-floating stage
4. Reed-swamp stage
5. Marsh meadow stage
6. Shrub stage
7. Forest stage
Here is a detailed explanation of each stage:
(1) Phytoplankton Stage: This is the very first stage of succession in a water body. Tiny floating plants (phytoplankton) like blue-green algae, diatoms, and bacteria are the first to grow. When these organisms die, they add organic matter and nutrients to the pond. This makes the pond richer and helps the next stages of plants to grow.
(2) Submerged Plant Stage: After the phytoplankton, rooted plants that live completely underwater start to grow. As plankton die and break down, silt (fine soil) from rain also collects at the bottom of the pond. This forms a loose mud, which allows plants like Vallisneria and Hydrilla to take root. The decaying parts of these plants continue to make the pond shallower.
(3) Submerged Free-Floating Stage: In this stage, the pond becomes shallower, around 2-5 feet deep. Rooted plants with large leaves that float on the surface, like Nelumbo (lotus) and Nymphaea (water lily), begin to grow. Some free-floating plants like Azolla and Pistia are also present. The death and decay of these plants make the pond even shallower.
(4) Reed-Swamp Stage: This is also known as the amphibious stage because plants can grow in both water and on land. Rooted floating plants are replaced by taller plants like Typha and Phragmites, which can live in partially submerged conditions. As this stage progresses, the water level reduces significantly, making it unsuitable for fully aquatic plants.
(5) Marsh Meadow Stage: When the water level keeps dropping, the pond becomes a marshy area. Plants from the Cyperaceae and Poaceae families (like sedges and grasses) grow here. They form a thick mat of vegetation with strong root systems that absorb a lot of water. The soil becomes dry, and the marshy plants slowly disappear, preparing the ground for shrubs.
(6) Shrub Stage: At this point, the marshy land becomes dry enough for terrestrial plants like shrubs (e.g., Salix, Cornus) and small trees (e.g., Populus, Alnus) to invade. These plants absorb a large amount of water, making the area even drier. Humus (rich organic matter) builds up in the soil, creating good conditions for microorganisms and paving the way for new tree species.
(7) Forest Stage: This is the final and most stable community of a hydrosere, also called the climax community. Many different types of trees grow here, forming various kinds of forests such as temperate mixed forests or tropical rainforests. This stage shows the complete transformation from a water body to a mature forest ecosystem.
In simple words: This is about how a pond slowly turns into a forest. It starts with tiny plants in the water, then bigger underwater plants, then plants that float on top. After that, marsh plants grow, followed by bushes, and finally, tall trees form a forest. Each step adds more soil and changes the environment.

🎯 Exam Tip: Remember the sequence of stages in hydrosere and how each stage prepares the environment for the next. Focus on the key plant types and environmental changes in each step.

12th Bio Botany Guide Ecosystem Additional Important Questions and Answers

I. Choose the correct answer

 

Question 1. The most stable and productive ecosystem seen on the earth is _____.
(a) Mangrove ecosystem
(b) Grassland ecosystem
(c) Pond ecosystem
(d) Forest ecosystem
Answer: (d) Forest ecosystem
In simple words: Forest ecosystems are the most steady and produce the most new plant and animal life on Earth. They have a rich variety of plants and animals that work together in a balanced way.

🎯 Exam Tip: Understand that stability in an ecosystem often comes from high biodiversity and complex interactions, which are characteristic of mature forest ecosystems.

 

Question 2. In an ecosystem, the energy flow is always _____.
(a) Unidirectional
(b) Top to bottom
(c) Chain form
(d) Multi directional
Answer: (a) Unidirectional
In simple words: Energy in an ecosystem always moves in one direction. It starts from the sun, goes to plants, then to plant-eaters, and finally to meat-eaters, without going backward.

🎯 Exam Tip: Remember the fundamental principle of energy flow in ecology: it's always from lower trophic levels to higher ones, and cannot be recycled in the same way as matter.

 

Question 3. Grass → Goat → Man. This is the grazing food chain, choose the correct option.
(a) Goat is primary producer, secondary trophic level and herbivore
(b) Grass is a primary producer, herbivore, and first trophic level.
(c) Goat is a primary consumer, herbivore, second trophic level
(d) Goat is a primary consumer, herbivore, first trophil level
Answer: (c) Goat is a primary consumer, herbivore, second trophic level
In simple words: In this food chain, grass makes its own food (producer). The goat eats the grass, so it's the first eater (primary consumer) and eats only plants (herbivore), placing it at the second feeding level.

🎯 Exam Tip: Clearly identify producers (make food), primary consumers (eat producers), secondary consumers (eat primary consumers), and their corresponding trophic levels (1st, 2nd, 3rd, etc.).

 

Question 4. Choose the incorrect statement from following
(a) Pyramid of energy is always upright
(b) In grass land and forest ecosystem pyramid of biomass as upright.
(c) Pyramid of number shows three different shape of pyramids like upright, spindle and inverted
(d) Food web is used for the construction of ecological pyramid.
Answer: (d) Food web is used for the construction of ecological pyramid.
In simple words: Ecological pyramids are built using individual food chains, not the entire food web. A food web shows many food chains linked together, which is too complex for a simple pyramid.

🎯 Exam Tip: Understand the distinct roles of food chains, food webs, and ecological pyramids. Pyramids simplify the flow of energy or biomass from specific food chains, not the entire web.

 

Question 5. Assertion : If the decomposers were removed completely from the ecosystem the functioning of ecosystem will be adversely affected. Reason: The cycling of nutrients between abiotic and biotic components will be blocked.
(a) A and R are correct
(b) A and R are not correct
(c) A is correct R is wrong
(d) R is not a correct explanation for A
Answer: (a) A and R are correct
In simple words: Both statements are true. If there are no decomposers, dead plants and animals won't break down, so nutrients can't return to the soil for new plants to grow. This would stop the whole ecosystem from working properly.

🎯 Exam Tip: Always remember that decomposers are essential for nutrient cycling, linking the living (biotic) and non-living (abiotic) parts of an ecosystem.

 

Question 6. Assertion : An ecological pyramid is a diagrammatic (or) graphic representation of the trophic structure and function. Reason: Various trophic levels of a food chain are considered in ecological pyramid.
(a) Both are not correct
(b) R is not related to A
(c) Both A and R are wrong
(d) R is the correct explanation of A
Answer: (d) R is the correct explanation of A
In simple words: The reason statement explains why the assertion is true. Ecological pyramids show the feeding levels (trophic structure) and how energy or biomass moves (function), and they do this by looking at each feeding level in a food chain.

🎯 Exam Tip: For assertion-reason questions, first determine if each statement is true, then check if the reason correctly explains the assertion. Look for a causal link between them.

 

Question 7. Match the following
Read this statement and fill it with correct (A) and (B)
Carbon stored in fossil fuel is ......(A)........... and carbon stored in the biosphere is ..........(B)............

(a) Brown carbon – Black carbon
(b) Grey carbon – Green carbon
(c) Black carbon – Brown carbon
(d) Green carbon – Blue carbon
Answer: (b) Grey carbon – Green carbon
In simple words: Carbon hidden in fossil fuels like coal is called grey carbon. Carbon found in living things and plants on Earth, like in forests, is called green carbon.

🎯 Exam Tip: Familiarize yourself with the different classifications of carbon (green, grey, blue, brown, black) and where each type is stored in the environment.

 

Question 8. Match the following and find the correct answer

(a) (i) – B; (ii) – C; (iii) – D; (iv) – A
(b) (i) – C; (ii) – D; (iii) – B; (iv) – A
(c) (i) – B; (ii) – A; (iii) – D; (iv) – C
(d) (i) – D; (ii) – C; (iii) – B; (iv) – A
Answer: (d) (i) – D; (ii) – C; (iii) – B; (iv) – A
In simple words: Green carbon is in the biosphere. Grey carbon is in fossil fuels. Blue carbon is in the atmosphere. Brown carbon is found in man-made forests and wood products.

🎯 Exam Tip: Matching questions often test specific definitions. Make sure to clearly associate each carbon type with its primary location or source (e.g., green-biosphere, grey-fossil fuels, blue-atmosphere, brown-industrial forests).

 

Question 9. Choose the incorrect pair

Answer: (d) Fragmentation – Release of inorganic nutrients from the humus.
In simple words: Fragmentation is when decomposers break down large pieces of dead organic matter into smaller ones. It's not about releasing simple nutrients from humus, that's mineralization.

🎯 Exam Tip: Differentiate clearly between the stages of decomposition: fragmentation (physical breakdown), catabolism (chemical breakdown), leaching (nutrient movement), humification (humus formation), and mineralization (release of inorganic nutrients).

 

Question 10. Choose the correct pair

(a) B and C
(b) A and C
(c) B, C and D
(d) A, B and D
Answer: (d) A, B and D
In simple words: This question checks how long different types of plants take to grow in an ecosystem, which is important for understanding ecological succession. Grasses and shrubs usually take a long time (5-150 years), while grasses and perennials are quicker (3-4 years). Shrubs and trees take the longest, over 150 years.

🎯 Exam Tip: Pay attention to the typical timeframes for different plant communities in ecological succession, as these are often tested in questions about ecosystem development.

 

Question 11. The plants which colonize first in a barren area is called _____.
(a) Pioneers
(b) Serai
(c) Autogenic
(d) Allogenic
Answer: (a) Pioneers
In simple words: The first plants to grow in a new, empty area are called pioneer species. They are like the first explorers, preparing the ground for other plants to follow.

🎯 Exam Tip: Remember that pioneer species are crucial for primary succession, as they initiate soil formation and create conditions for subsequent communities.

 

Question 12. The term 'ecosystem' was proposed by..................in the year 1935.
(a) A.G. Hoxley
(b) A.G.Tansley
(c) Odum
(d) Lindeman
Answer: (b) A.G. Tansley
In simple words: A.G. Tansley was the scientist who first used the word "ecosystem" in 1935 to describe how living things and their environment work together.

🎯 Exam Tip: Keep note of key scientists and their contributions to ecological concepts, such as A.G. Tansley for the term 'ecosystem'.

 

Question 13. The position of organisms in food chain is refers to _____.
(a) Ecosystem
(b) Trophic level
(c) Food chain
(d) Ten percent law
Answer: (b) Trophic level
In simple words: The "trophic level" is just a fancy way of saying where an organism fits in the food chain, like if it's a plant, a plant-eater, or a meat-eater.

🎯 Exam Tip: Understand that each step in a food chain represents a trophic level, indicating the organism's feeding position and energy source.

 

Question 14. Temperate mixed forest, tropical rain forest tropical deciduous forest are _____.
(a) Climax communities
(b) T ertiary communities
(c) Primary communities
(d) Secondary communities
Answer: (a) Climax communities
In simple words: These types of forests are like the final, most stable forms an ecosystem can take. They are fully developed and can stay the same for a very long time unless something big changes them.

🎯 Exam Tip: Climax communities represent the stable, mature stage of ecological succession, characterized by high biodiversity and complex interactions adapted to the regional climate.

 

Question 15. Assertion and Reason
Assertion : Photosynthetically active radiation (PAR) which is between the range of 400 – 700 nm wave length. Reason : At night PAR is zero and during midday in the summer, PAR often reaches 2000 – 3000 millimoles/square meter/second.
(a) R does not explains A
(b) R explaining A
(c) A is correct R is wrong
(d) Both A and R are wrong
Answer: (a) R does not explains A
In simple words: The assertion correctly states the wavelength range of PAR. The reason gives facts about PAR levels at night and midday but doesn't explain *why* PAR has that specific wavelength range.

🎯 Exam Tip: When evaluating assertion-reason questions, confirm both statements are individually true, then check if the reason provides a direct explanation for the assertion, not just related facts.

 

Question 17. Choose the correct statement
(a) Only 2 – 10% of solar energy is used by green plants for photo synthesis
(b) Only 56% of the solar energy is used by green plants for photosynthesis.
(c) Productivity can be expressed in terms of kcal / m2 / 10 year
(d) Limnology is the study about ocean.
Answer: (a) Only 2 – 10% of solar energy is used by green plants for photo synthesis
In simple words: Green plants capture only a small part, about 2 to 10%, of the sun's energy for making their food through photosynthesis. Most of the sun's energy is not used by plants.

🎯 Exam Tip: Remember the "ten percent law" in ecology, which roughly states that only about 10% of energy is transferred from one trophic level to the next, starting with producers using a small fraction of solar energy.

 

Question 18. Blue carbon ecosystems is related to ...................
(a) Carbon sequestration
(b) Productivity
(c) Visibility
(d) Phosphorus cycle
Answer: (a) Carbon sequestration
In simple words: Blue carbon ecosystems, like mangrove forests and seagrass beds, are special because they are very good at capturing and storing carbon dioxide from the air and ocean. This helps fight climate change.

🎯 Exam Tip: Associate "blue carbon" with marine and coastal ecosystems that excel at carbon sequestration, such as mangroves, salt marshes, and seagrass meadows.

 

Question 19. Choose the correct pair related to this statement
Secondary productivity can be defined as
(a) Amount of energy in the tissues of consumer (or) heterotrophs
(b) Amount of biomas formation
(c) Rate of energy formation
(d) Rate of energy utilization
Answer: (a) Amount of energy in the tissues of consumer (or) heterotrophs
In simple words: Secondary productivity is how much new living material (biomass) is made by consumers, who eat other living things, in an ecosystem. It shows how much energy they have stored.

🎯 Exam Tip: Primary productivity refers to producers, while secondary productivity refers to consumers (heterotrophs), representing the energy stored at their trophic levels.

 

Question 20. Which one of the following will be the shape of the pyramid. If you consider the following statement.
"No. of fruit eating birds, elephant, deer depends on large sized tree (producer) which are lesser in number and lesser number of secondary consumer (fox and snake) and final trophic level tertiary consumer lion.
(a)
(b)
(c)
(d)
Answer: (d) [Spindle-shaped pyramid]
In simple words: The pyramid will be spindle-shaped. This means it has a narrow base (one large tree), widens for the many plant-eaters (birds, deer), then narrows again for the fewer meat-eaters (fox, snake), and becomes very narrow at the top for the single top predator (lion).

🎯 Exam Tip: Understand that in a forest, the pyramid of numbers can be spindle-shaped because a single large producer (tree) supports many primary consumers, which are then eaten by fewer secondary and tertiary consumers.

 

Question 21. Choose the odd one out
(a) Flagship species
(b) Rehabilitation
(c) Maintaining biodiversity
(d) Anthropogenic activities
Answer: (d) Anthropogenic activities
In simple words: "Anthropogenic activities" means human actions, which often harm the environment. The other options (flagship species, rehabilitation, maintaining biodiversity) are all about protecting or fixing ecosystems.

🎯 Exam Tip: Identify the common theme among most options (conservation) and the one that goes against it (human-caused impact) to find the odd one out.

 

Question 22. Ecological succession refers to ....................
(a) Gradual, fairly changes and pH development of a given area
(b) Linking of ecosystem
(c) Energy transfer
(d) Biotic communities
Answer: (a) Gradual, fairly changes and pH development of a given area
In simple words: Ecological succession is when an area slowly changes over time, with different groups of plants and animals replacing each other. This includes changes in the soil and water acidity.

🎯 Exam Tip: Ecological succession is fundamentally about predictable changes in species composition and environmental conditions over time in an ecosystem.

 

Question 23. Succession occur in which area ?
Answer: Succession occurs in areas affected by natural events like floods, earthquakes, and also in areas disturbed by human activities (anthropogenic areas). This means succession can happen in both natural and human-altered environments where new plant and animal communities develop.
In simple words: Succession happens in places changed by natural disasters like floods or earthquakes, and also where people have caused changes.

🎯 Exam Tip: Remember that succession isn't just a natural process; human activities also create opportunities for ecological succession to occur.

 

Question 24. Plant succession in saline water is.......................
Answer: Plant succession in saline (salty) water is called halosere. It describes how plant communities change and replace each other in very salty environments like coastal marshes or salt flats. Over time, the environment becomes less salty as plants grow and die.
In simple words: When plants grow and change over time in salty water, it's called halosere.

🎯 Exam Tip: Distinguish between different types of seral successions based on the initial habitat: hydrosere (water), xerosere (dry), psammosere (sand), and halosere (saline).

 

Question 25. The replacement of existing community by other factors like soil erosion, leaching etc. is .......................
Answer: The replacement of an existing community due to outside factors like soil erosion or nutrients being washed away (leaching) is called allogenic succession. In this type, the environment changes because of non-living factors, not because of the living organisms themselves.
In simple words: When outside things like soil washing away make new plants grow in an area, it's called allogenic succession.

🎯 Exam Tip: Differentiate between autogenic succession (driven by biotic factors) and allogenic succession (driven by abiotic factors like erosion or volcanic eruptions).

 

Question 26. The type of succession takes less time to the time taken for primary succession ?
Answer: The type of succession that takes less time compared to primary succession is secondary succession. Secondary succession happens in an area where life once existed but was disturbed (like after a forest fire or flood), so some soil and seeds are already present, making the recovery faster.
In simple words: Secondary succession is faster because it happens where living things used to be, so it doesn't have to start from scratch like primary succession.

🎯 Exam Tip: Remember that secondary succession is typically faster than primary succession because it starts in an area where soil is already present and some life forms may have survived.

 

Question 27. The type of succession in which organisms like bacteria, fungi, actinomycetes and animals are dominant during its early stages is ....................
(a) Heterotrophic
(b) Allogenic
(c) Autotrophic
(d) Autogenic
Answer: (a) Heterotrophic
In simple words: When succession starts with many organisms that get food from others (like bacteria, fungi, and animals), it's called heterotrophic succession. They rely on existing organic matter.

🎯 Exam Tip: Understand that autotrophic succession is dominated by producers (like plants) in early stages, while heterotrophic succession is dominated by consumers/decomposers.

 

Question 28. Match the following:

(a) A – iv), B – iii), C – ii), D – i)
(b) A – i), B – ii), C – iii), D – iv)
(c) A – ii), B – iii), C – iv), D – i)
(d) A – iii), B – ii), C – i), D – iv)
Answer: (a) A – iv), B – iii), C – ii), D – i)
In simple words: Allogenic succession is caused by non-living (abiotic) factors. Autotrophic succession starts in places with many non-living nutrients. Autogenic succession is driven by living (biotic) factors. Secondary succession happens in areas that were once disturbed, like bare rock.

🎯 Exam Tip: Accurately matching terms to their definitions is key. Allogenic involves external (abiotic) factors, autogenic involves internal (biotic) factors, autotrophic relates to producers, and secondary succession starts on disturbed land.

 

Question 29. Pioneer community like blue green algae, green algae, diatoms, bacteria etc are present in stage of hydrosere.
Answer: The pioneer community, including blue-green algae, green algae, diatoms, and bacteria, are present in the **phytoplankton stage** of hydrosere. This early stage is crucial for building up organic matter in a water body.
In simple words: The very first living things like tiny algae and bacteria in a watery area are found in the phytoplankton stage of water succession.

🎯 Exam Tip: Remember that pioneer species are the first organisms to colonize a new or disturbed habitat, initiating ecological succession.

 

Question 30. Rooted floating plants like Nelumbo Nymphaea and Trapa and free floating SPS wolffia and lemna are present in this stage is
Answer: Rooted floating plants like Nelumbo, Nymphaea, and Trapa, along with free-floating plants like Wolffia and Lemna, are characteristic of the **submerged free floating stage**. These plants thrive where water is still deep enough for their roots to not reach the bottom, but the leaves can float.
In simple words: Water lilies and other plants that float on the water, even if their roots are in the mud below, are found in the submerged free-floating stage.

🎯 Exam Tip: Focus on the growth habits of plants-whether they are fully submerged, rooted and floating, or free-floating-to identify the correct succession stage.

 

Question 31. Submerged hydrophytes like char a, utricularia, vallisneria, hydrilla are present in the stage of hydrosere.
Answer: Submerged hydrophytes such as Chara, Utricularia, Vallisneria, and Hydrilla are present in the **submerged plant stage** of hydrosere. These plants live completely under the water.
In simple words: Plants that live entirely underwater, like Hydrilla, are found in the submerged plant stage.

🎯 Exam Tip: Hydrophytes are plants adapted to live in aquatic environments, and understanding their specific growth forms helps in identifying succession stages.

 

Question 32. Mat - like vegetation with the help of much branched root system is the character of stage of hydrosere
Answer: Mat-like vegetation, supported by a much-branched root system, is a characteristic feature of the **marsh meadow stage** of hydrosere. This dense growth helps to stabilize the soil and gradually dry out the area.
In simple words: When plants grow very close together with many roots, forming a thick mat that starts to dry out wet areas, it's called the marsh meadow stage.

🎯 Exam Tip: The development of a dense, mat-like root system signifies the transition from aquatic to more terrestrial conditions in hydrosere.

 

Question 33. Species of cyperaceae and poaceae like carex, juncus cyperus and eleocharis colonise in this i area is
Answer: Species from the Cyperaceae and Poaceae families, such as Carex, Juncus, Cyperus, and Eleocharis, colonize the **marsh meadow stage**. These plants are well-adapted to damp soil conditions.
In simple words: Certain types of grasses and sedges grow in the marsh meadow stage, helping the area become drier.

🎯 Exam Tip: Recognize specific plant families like Cyperaceae (sedges) and Poaceae (grasses) as indicators of specific stages in ecological succession, especially in wet environments.

 

Question 34. Salix and cornus (shrubs) and trees like populous and alnus are present in the stage.
Answer: Salix and Cornus (shrubs), along with trees like Populus and Alnus, are present in the **shrub stage**. This stage marks a significant shift towards more woody, terrestrial vegetation.
In simple words: Shrubs like Salix and young trees start growing in the shrub stage, making the area less wet.

🎯 Exam Tip: The appearance of woody shrubs and small trees signals a progression from herbaceous plants towards a forest community in succession.

 

Question 35. Say true or false Reduce, reuse, recycle are "three R” s for waste management.
Answer: True
In simple words: The statement is correct; 'reduce, reuse, recycle' are indeed the three main rules for handling waste.

🎯 Exam Tip: Always confirm the core concepts related to environmental management as they are frequently tested.

 

Question 36. is the best example for urban eco restoration in the state of Tamilnadu.
Answer: The **urban ecosystem restoration model** is the best example for urban eco restoration in the state of Tamilnadu. This model focuses on bringing natural elements back into city environments.
In simple words: In Tamilnadu, the best way to restore nature in cities is by using the urban ecosystem restoration model.

🎯 Exam Tip: When answering about specific examples, ensure you name the specific model or initiative mentioned in the context.

 

Question 37. Initiation of plant succession on barren rock is
Answer: The initiation of plant succession on barren rock is called **lithosere**. This type of succession starts on completely new or exposed rock surfaces.
In simple words: When plants start growing on bare rocks for the first time, it is known as lithosere.

🎯 Exam Tip: Differentiate between different types of primary succession based on the initial substrate-hydrosere (water), psammosere (sand), and lithosere (rock).

 

Question 38. Succession with minimal amount of water is
(a) Merosere
(b) Psammosere
(c) Halosere
(d) Xerosere
Answer: (d) Xerosere
In simple words: Succession that happens in very dry places with little water is called xerosere.

🎯 Exam Tip: Xerosere refers to succession in dry conditions, contrasting with hydrosere which occurs in aquatic environments.

 

Question 39. Succession in a fresh water ecosystem is
(a) Merosere
(b) Hydrosere
(c) Lithosere
(d) Halosere
Answer: (b) Hydrosere
In simple words: When plants grow in a freshwater ecosystem over time, it is known as hydrosere.

🎯 Exam Tip: Hydrosere specifically describes ecological succession that starts in a body of fresh water, moving towards a terrestrial environment.

 

Question 40. Study of interaction between living and non- living components is
(a) Biomass
(b) Food chain
(c) Food web
(d) Ecosystem
Answer: (d) Ecosystem
In simple words: The study of how living things and non-living things in an area interact is called an ecosystem.

🎯 Exam Tip: An ecosystem includes both biotic (living) and abiotic (non-living) factors and their complex interactions, which is its defining characteristic.

 

Question 41. Which of the following is not related to photosynthetic active radiation.
(a) 400-700 nm
(b) 10% is held by ozone
(c) 2-10% by green plants
(d) 46% reaches earth surface
Answer: (d) 46% reaches earth surface
In simple words: The idea that 46% of light reaches the Earth's surface is not directly about photosynthetic active radiation.

🎯 Exam Tip: Photosynthetically active radiation (PAR) specifically refers to the light spectrum (400-700 nm) used by plants for photosynthesis, not the total light reaching Earth.

 

Question 42. Which of the following light is efficient for photo-synthesis.
(a) Blue and red
(b) Blue and green
(c) Blue and white
(d) Blue and violet
Answer: (a) Blue and red
In simple words: Plants use blue and red light colors best for making food through photosynthesis.

🎯 Exam Tip: Chlorophyll, the main pigment in photosynthesis, absorbs blue and red light most effectively, reflecting green light, which is why plants appear green.

 

Question 43. Which of the following determine the productivity of different ecosystem.
(a) Fixation of radiant energy
(b) Population
(c) Size of ecosystem
(d) Number of plants
Answer: (a) Fixation of radiant energy
In simple words: How much sunlight energy an ecosystem can capture and use determines how productive it is.

🎯 Exam Tip: Productivity is fundamentally about the rate at which energy is converted into organic substances, primarily driven by solar (radiant) energy fixation.

 

Question 44. Which is the right representation of detritus food chain?
(a) Grass Earthworm → Black bird → Hawk
(b) Grass Mouse → Snake Eagle
(c) Fallen leaves → Earthworm → Black bird →Hawk
(d) Plants → Rabbit → Snake → Eagle
Answer: (c) Fallen leaves → Earthworm → Black bird →Hawk
In simple words: The correct detritus food chain starts with dead organic matter like fallen leaves, then goes to decomposers and scavengers.

🎯 Exam Tip: A detritus food chain always starts with dead organic matter, unlike a grazing food chain which begins with live producers.

 

Question 45. NPP of whole biosphere is estimated to be about billion tons dry weight/year
(a) 140
(b) 170
(c) 150
(d) 160
Answer: (b) 170
In simple words: The total net primary productivity for the entire Earth is roughly 170 billion tons of dry weight each year.

🎯 Exam Tip: Remember key figures like global NPP as they represent fundamental ecological quantities.

 

Question 46. NPP of oceanic producers is only billiob tons/year in unit time.
(a) 55
(b) 45
(c) 56
(d) 54
Answer: (a) 55
In simple words: The net primary productivity from producers in the oceans is about 55 billion tons per year.

🎯 Exam Tip: While oceans cover a large area, their productivity per unit area can be lower than terrestrial ecosystems, so remember the specific figures for oceanic NPP.

 

Question 47. During energy transfer from one trophic level to other only 10% stored at every level this is related to
(a) First law of thermodynamics
(b) Second law of thermodynamics
(c) Ten percent law
(d) Law of thermodynamics
Answer: (c) Ten percent law
In simple words: The rule that only 10% of energy moves up to the next level in a food chain is called the ten percent law.

🎯 Exam Tip: The 10% law is a fundamental concept in ecology for understanding energy flow through trophic levels and the limitations on food chain length.

 

Question 48. The commonly occurring pioneer species in xerich succession
(a) Lichens
(b) Mosses
(c) Bryophytes
(d) Pteridophytes
Answer: (a) Lichens
In simple words: The first living things to grow in dry places, like on bare rock, are usually lichens.

🎯 Exam Tip: Lichens are hardy pioneer species well-suited for colonizing barren, dry environments due to their ability to withstand harsh conditions.

 

Question 49. Lowest productivity is seen in
(a) Ocean
(b) Grass land
(c) forest
(d) savannah
Answer: (a) Ocean
In simple words: Oceans generally have the lowest productivity compared to land ecosystems.

🎯 Exam Tip: While vast, many parts of the open ocean have limited nutrient availability, leading to lower productivity per unit area compared to fertile land ecosystems.

 

Question 50. The term biosphere is used for
(a) Ecosystem
(b) Plants and animals
(c) All living organism
(d) The part of the earth with life
Answer: (d) The part of the earth with life
In simple words: The biosphere refers to all the places on Earth where life exists, from deep oceans to high in the atmosphere.

🎯 Exam Tip: Understand that the biosphere encompasses all ecosystems and living organisms on Earth, representing the global sum of all ecosystems.

 

Question 51. Bio geo chemical cycle refers to
(a) Cycling of nutrients
(b) Cycling of nutrients with ecosystem
(c) Water cycle
(d) Cycling of chemicals substrances
Answer: (b) Cycling of nutrients with ecosystem
In simple words: Biogeochemical cycles describe how important nutrients move through both living and non-living parts of an ecosystem.

🎯 Exam Tip: Biogeochemical cycles are fundamental processes that recirculate elements like carbon, nitrogen, and phosphorus, essential for life, throughout the Earth's systems.

 

Question 52. Which of the following does not contain phosphorous?
(a) Phospholipids
(b) DNA, RNA
(c) ATP, NADP
(d) Respiration
Answer: (d) Respiration
In simple words: Phosphorous is not directly involved in the process of respiration itself, unlike other biological molecules.

🎯 Exam Tip: Phosphorous is a key component of nucleic acids (DNA, RNA), energy carriers (ATP), and cell membranes (phospholipids), but not the direct process of respiration.

 

Question 53. The ecosystem with (or) without human interference is
(a) Terrestrial
(b) Natural
(c) Artificial
(d) Lotic
Answer: (b) Natural
In simple words: A natural ecosystem is one that exists without being changed or managed by people.

🎯 Exam Tip: Distinguish between natural ecosystems (formed without human intervention) and artificial or anthropogenic ecosystems (created or heavily modified by humans).

 

Question 54. Examine the ecological pyramid given below and select the type of it represent
(a) Upright pyramid of biomass
(b) Upright pyramid of number
(c) Inverted pyramid of biomass
(d) Inverted pyramid of number
Answer: (a) Upright pyramid of biomass
In simple words: This diagram shows a pyramid where the base is widest and gets narrower at the top. This shape represents how the total weight of living matter (biomass) decreases as you go up the food chain in most ecosystems.

🎯 Exam Tip: An upright pyramid of biomass means that the biomass of producers is greater than that of primary consumers, which is greater than secondary consumers, and so on, decreasing at higher trophic levels.

 

Question 55. The organisms which eat both plants and animals are called
Answer: Organisms that consume both plants and animals are called **omnivores**. This dietary flexibility allows them to use various food sources.
In simple words: Animals that eat both plants and other animals are known as omnivores.

🎯 Exam Tip: Clearly differentiate between herbivores (plant-eaters), carnivores (meat-eaters), and omnivores (both plant and meat-eaters) to correctly classify organisms in a food web.

 

Question 56. When sparrow eats insects and worms it is a
(a) Primary consumer
(b) Secondary consumer
(c) Tertiary consumer
(d) Carnivore
Answer: (b) Secondary consumer
In simple words: When a sparrow eats insects and worms, which are primary consumers, the sparrow acts as a secondary consumer.

🎯 Exam Tip: An organism's trophic level can change depending on what it is eating; if it eats a herbivore (primary consumer), it becomes a secondary consumer.

 

Question 57. Imagine number of fruit eating birds and insects feeding or a big tree what kind of pyramid would be ?
(a) Inverted pyramid of number
(b) Inverted pyramid of energy
(c) Upright pyramid
(d) Upright pyramid of energy
Answer: (a) Inverted pyramid of number
In simple words: If many birds and insects feed on just one big tree, the pyramid of numbers would be upside down because there's one producer supporting many consumers.

🎯 Exam Tip: A pyramid of numbers can be inverted when a single large producer (like a tree) supports a large number of smaller primary consumers (like insects and birds).

 

Question 58. Which of the following is natural ecosystem.
(a) Pond and lake
(b) Rice field
(c) Maize fi eld
(d) Aquarium
Answer: (a) Pond and lake
In simple words: Ponds and lakes are examples of ecosystems that form naturally without human intervention.

🎯 Exam Tip: Natural ecosystems develop without significant human influence, whereas rice fields, maize fields, and aquariums are artificial or human-modified ecosystems.

 

Question 59. Which one of the following food chain refers inverted pyrmid? Q23D
(a) Grasses → Rats → Snake → Hawk
(b) Banyan tree → Birds → Beetles → Fungi
(c) Phytoplanktons → Zooplanktons → Fishes → snakes
(d) Plants Rabbits → Fox → Hawk
Answer: (c) Phytoplanktons → Zooplanktons → Fishes → snakes
In simple words: A food chain starting with tiny organisms and leading to larger ones, like in water, often shows an inverted pyramid of biomass.

🎯 Exam Tip: In aquatic ecosystems, the pyramid of biomass can be inverted because phytoplankton (producers) have a very short lifespan and reproduce quickly, supporting a larger biomass of zooplankton (consumers).

 

Question 60. The quantity of energy present in the universe is constant it is related to
(a) Second law of thermodynamics
(b) First law of thermodynamics
(c) Ten percent lawd. Law of thermodynamics
Answer: (b) First law of thermodynamics
In simple words: The idea that energy cannot be created or destroyed, only changed from one form to another, is the first law of thermodynamics.

🎯 Exam Tip: The First Law of Thermodynamics, also known as the Law of Conservation of Energy, is fundamental to understanding energy flow in ecosystems.

II. Two Marks

 

Question 1. What do you mean standing quality (or) Standing state of abiotic components ?
Answer: Abiotic components play a crucial role in any ecosystem. The standing quality, or standing state, refers to the total amount of inorganic substances present in an ecosystem at a particular moment. These substances, like nutrients, are essential for life.
In simple words: Standing state is the total amount of non-living chemicals and nutrients found in an ecosystem at any given time.

🎯 Exam Tip: Remember that "standing state" specifically refers to inorganic nutrients in an ecosystem, while "standing crop" refers to living biomass.

 

Question 2. In most of the ecosystem, which one is called autotrophs why?
Answer: In most ecosystems, green plants are called autotrophs. This is because autotrophs are organisms that can create their own organic compounds (food) from simple inorganic substances, typically through photosynthesis. For example, green plants use sunlight, water, and carbon dioxide to produce their own food.
In simple words: Green plants are called autotrophs because they make their own food using sunlight.

🎯 Exam Tip: Autotrophs are always at the base of the food chain, converting raw energy (like sunlight) into usable chemical energy for other organisms.

 

Question 3. What is standing crop?
Answer: Standing crop refers to the total amount of living materials present in a population or ecosystem at a specific time. It represents the biomass of the organisms. This quantity is often measured in terms of number or biomass per unit area.
In simple words: Standing crop is the total amount of living matter or biomass in an area at one specific moment.

🎯 Exam Tip: Standing crop is a measure of the existing biomass, not the rate of production, which is productivity.

 

Question 4. What are the functions of an ecosystem?
Answer: An ecosystem performs several important functions. Firstly, it involves the creation and sharing of energy among its various components. Secondly, it facilitates the cycling of essential materials between the living (biotic) and non-living (abiotic) parts of the ecosystem, ensuring continuous availability of nutrients.
In simple words: Ecosystems create and share energy, and they move materials between living and non-living parts.

🎯 Exam Tip: The two main functional aspects of an ecosystem are energy flow (one-way) and nutrient cycling (circular).

 

Question 5. Why biomass production is called productivity of an ecosystem?
Answer: Biomass production is called the productivity of an ecosystem because it measures the rate at which new organic matter (biomass) is created by organisms. Productivity indicates how much energy is captured and stored by producers, and then transferred through the food web. It can be expressed as grams per square meter per year (gm/m2/yr) or kilocalories per square meter per year (kcal/m2/yr).
In simple words: Biomass production is called productivity because it shows how fast an ecosystem makes new living material or energy over time.

🎯 Exam Tip: Productivity is a rate (per unit area per unit time), while biomass is a standing crop (amount at a specific time).

 

Question 6. What is biomass? How it is measured?
Answer: Biomass is the total quantity or weight of all living organisms in a given area. It represents the accumulated organic matter. Biomass can be measured in several ways: as fresh weight, dry weight, or the carbon weight of the organisms. Dry weight is often preferred as it removes water content, providing a more consistent measure of organic matter.
In simple words: Biomass is the total weight of all living things in an area, measured by their fresh weight, dry weight, or carbon content.

🎯 Exam Tip: Always specify "dry weight" when discussing biomass in ecological studies, as it gives a more accurate representation of organic matter content by eliminating water variability.

 

Question 7. Write the difference between gross primary productivity and gross secondary productivity ?
Answer:Grass Primary Productivity: 1. This is the total amount of food energy or biomass created by autotrophs (like plants) in an ecosystem. 2. It is achieved through the process of photosynthesis. Grass Secondary Productivity: 1. This refers to the total amount of plant material eaten by herbivores, minus any waste materials like faeces. 2. It is carried out by herbivores through the process of ingestion. The key difference is that primary productivity is about producers making their own food, while secondary productivity is about consumers eating that food.
In simple words: Gross primary productivity is all the food plants make. Gross secondary productivity is all the food that plant-eaters consume and keep.

🎯 Exam Tip: Remember that primary productivity occurs at the producer level (autotrophs), while secondary productivity occurs at the consumer level (heterotrophs).

 

Question 8. Differentiate net primary productivity from net secondary productivity ?
Answer:Net Primary Productivity (NPP): 1. This is the portion of energy that remains in the plant after it has used some for its own respiration. 2. Net primary productivity is calculated based on the activities of producers. Net Secondary Productivity (NSP): 1. This is the stored energy or biomass per unit area per unit time in consumers, after they have used some energy for their own respiration. 2. Net secondary productivity is calculated based on the activities of consumers. Essentially, both are "net" because they account for energy lost through respiration, but NPP is for producers and NSP is for consumers.
In simple words: Net primary productivity is the energy left in plants after they breathe. Net secondary productivity is the energy left in animals after they breathe.

🎯 Exam Tip: Both net primary and net secondary productivity subtract respiratory losses from the total (gross) productivity, representing the energy available to the next trophic level.

 

Question 10. Which factors may affect the primary productivity of plants (or) producers ?
Answer: The primary productivity of plants, or producers, is influenced by several factors: - **Plant species of an area:** Different plant types have varying photosynthetic efficiencies. - **Photosynthetic capacity:** How well plants can perform photosynthesis. - **Availability of nutrients:** Essential minerals like nitrogen and phosphorus are crucial for plant growth. - **Solar radiation:** The amount of sunlight available directly impacts photosynthesis. - **Precipitation:** Water availability is vital for plant survival and growth. - **Soil type:** Soil structure, texture, and water-holding capacity affect root development and nutrient uptake. - **Topographic factors:** Features like altitude and slope can influence light exposure and water drainage. - **Environmental factors:** General climate conditions, temperature, and other local environmental variables also play a role. All these factors work together to determine how much new plant material can be produced.
In simple words: Many things affect how much food plants make, such as the type of plant, how much sunlight and water they get, the soil quality, and local weather.

🎯 Exam Tip: Remember that primary productivity is a complex process influenced by a combination of biotic factors (plant type) and abiotic factors (light, water, nutrients, temperature).

 

Question 11. How does NPP calculated from GPP?
Answer: Net Primary Productivity (NPP) is calculated from Gross Primary Productivity (GPP) by subtracting the energy lost during the producers' respiration (R). So, the formula is:
\( NPP = GPP - R \) This means NPP is the energy remaining after plants use some of the energy they produced for their own life processes, making it the energy available for the next trophic level.
In simple words: You calculate Net Primary Productivity by taking the total energy made by plants (Gross Primary Productivity) and subtracting the energy they use for breathing.

🎯 Exam Tip: Always remember the formula \( NPP = GPP - R \); it's crucial for understanding energy dynamics in ecosystems.

 

Question 12. Why grey carbon different from brown carbon?
Answer: Grey carbon and brown carbon differ in their source and storage. - **Grey carbon** refers to carbon stored in fossil fuels such as coal, oil, and biogas deposits within the Earth's lithosphere. It is essentially ancient organic matter. - **Brown carbon** is carbon stored in industrialized forest wood, which is then used to make commercial articles like furniture or building materials. This carbon is sequestered through recent plant growth. The main difference is the timescale and origin: grey carbon is very old, naturally formed underground, while brown carbon is more recent and linked to managed forests and human use.
In simple words: Grey carbon is old carbon found in fuels like coal underground, while brown carbon is newer carbon stored in wood used for products.

🎯 Exam Tip: Differentiating carbon types helps in understanding different carbon pools and their roles in the global carbon cycle and human impact.

 

Question 13. What are the sources for blue carbon and black carbon
Answer: Blue carbon and black carbon originate from different sources: - **Blue carbon** is carbon stored in the atmosphere. This carbon is mainly in the form of carbon dioxide and is part of the atmospheric carbon pool, which interacts with oceans and terrestrial ecosystems. - **Black carbon** is a component of fine particulate matter formed from the incomplete burning of fossil fuels (like diesel engine gas) and biomass (like coal fired power plants). It is a major air pollutant. These different forms highlight various carbon storage and emission processes.
In simple words: Blue carbon comes from carbon stored in the air. Black carbon is released when fuels like diesel or coal are burned incompletely.

🎯 Exam Tip: Be precise with the definitions of different 'colors' of carbon, as they represent distinct forms, sources, and environmental impacts.

 

Question 14. What is energy flow ?
Answer: Energy flow is the process by which energy is transferred between different trophic levels within an ecosystem. It starts with producers capturing energy (usually from the sun) and moves through consumers. This flow of energy is a one-way process, not a cycle, and it is a fundamental function in any ecosystem as it sustains all life.
In simple words: Energy flow is how energy moves from one living thing to another in an ecosystem, usually starting from plants.

🎯 Exam Tip: Remember that energy flow is unidirectional (one-way), meaning energy is lost as heat at each transfer and is not recycled, unlike nutrients.

 

Question 15. If crow is absent in an ecosystem what would happen?
Answer: If crows were absent from an ecosystem, several changes would occur: - Crows are omnivores, eating cereals, fruits, seeds, insects, and worms. Their absence would impact these populations. - They are also scavengers, eating dead and decaying animals, which helps keep the environment clean. Without them, there might be an increase in carcasses and associated diseases. - Crows occupy various trophic levels in the food chain, so their removal would disrupt energy transfer. - They help disperse seeds when they eat fruits. Fewer crows could mean less seed dispersal for some plants. Ultimately, the ecosystem would experience drastic impacts, and other organisms might evolve to fill the vacant ecological niche previously occupied by crows. For example, specific plant species that rely on crows for pollination or seed dispersal could face extinction if no other animal steps in.
In simple words: If crows disappear, the ecosystem would become unbalanced because crows eat many different things, help clean up, and spread seeds. Other animals might have to take over their roles.

🎯 Exam Tip: Consider the multiple roles an omnivorous species like a crow plays in an ecosystem-as a predator, scavenger, and seed disperser-when analyzing the impact of its removal.

 

Question 17. Conversion of light energy into chemical energy which law is related to this ?
Answer: The first law of thermodynamics explains this process. It describes how light energy changes into chemical energy during photosynthesis, where plants use carbon dioxide and water to create glucose and oxygen.
\( 6CO_2 + 6H_2O \xrightarrow{\text{Light}} C_6H_{12}O_6 + O_2 \)
This fundamental process is crucial for life on Earth, converting sunlight into food energy.
In simple words: The first law of thermodynamics explains how light energy becomes chemical energy during photosynthesis. Plants turn sunlight, water, and CO2 into sugar and oxygen.

🎯 Exam Tip: Remember that photosynthesis is a prime example of the first law of thermodynamics in action, showing energy transformation rather than creation or destruction.

 

Question 18. Construct the diagrammatic representation of grazing food chain.
Answer: A grazing food chain starts with producers that make their own food using sunlight. Energy then moves from these producers to herbivores, then to smaller carnivores, and finally to top carnivores. The sun is the primary source of energy for this food chain.

In simple words: This diagram shows a grazing food chain. The sun gives energy to grass, grass is eaten by a grasshopper, the grasshopper is eaten by a frog, and the frog is eaten by a snake. Each arrow shows where the energy goes.

🎯 Exam Tip: When drawing a food chain, always ensure arrows point from the organism being eaten to the organism that eats it, indicating the direction of energy flow.

 

Question 19. Draw the diagrammatic representation of detritus food chain.
Answer: A detritus food chain starts with dead organic matter, which is then broken down by decomposers. These decomposers are eaten by other organisms, transferring energy through the ecosystem. This chain is essential for nutrient recycling.

In simple words: This diagram shows a food chain that starts with dead stuff like fallen leaves. Earthworms eat the dead leaves, then a black bird eats the earthworm, and finally, a hawk eats the black bird. It's how nutrients get recycled in nature.

🎯 Exam Tip: The detritus food chain is critical for nutrient cycling; always highlight its starting point (dead organic matter) and the role of decomposers and detritivores.

 

Question 20. Food web is known as basic unit of ecosystem. Why ?
Answer: A food web is made up of many food chains that are linked together in a complex network. It is considered a basic unit of an ecosystem because it helps keep nature stable by showing all the possible feeding relationships. This stability is called homeostasis, meaning the ecosystem maintains its balance despite changes.
In simple words: A food web is a network of many food chains. It's key to an ecosystem because it keeps nature stable and balanced, like how a healthy body keeps itself working well.

🎯 Exam Tip: Explain that food webs provide more stability than simple food chains because they offer alternative food sources, making the ecosystem more resilient to disturbances.

 

Question 21. Why ecological pyramids are called Eltonianpyramids ?
Answer: Ecological pyramids are known as Eltonian pyramids because Charles Elton first introduced the idea of these pyramids in 1927. He showed how the number, biomass, or energy of organisms changes at different levels in an ecosystem.
In simple words: Ecological pyramids are called Eltonian pyramids because Charles Elton was the first to talk about them in 1927. He showed how living things are arranged in layers, like a pyramid.

🎯 Exam Tip: Mentioning Charles Elton and the year 1927 is key to scoring full marks when explaining the origin of the term "Eltonian pyramids."

 

Question. What is ecological pyramid ?
Answer: An ecological pyramid is a picture that shows the feeding structure and how things work at different levels in an ecosystem. It visually represents the relationships between producers, consumers, and decomposers, showing how their numbers, biomass, or energy change at each level.
In simple words: An ecological pyramid is a chart that shows how many living things, how much they weigh, or how much energy they have at each level in a food chain.

🎯 Exam Tip: Clarify that ecological pyramids can represent numbers, biomass, or energy, and that each type offers a different insight into ecosystem structure.

 

Question 23. Why the pyramids of energy is always upright?
Answer: Energy pyramids are always upright because energy decreases as it moves up from one feeding level to the next. Producers have the most energy, and less energy is available for each level above them. This happens because a lot of energy is lost as heat during metabolic processes like respiration at each transfer. Therefore, higher trophic levels have less energy available to them.
In simple words: Energy pyramids are always upright because energy is lost at each step up the food chain. Producers have the most energy, and only a little bit passes to each level above them.

🎯 Exam Tip: Emphasize the "10 percent law" of energy transfer, where only about 10% of energy moves to the next trophic level, which directly explains the upright shape.

 

Question 24. Define pyramid of energy.
Answer: A pyramid of energy is a diagram that shows how energy flows through each feeding level in an ecosystem. It measures the amount of energy at each trophic level, typically in units like calories or joules. This type of pyramid helps us see how much energy is available at each step, from plants to top predators.
In simple words: A pyramid of energy shows how much energy is available at each level of a food chain in an ecosystem.

🎯 Exam Tip: Always specify that energy pyramids measure the rate of energy flow (e.g., per unit area per unit time), not just the total amount, which is a common misconception.

 

Question 25. Name the process which is essential for recycling and balancing the nutrient in an ecosystem?
Answer: Decomposition is the process that is essential for recycling nutrients and keeping an ecosystem balanced. In this process, decomposers, such as bacteria and fungi, break down dead organic matter into simpler substances. This allows nutrients to be reused by plants and other organisms, maintaining the ecosystem's health.
In simple words: Decomposition is the process that recycles nutrients in an ecosystem. Decomposers break down dead things, so their nutrients can be used again.

🎯 Exam Tip: Highlight decomposers (bacteria and fungi) as key organisms in decomposition, as their role is central to nutrient cycling.

 

Question 26. Write the difference between limnology and oceanography ?
Answer: Limnology is the study of the biological, chemical, physical, and geological parts of freshwater ecosystems on land, like ponds and lakes. Oceanography, on the other hand, is the study of the same aspects but for marine ecosystems, which are oceans. Limnology helps us understand freshwater life, while oceanography focuses on the vast marine environment and its processes.
In simple words: Limnology is the study of freshwater bodies like lakes and ponds. Oceanography is the study of oceans. They both look at the living and non-living parts but in different types of water.

🎯 Exam Tip: Clearly differentiate between the "inland fresh water aquatic ecosystem" for limnology and "ocean" for oceanography in your answer.

 

Question 27. Blue carbon ecosystems are very important to nature. Why?
Answer: Blue carbon ecosystems are vital because they are excellent at storing carbon. Coastal ecosystems like seagrass beds and mangrove forests capture and store large amounts of carbon dioxide from the atmosphere very effectively. These ecosystems help reduce greenhouse gases and support marine life, playing a crucial role in mitigating climate change.
In simple words: Blue carbon ecosystems like seagrass and mangroves are important because they are very good at soaking up and storing carbon from the air. This helps fight climate change and keeps the sea healthy.

🎯 Exam Tip: Focus on "carbon sequestration" and specific examples like "seagrasses and mangroves" when explaining the importance of blue carbon ecosystems.

 

Question 28. What is carbon sequestration?
Answer: Carbon sequestration is the natural or artificial process of capturing and storing carbon dioxide from the atmosphere. It involves trapping CO2 in places like oceans, forests, or underground geological formations. This process helps reduce the amount of greenhouse gases in the air, thereby slowing down global warming.
In simple words: Carbon sequestration is when carbon dioxide from the air is captured and stored, for example, in trees or oceans. It helps clean the air.

🎯 Exam Tip: Define "carbon sequestration" clearly as the process of "capturing and storing" CO2 and provide examples of "carbon sinks" like oceans and forests.

 

Question 29. Odd one out and give reason. Provision of habitat, nutrient recycling, primary production, succession Odd one out: Succession. Reason : Replacement of one type of plant community by other of the same place is known as succession. While others are supporting services of ecosystem services.
Answer: The odd one out is "Succession". The reason is that succession refers to the process where one type of plant community is replaced by another in the same area over time. The other options-provision of habitat, nutrient recycling, and primary production-are all supporting services provided by an ecosystem, which help maintain life and ecological processes.
In simple words: "Succession" is the odd one out. It means how plant groups change over time. The others are services an ecosystem gives, like places to live and making food.

🎯 Exam Tip: Distinguish between ecological "processes" (like succession) and "services" (benefits humans get from ecosystems) for clarity.

 

Question 30. Odd one out and give reason. Lichen, blue green algae, green algae diatoms, bacteria. Answer: Odd one out: Lichen Reason : Lichen is related to primary succession. While others are related to phytoplankton stage of hydrosere.
Answer: The odd one out is "Lichen". The reason is that lichens are typically associated with primary succession, being among the first organisms to colonize barren land. The others-blue-green algae, green algae, diatoms, and bacteria-are all types of microorganisms found in the phytoplankton stage of hydrosere, which is ecological succession occurring in water.
In simple words: "Lichen" is the odd one out. Lichens grow first on bare land. The other things are tiny living organisms found in the water during early plant growth stages.

🎯 Exam Tip: Accurately linking lichens to "primary succession" and the other organisms to the "phytoplankton stage of hydrosere" is crucial for a complete answer.

 

Question 31. Write the slogan for the safety of the environment.
Answer: A good slogan for environmental safety is: "Use Ecosystem. But don't lose ecosystem. Make it sustainable.” This encourages responsible use and long-term care of natural systems, ensuring they can continue to provide for future generations.
In simple words: A good slogan is: "Use nature wisely, don't destroy it. Keep it healthy for the future."

🎯 Exam Tip: Slogans should be concise, impactful, and easy to remember, focusing on key themes like conservation, sustainability, or responsibility.

 

Question 32. Define fragmentation.
Answer: Fragmentation is the process where detritivores, such as bacteria, fungi, and earthworms, break down large pieces of dead organic matter (detritus) into smaller particles. This initial step in decomposition makes it easier for other organisms to break down the material further, speeding up the nutrient cycling process.
In simple words: Fragmentation is when tiny creatures like worms and bacteria break down dead leaves and plants into smaller bits.

🎯 Exam Tip: Remember that fragmentation is the *physical* breakdown of detritus into smaller pieces, increasing its surface area for further microbial action.

 

Question 33. What is Humification?
Answer: Humification is the process where simplified detritus-dead organic material-is converted into a dark-colored, shapeless substance called humus. Humus is very stable and important for soil fertility, as it improves soil structure and water retention.
In simple words: Humification is when dead plants and animals turn into a dark, rich soil material called humus.

🎯 Exam Tip: Key points for humification are the formation of "dark-colored amorphous substance" (humus) and its resistance to microbial action, contributing to soil fertility.

 

Question 34. Define oceanography.
Answer: Oceanography is the scientific study of the ocean. It looks at all parts of the ocean, including its living creatures (biological), the chemicals in the water (chemical), the waves and currents (physical), and the seafloor (geological). This field helps us understand how oceans work and their importance to global climate and ecosystems.
In simple words: Oceanography is the study of oceans, including the plants, animals, water, and land under the sea.

🎯 Exam Tip: Ensure you include the four main aspects of oceanography: biological, chemical, physical, and geological, to provide a comprehensive definition.

 

Question 35. In different food chains of different ecosystem the placement of man is not mentioned. You give placement in a suitable food chain and give reason for your answer.
Answer: The placement of humans in a food chain is not fixed because of our diverse diets. Since humans are omnivores, eating both plants and animals, we can occupy different trophic levels. For example, if we eat plants (like vegetables), we are primary consumers (second trophic level). If we eat herbivores (like a cow), we become secondary consumers (third trophic level). If we eat carnivores (like salmon, which eats smaller fish), we are tertiary consumers (fourth trophic level). Our position depends on what we choose to eat.
In simple words: Humans can be at different places in a food chain because we eat both plants and animals. If we eat plants, we are at one level. If we eat animals that eat plants, we are at a higher level.

🎯 Exam Tip: When discussing human trophic levels, provide clear examples for each level (herbivore, carnivore, omnivore behavior) to illustrate flexibility.

 

III. Three Marks

 

Question 1. What is photosynthetically active radiation ?
Answer: Photosynthetically Active Radiation (PAR) is the specific range of light wavelengths, from 400 to 700 nanometers, that plants use for photosynthesis. This light is what plants convert into energy to make their food. Plants mostly absorb blue and red light for this process, and typically only 2-10% of the sun's total energy is used for photosynthesis, with the rest being reflected or dissipated.
In simple words: Photosynthetically Active Radiation is the special light, between 400 and 700 nm, that plants use to make food. Plants mostly use blue and red light, but only a small part of the sun's energy for this.

🎯 Exam Tip: Clearly state the wavelength range (400-700 nm) and the percentage of solar energy utilized (2-10%) as these are specific details examiners look for.

 

Question 2. Differentiate green carbon from grey carbon.
Answer: Green carbon is the carbon stored in the Earth's living parts, like plants and soil (the biosphere). It is captured through photosynthesis by green plants, playing a vital role in the global carbon cycle. Grey carbon, on the other hand, is carbon stored in fossil fuels such as coal, oil, and biogas, which are found deep within the Earth's crust (lithosphere). It forms over millions of years through geological processes after the decomposition of ancient organic matter.
In simple words: Green carbon is carbon stored in living things and soil through plant growth. Grey carbon is carbon stored in fossil fuels deep underground.

🎯 Exam Tip: Emphasize that green carbon involves *biological* processes like photosynthesis, while grey carbon involves *geological* storage in fossil fuels.

 

Question 3. Differentiate primary productivity from secondary productivity.
Answer:

In simple words: Primary productivity is how much food plants make. Secondary productivity is how much energy animals store after eating plants or other animals.

🎯 Exam Tip: Clearly define each term and state the organisms involved (autotrophs for primary, heterotrophs for secondary) to ensure a complete differentiation.

 

Question 4. "The energy transformation results in the education of the free energy of the system". What does it states ?
Answer: This statement refers to the second law of thermodynamics. It means that when energy changes from one form to another in a system, some energy is always lost as unusable heat, making the transformation less than 100% efficient. This principle explains why ecosystems need a continuous input of energy and why energy flow is unidirectional.
In simple words: This means the second law of thermodynamics. It says that when energy changes form, some of it is always lost as heat, so energy changes are never perfectly efficient.

🎯 Exam Tip: Link the concept of "free energy" directly to the second law of thermodynamics and the inefficiency of energy transformations, especially in biological systems.

 

Question 5. What is ten percent law?
Answer: The Ten Percent Law, proposed by Lindeman in 1942, states that only about 10% of the energy from one trophic level is transferred to the next level. The remaining 90% is lost as heat during metabolic processes like respiration or through decomposition. This explains why food chains rarely have more than four or five trophic levels, as available energy decreases significantly at each step.
In simple words: The Ten Percent Law says that only 10% of energy moves from one step to the next in a food chain. Most of the other 90% is lost as heat.

🎯 Exam Tip: Mentioning Lindeman (1942) and the exact percentage (10% transfer, 90% loss as heat) is crucial for a precise answer on the Ten Percent Law.

 

Question 6. Which type of food chain is present in all ecosystem ? (or) What is detritus food chain?
Answer: The detritus food chain is present in all ecosystems. This type of food chain starts with dead organic matter, which is a key source of energy. Energy then moves from detritus to detritivores (like earthworms), then to small carnivores, and finally to top carnivores. It is crucial for recycling nutrients and supports a vast array of organisms.
In simple words: The detritus food chain is in every ecosystem. It starts with dead plants and animals. Decomposers eat them, and then other animals eat the decomposers, recycling energy.

🎯 Exam Tip: Distinguish the detritus food chain from the grazing food chain by emphasizing its starting point (dead organic matter) and its critical role in decomposition and nutrient cycling.

 

Question 7. Complete the missing organisms of food web in grassland ecosystem.
Answer: The missing organisms in the grassland food web are:
1. A - Rabbit
2. B - Mouse
These organisms act as primary consumers, feeding on plants and becoming a food source for higher trophic levels in the ecosystem.
In simple words: For the grassland food web, the missing animals are: 1. Rabbit (A) 2. Mouse (B). They eat plants.

🎯 Exam Tip: When completing food webs, consider the typical diet of common grassland animals to correctly identify the missing links and their trophic levels.

 

Question 8. What are the importance of studying food web ? (or) What are significant of food web? Is there any significance in maintaining food web?
Answer: Studying food webs is important because they show how different species interact in an ecosystem, both directly and indirectly. They help us understand how a change in one species can affect others throughout the entire community. Food webs also reveal how energy moves and is transferred through various feeding levels in both land and water environments, showing the complex balance of nature. Maintaining healthy food webs ensures ecosystem stability and resilience.
In simple words: Studying food webs is important to see how all living things in an ecosystem are connected. It shows how energy moves and how changes to one animal can affect many others. Keeping them healthy keeps nature balanced.

🎯 Exam Tip: When explaining the significance of food webs, emphasize "interconnectedness," "energy transfer patterns," and "ecosystem stability" as key concepts.

 

Question 9. What are the different shapes of pyramids present in pyramids of number?
Answer: Pyramids of number can have three different shapes depending on the ecosystem: * **Upright:** In grassland and pond ecosystems, the pyramid is typically upright, with many producers at the base and fewer organisms at higher trophic levels. * **Spindle-shaped:** In a forest ecosystem, the pyramid is spindle-shaped, with a few large producers (trees) supporting many herbivores, and then fewer carnivores. * **Inverted:** In a parasite ecosystem, the pyramid is inverted, as a single host can support many parasites, which in turn might support hyper-parasites.
In simple words: Pyramids of number can be upright (like in grasslands), spindle-shaped (like in forests), or inverted (like with parasites). This shows how the count of living things changes at each step.

🎯 Exam Tip: Provide a specific example for each shape (grassland/pond for upright, forest for spindle, parasite for inverted) to clearly illustrate the concept.

 

Question 10. What are the different shapes of pyramids present in pyramid of biomass?
Answer: Pyramids of biomass show the total mass of living organisms at each trophic level. * **Upright:** In grassland and forest ecosystems, these pyramids are usually upright, with the largest biomass at the producer level (grasses, trees) supporting progressively smaller biomasses of consumers. * **Inverted:** In pond ecosystems, the pyramid of biomass is often inverted, meaning a smaller biomass of producers (phytoplankton) at any given time supports a larger biomass of primary consumers (zooplankton). This is because phytoplankton reproduce and are consumed very quickly.
In simple words: Biomass pyramids can be upright (like in forests) or inverted (like in ponds). Upright means more weight at the bottom; inverted means less weight at the bottom.

🎯 Exam Tip: When explaining inverted biomass pyramids (e.g., in ponds), emphasize the rapid turnover rate of producers as the key reason for their smaller biomass at the base.

 

Question 11. Why pyramids of biomass in grass land and forest ecosystem is always upright ?
Answer: Pyramids of biomass in grassland and forest ecosystems are always upright because the total mass of organisms decreases as you move up the food chain. Producers, like grasses and trees, have the largest biomass, supporting smaller biomasses of herbivores, which in turn support even smaller biomasses of carnivores. This steady decrease in biomass from the base to the top causes the pyramid to stand upright, reflecting the flow of energy.
In simple words: In grasslands and forests, the biomass pyramid is upright because there's a lot more plant mass than animal mass. The weight of living things gets smaller as you go up the food chain.

🎯 Exam Tip: Connect the upright shape directly to the general rule that a large quantity of producers is needed to sustain a smaller quantity of consumers at each successive level.

 

Question 12. Why pyramids of biomass in pond ecosystem is always inverted in shape?
Answer: In a pond ecosystem, the pyramid of biomass is inverted because the producers, such as phytoplankton, are very small and have a low collective biomass at any given time. These tiny producers reproduce quickly but are rapidly consumed by a larger biomass of primary consumers (zooplankton). This means the biomass at the base is less than the level above it, making the pyramid appear upside down.
In simple words: Pond biomass pyramids are upside down because tiny plants (producers) weigh less than the small animals that eat them. The tiny plants grow fast but are eaten quickly.

🎯 Exam Tip: The key reason for an inverted biomass pyramid in ponds is the *short lifespan and rapid turnover* of phytoplankton, not their individual size.

 

Question 13. Differentiate humification and mineralisation.
Answer:

In simple words: Humification turns dead stuff into stable humus, which is good for soil. Mineralization breaks down humus to release nutrients for plants.

🎯 Exam Tip: Focus on the *product* of humification (humus) and the *outcome* of mineralization (release of inorganic nutrients) for clear differentiation.

 

Question 14. Define catabolism:
Answer: Catabolism is the process where decomposers, such as bacteria and fungi, release extracellular enzymes into their surroundings. These enzymes then break down complex organic and inorganic compounds into simpler substances. This is a key part of decomposition, as it helps recycle nutrients within the ecosystem.
In simple words: Catabolism is when decomposers use special enzymes to break down big, complex materials into smaller, simpler ones.

🎯 Exam Tip: Highlight that catabolism involves the *breakdown* of complex substances into simpler ones, often by *enzymes* from decomposers.

 

Question 15. What is leaching or eluviation ? (or) Which process of decomposition helpful to enrich lower layer of soil ?
Answer: Leaching, also known as eluviation, is the process where water-soluble organic and inorganic compounds, formed during decomposition, are carried by water from the upper layers of the soil to deeper layers. This movement helps distribute nutrients within the soil profile, often enriching the lower layers where they can be stored or taken up by plant roots.
In simple words: Leaching (or eluviation) is when rain or water washes nutrients and other dissolved things from the top soil down to deeper soil layers.

🎯 Exam Tip: Emphasize the role of *water* in transporting *soluble* compounds downwards through the soil profile during leaching/eluviation.

 

Question 16. What is bio-geo chemical cycle ?
Answer: A biogeochemical cycle describes how essential chemical elements, like carbon, nitrogen, and water, move through the living (bio) and non-living (geo) parts of Earth. These cycles involve continuous exchange of materials between the atmosphere, oceans, land, and organisms. They are vital for the continuous availability of nutrients required for life.
In simple words: A biogeochemical cycle is how important chemicals like carbon and water move around between living things and non-living things (like air, water, and land) on Earth.

🎯 Exam Tip: Break down the term "biogeochemical" into "bio" (life), "geo" (Earth), and "chemical" to help explain its meaning, and list examples of elements involved.

 

Question 17. Which cycles are called sedimentary cycles ? Why?
Answer: Cycles for elements like phosphorus, sulfur, and calcium are called sedimentary cycles. This is because these elements are mainly found in solid forms as sediments in rocks and soil on Earth, rather than in the atmosphere. These cycles are very slow because nutrients can get trapped in these large geological reservoirs for long periods, making their circulation much slower than gaseous cycles.
In simple words: Phosphorus, sulfur, and calcium cycles are called sedimentary cycles because these elements are mostly found in rocks and soil. They are very slow because the nutrients can get stuck in the ground for a long time.

🎯 Exam Tip: The key characteristic of sedimentary cycles is that their main reservoir is the Earth's crust (rocks and sediments), not the atmosphere, leading to slow circulation.

 

Question 18. Wihat is carbon cycle?
Answer: The carbon cycle is the natural process by which carbon atoms are continuously exchanged between living organisms and the environment. It involves two main, opposite processes: photosynthesis, where plants take in carbon dioxide, and respiration, where organisms release carbon dioxide. This constant movement ensures carbon is available for all life forms and helps regulate Earth's climate.
In simple words: The carbon cycle is how carbon moves between living things and the air. Plants take in carbon dioxide, and living things release it back out.

🎯 Exam Tip: Focus on the main exchange points of carbon (atmosphere, organisms, oceans) and the key biological processes (photosynthesis and respiration) that drive the cycle.

 

Question 19. What is ecosystem resilience ? (or) Ecosystem robustness?
Answer: Ecosystem resilience, also known as ecosystem robustness, is the ability of an ecosystem to withstand disturbances and recover quickly from damage. When events like fires, floods, or disease remove a lot of biomass, a resilient ecosystem can bounce back and return to its original state or a new stable state, maintaining its functions and structure. This capability is vital for long-term survival.
In simple words: Ecosystem resilience is how well an ecosystem can handle big problems like fire or flood and then get back to normal quickly.

🎯 Exam Tip: Define resilience as the ability to "resist damage" and "recover quickly," highlighting that it's about bouncing back from disturbances.

 

Question 20. What are the ways to go green and save green?
Answer: To live a more environmentally friendly life and protect our planet, we can adopt several practices. These include conserving water by turning off taps when not needed, saving electricity by switching off unused gadgets, never using plastics and replacing them with biodegradable products, and always choosing eco-friendly technology and products. These simple actions help reduce our impact on the environment and conserve resources.
In simple words: To save the environment, we should save water, turn off unused electricity, use less plastic, and pick products that are kind to the Earth.

🎯 Exam Tip: For practical environmental tips, focus on actionable items related to conservation (water, energy) and responsible consumption (plastics, eco-friendly products).

 

Question 21. Draw and write the 3 Rs for the safety and benefits of the environment.
Answer: The "3 Rs" for environmental safety are Reduce, Reuse, and Recycle. These principles guide us to change our lifestyle for the benefit of the environment: * **Reduce:** This means using less of everything. For example, buying fewer items or choosing products with less packaging. This is the most effective R as it prevents waste from being created. * **Reuse:** This involves finding new ways to use things instead of throwing them away. For example, using reusable bags, refilling water bottles, or donating old clothes. * **Recycle:** This is turning old items into new ones. For example, sending plastic bottles or paper to be processed into new products. This conserves raw materials and energy.

In simple words: The "3 Rs" are Reduce (use less), Reuse (use again), and Recycle (make new things from old). They help keep our environment clean and healthy.

🎯 Exam Tip: Always define each "R" clearly and provide a practical example for each to demonstrate understanding of their environmental benefit.

 

Question 22. Which is significance of food web?
Answer: Food webs are important for several reasons. They show how species directly interact (e.g., predator-prey relationships) and how indirect interactions can affect an ecosystem. Food webs help scientists understand how changes at the bottom (producers) or top (predators) of the food chain impact the entire community. Additionally, they reveal how energy flows and is distributed in both land and water environments, making them crucial for ecological studies.
In simple words: Food webs are important because they show how all living things are connected, how energy moves, and how changes in one part affect the whole ecosystem.

🎯 Exam Tip: Explain that food webs illustrate the complex nature of ecosystems, unlike simple food chains, by showing multiple feeding pathways and greater stability.

 

Question 23. What are the types of carbon?
Answer: There are different types of carbon based on where they are stored and how they are used: * **Green carbon:** This is carbon stored in the biosphere, mostly by plants through photosynthesis. * **Grey carbon:** This refers to carbon stored in fossil fuels like coal, oil, and biogas deposits deep within the lithosphere (Earth's crust). * **Blue carbon:** This is carbon stored in the atmosphere and oceans, especially in coastal and marine ecosystems. * **Brown carbon:** This is carbon stored in industrialized forests, typically found in wood used for commercial articles and products. * **Black carbon:** This is carbon emitted into the atmosphere as soot from burning fossil fuels like gas, diesel, and coal, often from power plants.
In simple words: Carbon can be green (in plants), grey (in fossil fuels), blue (in air and oceans), brown (in wood products), or black (soot from burning fuels).

🎯 Exam Tip: When listing types of carbon, ensure you clearly state where each type is *stored* or *emitted* to distinguish them effectively.

 

IV. Five Marks

 

Question 1. Define ecosystem. Describe the components of ecosystem
Answer: An ecosystem, a term proposed by A.G. Tansley in 1935, is a natural system where living (biotic) and non-living (abiotic) parts interact together. Odum (1962) described it as the basic unit of ecology that has both structure and function. Ecosystems are made up of two main components:
(i) **Abiotic (non-living) components:** These include physical factors like soil, air, water, pH, sunlight, and temperature. They also include inorganic substances such as carbon, hydrogen, oxygen, nitrogen, and phosphorus, which are crucial for supporting life.
(ii) **Biotic (living) components:** These are all the living organisms, including plants, animals, fungi, and bacteria. They form the trophic (feeding) structures of any ecosystem and are divided into: * **Autotrophs:** These are producers, like plants, that make their own food using photosynthesis. They form the base of the food chain. * **Heterotrophs:** These are consumers that get their energy by eating other organisms. They are further divided into: * **Macro consumers:** Larger consumers like herbivores (plant-eaters), carnivores (meat-eaters), and omnivores (both plant and meat-eaters). * **Micro consumers:** Smaller organisms, mainly decomposers like bacteria and fungi, that break down dead organic matter. Both abiotic and biotic parts work together to create a balanced system, forming food chains, food webs, and ecological pyramids, making ecosystems complex and self-regulating.
In simple words: An ecosystem is where living and non-living things work together. Living parts are plants and animals, while non-living parts are soil, water, and air. Plants make food, animals eat them, and tiny organisms break down dead things, all keeping the system balanced.

🎯 Exam Tip: When defining an ecosystem, always mention the interaction between biotic and abiotic components. For components, clearly separate and elaborate on autotrophs, macro consumers, and micro consumers within the biotic section.

 

Question 1. Define ecosystem. Describe the components of ecosystem
Answer: The term ecosystem was first used by A.G. Tansley in 1935. He described it as a system formed by the interaction of all living and non-living parts of an environment. Odum (1962) later defined an ecosystem as the basic unit of ecology that has structure and function. An ecosystem has two main parts: biotic (living) and abiotic (non-living) components. Understanding these components helps us see how all parts of nature are connected.
i) Abiotic (non-living) components:
These include physical factors like soil, air, water, and soil pH. They also cover geographical factors like latitude and altitude, and chemical components like carbohydrates, proteins, lipids, and humic substances. Inorganic substances like carbon, hydrogen, oxygen, nitrogen, and phosphorus are also important. These non-living parts are very important for the overall health and "standing quality" of any ecosystem.
ii) Biotic (living) components:
These are all the living things in an ecosystem, such as plants, animals, fungi, and bacteria. They form the different feeding levels (trophic structures) of the ecosystem. Biotic components are divided into two types:
i) Autotrophic components: These are organisms like plants, also called producers. They make their own food using simple inorganic materials through a process called photosynthesis.
ii) Heterotrophic components: These are organisms that eat producers or other consumers. They are called consumers and are of two main types:
i) Macro consumers: These include herbivores (plant-eaters), carnivores (meat-eaters), and omnivores (eat both plants and meat).
ii) Micro consumers: These are decomposers like bacteria, actinomycetes, and fungi. They break down dead organic matter. These living parts are very important for creating food chains, food webs, and ecological pyramids.

🎯 Exam Tip: When defining an ecosystem, always mention both biotic and abiotic components and their basic roles, highlighting their interconnectedness.

 

Question 2. What kind of solar radiation is used in photosynthesis ? (OR) AR is not always constant because of clouds, tree shades, air, dust particles, seasons latitudes and length of the daylight availability. (OR) What is photosynthetically active radiation ? (OR) How it is calculated for active photosynthesis in plants ? (OR) From the sunlight, only 2-10% of the solar energy is used by green plants for photosynthesis. Explain why?
Answer: Photosynthetically Active Radiation (PAR) is the specific light energy that plants use for photosynthesis. It is the amount of light available to plants for this process. PAR falls within the wavelength range of 400-700 nm. Green plants primarily absorb blue and red light for efficient photosynthesis. From all the sunlight that reaches Earth, only about 34% gets to the atmosphere, 10% is held by ozone, and 56% reaches the Earth's surface. Out of this surface radiation, only a small amount, 2-10%, is actually used by green plants for photosynthesis; the rest is lost as heat. This process helps convert light into chemical energy, which is essential for life.
PAR is measured in millimoles per square meter per second, typically using silicon photovoltic detectors. At night, PAR is zero because there is no sunlight. During the middle of summer days, PAR can be very high, often reaching 2000-3000 millimoles per square meter per second.

🎯 Exam Tip: Focus on the specific wavelength range (400-700 nm) for PAR and remember the low efficiency (2-10%) of solar energy conversion by plants in photosynthesis. Also, clarify that PAR is not always constant due to various environmental factors.

 

Question 3. What is primary productivity ? What are its types ? What are the factors affecting primary productivity ? (or) How net primary productivity is calculated ? What are the factors affecting primary productivity.
Answer: Primary productivity is the total amount of chemical energy or organic matter made by autotrophs (like plants) through photosynthesis and chemosynthesis. It is the first source of energy for all living things, from bacteria to humans.
There are two main types of primary productivity:
a. Gross Primary Productivity (GPP): This is the total amount of food energy or biomass produced by autotrophs in an ecosystem during photosynthesis. It represents all the energy captured.
b. Net Primary Productivity (NPP): This is the amount of energy left after plants use some of the GPP for their own respiration. It is the energy available for other organisms in the ecosystem. NPP is calculated as: NPP = GPP - Respiration. The Earth's biosphere is estimated to have a total NPP of about 170 billion tons of dry weight per year. Out of this, oceanic producers contribute around 55 billion tons per year.
Factors that affect primary productivity are:
- The specific plant types in an area.
- How well plants can photosynthesize.
- The amount of nutrients available.
- How much sunlight is received.
- The amount of rainfall.
- The type of soil.
- The topography (shape of the land).
- Other environmental factors. These factors show how complex it is for plants to produce energy in different environments.

🎯 Exam Tip: Clearly define GPP and NPP, providing the formula for NPP. Remember to list multiple factors that influence primary productivity, as this demonstrates a complete understanding.

 

Question 4. What is secondary productivity and its types ? In what way community productivity calculated ?
Answer: Secondary productivity refers to the amount of energy stored in the tissues of heterotrophs, also known as consumers. This energy is not created from scratch but is obtained by eating other organisms.
There are two main types of secondary productivity:
a. Gross Secondary Productivity: This is the total amount of plant material consumed by herbivores, minus any materials they cannot digest and lose as waste (faeces).
b. Net Secondary Productivity: This is the energy or biomass stored by consumers in a specific area over a period, after they have used some energy for their own respiration. It represents the energy available for the next trophic level.
Community productivity: This measures the rate at which organic matter (biomass) is made by all the plants in a community over a certain time and area. It shows the overall health and activity of the entire plant community.

🎯 Exam Tip: Distinguish between gross and net secondary productivity. Remember that secondary productivity always involves consumers, unlike primary productivity which involves producers.

 

Question 5. How does energy flow in an ecosystem, (or) Describe about the concept of trophic level in an ecosystem, (or) Write about various trophic level of food chain in an ecosystem.
Answer: Energy flow in an ecosystem describes how energy moves from one living thing to another. A trophic level is a position an organism holds in a food chain, showing where it gets its energy. The number of trophic levels depends on how many steps there are in the food chain.
- Green plants, called producers, are at the first trophic level (T1). They make their own food.
- Plant-eaters, called herbivores or primary consumers, are at the second trophic level (T2). They eat producers.
- Carnivores that eat herbivores are at the third trophic level (T3). They are called secondary consumers.
- Carnivores that eat other carnivores are at the fourth trophic level (T4). They are called tertiary consumers.
- Some organisms, like crows, are omnivores because they eat both plants and animals. They can be at more than one trophic level in the food chain. This flow ensures that energy is transferred throughout the ecosystem, supporting all life forms.

🎯 Exam Tip: Clearly define trophic levels and explain how different organisms (producers, consumers, omnivores) fit into these levels, demonstrating the directional flow of energy.

 

Question 6. How does the laws of thermodynamics explain the storage and loss of energy in an ecosystem ? (or) Write about laws of thermodynamics in an ecosystem.
Answer: The way energy is stored and lost in an ecosystem follows two basic laws of thermodynamics.
i) First law of thermodynamics:
This law states that energy cannot be created or destroyed; it can only change from one form to another. So, the total amount of energy in the universe stays constant. For example, during photosynthesis, plants convert light energy into chemical energy (starch). No energy is lost or gained during this conversion; it simply changes its form. This means the overall energy budget of an ecosystem is conserved.
\[ 6CO_2 + 6H_2O \xrightarrow{\text{Light, Chlorophyll}} C_6H_{12}O_6 + O_2 \]

\( \implies \) Light energy \( \rightarrow \) Chemical energy
ii) Second law of thermodynamics:
This law states that during any energy transfer, some energy is always lost as heat. Energy transformations are never 100% efficient. When energy moves from one organism to another in a food chain, only about 10% is stored in the new organism's tissues. The remaining 90% is lost as heat through processes like respiration and decomposition. This is known as the "Ten Percent Law," explaining why food chains usually have only a few trophic levels and why the amount of energy decreases at higher levels. This constant loss of energy as heat means that ecosystems need a continuous input of energy, mainly from the sun.

🎯 Exam Tip: Clearly explain both laws and connect them directly to energy flow in ecosystems. For the second law, mention the "Ten Percent Law" as a key concept.

 

Question 7. What is food chain ? (or) How does movement takes place from producers to top carnivore? What are its types.
Answer: A food chain shows how energy moves from one living thing to another in an ecosystem. It describes who eats whom, starting from producers and going up to top carnivores. There are two main types of food chains:
1. Grazing food chain: This food chain gets its energy from the sun. It starts with producers (plants). For example, a mouse eats plants (primary consumers), then a snake eats the mouse (secondary consumer), and finally, an eagle eats the snake (tertiary consumer). The sun is the main source of energy that kicks off this chain.
2. Detritus food chain: This food chain starts with dead organic matter, which is a big source of energy. This dead matter comes from dead plants, animals, and their waste. Organisms called detritivores (like earthworms) eat this dead matter. Then, small carnivores eat the detritivores, and large carnivores eat the small carnivores. This type of food chain is found in all ecosystems, showing how nutrients are recycled. The transfer of energy through dead organic matter ensures that even decomposed materials contribute to the energy flow.

🎯 Exam Tip: Differentiate between grazing and detritus food chains by their starting points (sunlight vs. dead organic matter) and give clear examples for each.

 

Question 8. What is ecological pyramid ? Write about ecological pyramid of number.
Answer: An ecological pyramid is a drawing that shows the trophic structure and how it works at different feeding levels in an ecosystem. These are also called Eltonian pyramids. Ecological pyramids help us understand the relationships between different groups of organisms. There are different types of ecological pyramids, including pyramids of number, biomass, and energy.
Pyramid of number:
This pyramid shows the number of individual organisms at each trophic level. The shape of these pyramids can vary:
- In grassland and pond ecosystems, the pyramid of number is usually upright. This means there are many producers at the bottom, and the number of organisms decreases at each higher level.
- In a forest ecosystem, the pyramid of number is spindle-shaped. There are fewer large trees (producers) at the base, more herbivores (like birds and insects) in the middle, and then fewer secondary and tertiary consumers. For instance, a single large tree can support many insects.
- In a parasite ecosystem, the pyramid of number is inverted. This happens because one large host organism (like a tree) can support many smaller parasites, and those parasites can, in turn, support even smaller hyper-parasites. This shows an increase in the number of organisms as you move up the trophic levels from the producers.

🎯 Exam Tip: When explaining ecological pyramids, be sure to describe the shape for different ecosystems (upright, spindle, inverted) and relate it back to the number of organisms at each trophic level.

 

Question 9. Write about the mechanism of decomposition ? What are the factors affecting decomposition, (or) Describe about an essential process for recycling and balancing the nutrient pool in an ecosystem.
Answer: Decomposition is a process where dead organic matter is broken down into simpler substances. It is a very important part of recycling nutrients in an ecosystem. This process happens in several steps:
- Fragmentation: Detritivores, like bacteria, fungi, and earthworms, break down large pieces of dead organic material (detritus) into smaller particles. This is the first step in making the material easier to decompose.
- Catabolism: Decomposers release special chemicals (extracellular enzymes) into their surroundings. These enzymes break down complex organic and inorganic compounds into simpler forms. This step releases nutrients locked in the detritus.
- Leaching or Eluviation: Water-soluble organic and inorganic compounds from the surface move down to lower layers of the soil with water. This process helps distribute nutrients deeper into the soil.
- Humification: During this stage, simplified detritus changes into a dark-colored, amorphous substance called humus. Humus is very resistant to microbial action, meaning it breaks down very slowly. Humus helps the soil retain water and nutrients.
- Mineralization: This is the final step where inorganic nutrients are released from the humus. Various microbes are involved in releasing these essential nutrients back into the ecosystem, making them available for plants again. This entire process is crucial for maintaining the balance of nutrients in nature.

🎯 Exam Tip: Remember the five distinct steps of decomposition (fragmentation, catabolism, leaching, humification, mineralization) and the role of detritivores and microbes in each step.

 

Question 10. Define pyramid of biomass. What are its types based on shape ?
Answer: A pyramid of biomass is a drawing that shows the total amount of organic material (biomass) present at each feeding level (trophic level) in an ecosystem. It helps us see how biomass changes as we move up the food chain.
Based on its shape, there are two main types:
- Upright Pyramid: In grasslands and forest ecosystems, the pyramid of biomass is upright. This means there is a large amount of biomass at the producer level (like grass or trees), and the amount of biomass gradually decreases at each higher trophic level (herbivores, carnivores). For example, many plants support fewer deer, which support even fewer lions.
- Inverted Pyramid: In a pond ecosystem, the pyramid of biomass is inverted. This means the producers (like phytoplankton) have very little biomass at any given time. However, they reproduce quickly and are eaten by primary consumers (like zooplankton), which have more biomass. The biomass then increases at higher trophic levels towards the top carnivores. The smaller, faster-reproducing producers support a larger biomass of consumers above them. These different shapes show how ecosystems can vary in their biomass distribution.

🎯 Exam Tip: Explain both upright and inverted pyramid shapes for biomass, and give specific examples (grassland/forest for upright, pond for inverted) to illustrate the concept.

 

Question 11. Write about the structure of pond ecosystem with diagram.
Answer: A pond ecosystem is a natural, self-sustaining freshwater ecosystem. It has both living (biotic) and non-living (abiotic) parts that work together. The various components include:
- Abiotic components: These are the non-living parts like dissolved gases (carbon dioxide, oxygen), inorganic substances (calcium, nitrogen, phosphorus), and organic substances (amino acids, humic acid) that come from dead organic matter. Factors like light, temperature, and water pH also affect how the pond functions. These physical and chemical elements are essential for supporting life in the pond.
- Biotic components: These are the living organisms in the pond, grouped into producers, consumers, and decomposers.
- Producers: These make their own food. In a pond, they include various phytoplankton (like Oscillatoria, Anabaena, Eudorina, Volvox, Diatoms), filamentous algae, and rooted or floating plants.
- Consumers: These eat other organisms. They include zooplankton, benthos (bottom-dwelling organisms), secondary consumers (like water beetles and frogs), and tertiary consumers (like large fish, hawks, and humans).
- Decomposers: These break down dead organic matter. They are microorganisms like bacteria and fungi. They help recycle nutrients back into the pond.
The diagram shows how these parts interact, with energy flowing from producers to consumers, and nutrients being recycled by decomposers.

🎯 Exam Tip: When describing the structure of a pond ecosystem, make sure to detail both abiotic and biotic components with specific examples for each category. The diagram helps illustrate these connections.

 

Question 12. Write important features of a sedimentation cycle in an ecosystem.
Answer: Sedimentation cycles are very slow processes where nutrients move through the Earth's crust (lithosphere) and hydrosphere (water bodies). These cycles take a long time to complete because nutrient elements often get trapped in sediment rocks for extended periods, making them unavailable for use. Phosphorus, sulfur, and calcium are examples of nutrients that primarily cycle through sedimentation.
Key features of sedimentation cycles include:
- They are a type of sedimentary cycle, meaning nutrients are stored in sediments on Earth.
- Phosphorus, an important element, is found in biomolecules like DNA, RNA, ATP, NADP, and phospholipids in living organisms.
- Large amounts of phosphorus are present in rock deposits, marine sediments, and guano (bird and bat droppings).
- Phosphorus is released from these deposits through weathering, such as rain and wind breaking down rocks.
- Producers (plants) absorb phosphorus as phosphate ions. This phosphorus then moves through the food chain as organisms eat each other.
- When organisms die, decomposers break them down. This process releases phosphorus back into the lithosphere and hydrosphere, ensuring the phosphorus cycle continues. These cycles highlight the long-term movement of critical nutrients through geological processes.

🎯 Exam Tip: Highlight that sedimentation cycles are slow and involve storage in Earth's crust. Emphasize phosphorus as a key example and its movement through living organisms and geological deposits.

 

Question 13. Based on the varieties of benefits obtained from ecosystem what are the various types ecosystem services ?
Answer: Ecosystem services are the many benefits that nature provides to people. These benefits are generally grouped into four main types:
- Provisioning Services: These are the products we get from ecosystems. Examples include food (like crops and fish), fresh water, timber, fuel, natural fibers, and medicinal plants. These services directly support human life.
- Cultural Services: These are the non-material benefits that enrich human lives. They include spiritual and religious values, opportunities for recreation and tourism, educational benefits, and aesthetic enjoyment from natural landscapes. These services contribute to our well-being and sense of place.
- Supporting Services: These are the basic natural processes that are necessary for all other ecosystem services to exist. They include nutrient cycling (like the carbon and nitrogen cycles), soil formation, primary production (plants making food), and habitat provision for wildlife. These services work behind the scenes to maintain the ecosystem.
- Regulating Services: These are the benefits we get from the way ecosystems control natural processes. Examples include climate regulation (absorbing carbon dioxide), pest and disease control, flood and erosion control, water purification, and pollination of crops. These services help keep our environment stable and safe.
These four types of services show how much we rely on healthy ecosystems for our survival and quality of life.

🎯 Exam Tip: Memorize the four main categories of ecosystem services (provisioning, cultural, supporting, regulating) and be ready to provide 2-3 specific examples for each category.

 

Question 14. Discuss about the various benefits of mangrove ecosystem services, (or) What are the various benefits of mangrove ecosystem services to nature and human being?
Answer: Mangrove ecosystems provide many valuable benefits to nature and people. These special coastal forests are very important for the environment:
- Mangroves offer essential habitats and act as nurseries for many aquatic plants and animals. They provide a safe place for young fish, crabs, and other creatures to grow. They also provide humans with resources like medicine, fuelwood, and timber.
- They serve as a natural bridge between land and sea, helping to balance the buildup of sediment and prevent soil erosion along coastlines.
- Mangroves help reduce the force of water during extreme weather events like cyclones and tsunamis, protecting inland areas from severe damage.
- They produce oxygen, absorb carbon dioxide from the atmosphere (carbon sequestration), and prevent saltwater from spraying onto freshwater areas, which protects land plants. These unique trees are critical for coastal health and human well-being.

🎯 Exam Tip: Focus on the specific roles of mangroves in coastal protection, biodiversity support, and carbon sequestration. Emphasize their dual benefits to both nature and human communities.

 

Question 15. If we fail to protect environment, we will fail to save posterity? (or) What are the practices we have to follow to protect the ecosystem ? (or) How to protect the ecosystem ?
Answer: To protect our ecosystem and ensure a healthy future for everyone, we must adopt several practices in our daily lives:
- Only buy and use products that are eco-friendly, and make sure to recycle them. This reduces waste and the demand for new resources.
- Plant more trees to increase green cover, which helps improve air quality and supports biodiversity.
- Choose farm products (like vegetables, fruits, and greens) that are grown sustainably. This reduces the use of harmful chemicals and saves natural resources.
- Always recycle waste and aim to produce less waste overall. This lessens the burden on landfills and prevents pollution.
- Reduce your consumption of water and electricity. Turning off lights and taps when not in use saves valuable resources.
- Limit or stop using household chemicals and pesticides that can harm the environment.
- Keep your cars and vehicles well-maintained to reduce carbon emissions, which helps combat air pollution.
- Spread awareness and educate your friends and family about protecting ecosystems. Encourage them to find solutions for environmental problems. These small actions collectively make a big difference for our planet.

🎯 Exam Tip: For questions on environmental protection, list practical, actionable steps that individuals can take. Group your points logically (e.g., consumption, waste, awareness) to ensure a comprehensive answer.

 

Question 16. What are the strategy of ecosystem management?
Answer: Ecosystem management involves several key strategies:

• It helps in preserving the variety of life, also known as biodiversity, within ecosystems.
• It points out when an ecosystem is damaged. For example, some species, called flagship species, act as indicators of the ecosystem's health.
• It helps to understand and plan for changes in the ecosystem that are hard to avoid.
• This management is a tool used to make sure ecosystems are used in a way that can be maintained over a long time, helping achieve sustainability goals.

In simple words: Ecosystem management helps us protect the different kinds of plants and animals, see when an ecosystem is hurt, plan for future changes, and keep nature healthy for a long time. It helps us protect our natural world.

🎯 Exam Tip: When listing strategies for ecosystem management, remember to cover aspects like biodiversity, health indicators, planning for change, and sustainability to score full marks.

 

Question 17. What are various steps involved in ecological succession? (or) What are the characteristics of ecological succession?
Answer: The main features of ecological succession are:

• It is an organized process that changes how plant communities are structured.
• These changes happen because of shifts in both non-living (abiotic) and living (biotic) factors.
• It transforms an unstable community into one that is stable over time.
• Over time, there's a slow increase in the variety of species, the total amount of living matter, how specialized different living spaces (niches) become, and the amount of rich organic matter (humus) in the soil.
• The process moves from simple food chains to more complex food webs.
• It changes simpler and lower life forms into more complex and higher life forms.
• It creates a system where plants and animals depend on each other for survival.

In simple words: Ecological succession is a step-by-step change in nature where simple plant and animal groups slowly get replaced by more complex ones. It makes the environment more stable and diverse over time, building a balanced community.

🎯 Exam Tip: When describing ecological succession, focus on it being a gradual, directional process leading to a stable climax community, and mention the roles of both living and non-living factors.

 

Question 18. Tabulate the differences between primary and secondary succession?
Answer: Here are the differences between primary and secondary succession:

In simple words: Primary succession starts from scratch, like on new rock, and takes a very long time. Secondary succession happens in an area where life once was, but got disturbed (like after a fire), so it starts faster because soil is already there.

🎯 Exam Tip: Remember that the key difference is the starting condition: primary succession begins with no soil, while secondary succession begins in an area where soil and some life forms already exist after a disturbance.

 

Question 19. Write about the different stages of hydrosere? (or) Write about the different substages of hydrosere in plant succession.
Answer: Hydrosere is a type of ecological succession that starts in a water environment, like a pond or lake, and slowly leads to a land-based community. It goes through several stages:

(1) **Phytoplankton Stage:** This is the very first stage where tiny floating plants (phytoplankton) like blue-green algae, green algae, diatoms, and bacteria appear. When these organisms live and die, they add organic matter and nutrients to the pond, preparing it for the next stages.

(2) **Submerged Plant Stage:** As the tiny planktons die and decompose, and as silt from rainwater settles, a loose layer of mud forms at the bottom of the pond. This new bed allows rooted plants that grow completely underwater, called submerged hydrophytes (like Chara and Utricularia), to start growing. Their growth and decay make the pond shallower.

(3) **Submerged Free-Floating Stage:** At this point, the pond's depth is about 2-5 feet. Now, plants that are rooted but have large leaves floating on the surface (like Nelumbo, Nymphaea) and other free-floating plants (like Azolla and Pistia) begin to grow. Their death and decomposition continue to make the pond even shallower.

(4) **Reed-Swamp Stage (Amphibious Stage):** This stage is called "amphibious" because plants here can live both in water and in air. Rooted floating plants are replaced by taller plants like Typha, Phragmites, and Sagittaria. By the end of this stage, the water level becomes very low, making it difficult for amphibious plants to grow further.

(5) **Marsh Meadow Stage:** As the water level keeps dropping, the pond eventually turns into a marshy meadow. Plants like Cyperaceae and Poaceae (grasses) colonize the area, forming a dense, mat-like growth with their root systems. These plants absorb a lot of water and help dry out the area, causing the marshy plants to disappear and leading to the growth of shrubs.

(6) **Shrub Stage:** Terrestrial plants, such as shrubs (like Salix and Cornus) and small trees (like Populus and Alnus), start to invade these drier areas. These plants absorb even more water, making the habitat drier. Also, the breakdown of dead plants and animals creates a rich humus layer in the soil, which helps new tree species arrive and grow.

(7) **Forest Stage:** This is the final and most stable community in a hydrosere, also known as the climax community. Various types of trees grow here, forming diverse forests. Examples include temperate mixed forests (like those with Ulmus, Acer, Quercus) or tropical rainforests (with Artocarpus, Cinnamomum, Bamboo, Tectona). This stage represents a fully developed terrestrial ecosystem.

In simple words: Hydrosere is how a watery place slowly turns into a forest. It starts with tiny plants in water, then plants that live partly in water, then marshy grasses, then bushes, and finally big trees grow as the water disappears and the land becomes dry. Each step changes the environment for the next group of plants.

🎯 Exam Tip: Remember the sequence of stages in hydrosere: Phytoplankton → Submerged → Floating → Reed-swamp → Marsh Meadow → Shrub → Forest. Understanding how each stage makes the environment less watery is key.

 

Question 20. Write about the significance of plant succession.
Answer: Plant succession is very important for understanding how ecosystems change and develop. Here's why it's significant:

• Succession is a dynamic process, meaning it's always changing. Ecologists can study these stages to understand how plant communities grow in a specific area.
• Knowing about ecological succession helps us manage forests better, allowing us to control the growth of certain plant species.
• This knowledge can even be used to protect dams by understanding how siltation (buildup of mud) occurs and how to prevent it.
• It provides information on effective techniques for planting new forests (reforestation) and growing trees in open areas (afforestation).
• It helps in keeping pastures healthy and productive for grazing animals.
• Plant succession is crucial for maintaining the diversity of species within an ecosystem.
• The patterns of how species diversity changes during succession are affected by how much resources are available and how often disturbances (like fires or floods) happen.

In simple words: Plant succession is important because it explains how nature slowly changes, allowing different plants to grow and replace each other over time. This process helps create diverse, stable environments, keeps them healthy, and helps us manage natural resources better.

🎯 Exam Tip: Highlight that plant succession is not just about plant changes but also impacts biodiversity, ecosystem stability, and human management strategies for natural resources.

 

Question 21. What is carbon cycle? Draw the diagrammatic sketch showing carbon cycle?
Answer: The carbon cycle is the process by which carbon atoms are continuously exchanged among the Earth's atmosphere, oceans, land, and living organisms. It's a natural biogeochemical cycle that helps regulate the Earth's climate and provides carbon for all life forms. This continuous movement of carbon helps maintain the balance of the planet.
The diagrammatic representation shows the process of decomposition and cycling of nutrients. Here's a description of the carbon cycle as illustrated in the diagram (which conceptually depicts the decomposition process that is part of the carbon cycle):
The cycle begins with **Raw material for decomposition**, such as dead plants and animals. This material undergoes a process called **Senescence**, which refers to the aging and dying of plant tissues.
Next, **Fragmentation** occurs, where detritivores (like bacteria, fungi, and earthworms) break down the dead organic matter into smaller pieces.
Simultaneously, **Leaching** happens, where water-soluble inorganic nutrients seep into the soil from the fragmented detritus.
**Catabolism** involves decomposers releasing extracellular enzymes that further break down complex organic and inorganic compounds into simpler ones.
Finally, **Humification** transforms the simplified detritus into a dark, amorphous substance called humus, which is resistant to microbial action.
From these processes, **Mineralisation** occurs, releasing inorganic nutrients back into the soil, completing the cycle and making nutrients available for **Absorption by plants** again.

In simple words: The carbon cycle is how carbon moves around the Earth between the air, land, oceans, and living things. Plants take carbon from the air, animals eat plants, and when living things die, carbon goes back into the soil and air. This keeps carbon available for all life.

🎯 Exam Tip: For the carbon cycle, remember the main reservoirs (atmosphere, oceans, land) and key processes (photosynthesis, respiration, decomposition, combustion) that move carbon between them. When drawing, simplify the flow to show these connections.