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Detailed Chapter 7 Energy Flow in an Ecosystem MSBSHSE Solutions for Class 9 Science
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Class 9 Science Chapter 7 Energy Flow in an Ecosystem MSBSHSE Solutions PDF
Std 9 Science Chapter 7 Energy Flow In An Ecosystem Question Answer Maharashtra Board
Question 1. Complete the following table (Carefully study the carbon, oxygen and nitrogen cycles).
| Bio-geo-chemical cycles | Biotic processes | Abiotic processes |
|---|---|---|
| 1. Carbon cycle | ||
| 2. Oxygen cycle | ||
| 3. Nitrogen cycle |
Question 2. Correct and rewrite the following statements and justify your corrections.
a. Carnivores occupy the second trophic level in the food chain.
b. The flow of nutrients in an ecosystem is considered to be a 'one-way' transport.
c. Plants in an ecosystem are called primary consumers.
Question 3. Give reasons.
a. Energy flow through an ecosystem is 'one way'.
Answer:
- The Sun is the most important source of energy in any ecosystem.
- Green plants of the ecosystem store some amount of solar energy in the form of food.
- Before reaching the decomposers, this energy is passed on from one trophic level to the next.
- Decomposers dissipate some amount of energy in the form of heat.
- However, no part of the energy ever returns to the Sun. Hence, energy flow through an ecosystem is 'one way'.
In simple words: Energy flows in one direction from the Sun to plants, then to consumers, and finally to decomposers, with some energy lost as heat at each step, never returning to the Sun.
🎯 Exam Tip: Focus on the unidirectional nature of energy flow and how energy is transformed and lost at each trophic level, emphasizing the Sun as the ultimate source.
b. Equilibrium is necessary in the various bio-geo-chemical cycles.
Answer:
- The cyclic flow of nutrients within an ecosystem is called bio-geo-chemical cycles.
- Nutrients, necessary for the growth of organisms are continuously transferred from abiotic to biotic factors and biotic to abiotic factors within an ecosystem.
- Any imbalance in the cycles will break the link between the biotic and abiotic factors.
- Therefore, equilibrium is necessary between bio-geo-chemical cycles.
In simple words: Bio-geo-chemical cycles continuously move essential nutrients between living and non-living components. Maintaining a balance in these cycles is crucial because any disruption would break the vital connections between these factors, impacting the entire ecosystem.
🎯 Exam Tip: Highlight the continuous transfer of nutrients and how equilibrium ensures the integrity of the ecosystem's biotic and abiotic links.
c. Flow of nutrients through an ecosystem is cyclic.
Answer:
- All organisms need nutrients for their growth.
- The nutrients carbon, oxygen, nitrogen, iron, calcium etc. are circulated and recycled from the biosphere to living organisms and after their death back to the biosphere.
- Nutrients are taken up by plants and then passed on to the consumers.
- Eventually, after their death, all types of consumers, are decomposed by decomposers like bacteria and fungi and the nutrients are again released into the biosphere and are, used again by living organisms.
In simple words: Nutrients vital for life, like carbon and nitrogen, are continuously taken up by plants, consumed by animals, and then returned to the environment by decomposers after death, ensuring a cyclic replenishment within the ecosystem.
🎯 Exam Tip: Explain the path of nutrient cycling, from uptake by producers to return by decomposers, to illustrate its continuous, cyclical nature.
Question 4. Explain the following cycles in your own words with suitable diagrams.
a. Carbon cycle.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र कार्बन चक्र को दर्शाता है, जिसमें कार्बन डाइऑक्साइड वातावरण से पौधों द्वारा प्रकाश संश्लेषण के माध्यम से ली जाती है। पौधे और जानवर दोनों श्वसन के माध्यम से कार्बन डाइऑक्साइड छोड़ते हैं। जैविक अपघटन और जीवाश्म ईंधन के जलने से भी कार्बन डाइऑक्साइड वातावरण में वापस आती है, जबकि जल में भी कार्बन का अवशोषण होता है।
Answer:
- The circulation and recycling of carbon from the atmosphere to living organisms and after their death back to the atmosphere is called the carbon cycle.
- Abiotic carbon atoms are circulated and recycled into biotic form mainly through photosynthesis and respiration.
- Hence, the carbon cycle is one of the important bio-geochemical cycles.
- Plants convert carbon dioxide into carbohydrates by the process of photosynthesis.
- Similarly, they produce carbon compounds like proteins and fats, too.
- Carnivores feed upon herbivores. In this way, biotic carbon is transported from plants to herbivores, from herbivores to carnivores and from carnivores to apex consumers.
- Main processes in the carbon cycle
\[6 CO_{2} + 12 H_{2}O \xrightarrow{\text{Sunlight, Chlorophyll}} C_{6}H_{12}O_{6} + 6 H_{2}O + 6 O_{2} \uparrow\]
\[C_{6}H_{12}O_{6} + 6 O_{2} \xrightarrow{\text{Mitochondria}} 6 CO_{2} \uparrow + 6 H_{2}O + \text{Energy}\] - Eventually, after death, all types of consumers, are decomposed by decomposers like bacteria and fungi and carbon dioxide is released again into the atmosphere and is used again by living organisms.
- In this way, carbon is continuously passed on from one living organism to another. After the death of living organisms, carbon goes to the atmosphere and is again taken up by living organisms.
In simple words: The carbon cycle is the continuous movement of carbon between the atmosphere, living organisms, and the Earth. Plants absorb carbon dioxide for food, which then moves through the food chain and is released back into the atmosphere through respiration, decomposition, and burning fossil fuels.
🎯 Exam Tip: Remember the two main processes: photosynthesis (carbon uptake by plants) and respiration (carbon release by organisms). Also, understand the role of decomposers and fossil fuels in the cycle.
b. Nitrogen cycle.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र नाइट्रोजन चक्र को दर्शाता है, जिसमें गैसीय नाइट्रोजन (N2) को नाइट्रोजन स्थिरीकरण (नाइट्रेट्स और नाइट्राइट्स का निर्माण) के माध्यम से मिट्टी में परिवर्तित किया जाता है। फिर अमोनियाकरण (अमोनिया का मोचन) और नाइट्रीकरण (अमोनिया से नाइट्राइट फिर नाइट्रेट) की प्रक्रियाएँ होती हैं। अंत में, विनाइट्रीकरण (नाइट्रोजन यौगिकों का गैसीय नाइट्रोजन में रूपांतरण) द्वारा नाइट्रोजन वातावरण में वापस आ जाती है।
Answer:
- Nitrogen forms 78% i.e. the maximum portion of the atmosphere. It is necessary for the maintenance of the cycle of nature.
- The circulation and recycling of nitrogen gas into the form of different compounds through various biotic and abiotic processes in nature is called the nitrogen cycle.
- All organisms participate in the nitrogen cycle. It is an important component of proteins and nucleic acids.
- As compared to other elements, it is inactive and does not easily combine with other elements. Most organisms cannot use the free form of nitrogen.
- Important processes of nitrogen cycle:
(a) Nitrogen fixation: Conversion of nitrogen into nitrates and nitrites through atmosphere, industrial and biological processes.
(b) Ammonification: Release of ammonia through the decomposition of dead bodies and excretory wastes of organisms.
(c) Nitrification: Conversion of ammonia into a nitrite and then nitrate.
(d) Denitrification: Conversion of nitrogen compounds into gaseous nitrogen.
In simple words: The nitrogen cycle involves converting atmospheric nitrogen into usable forms like nitrates and nitrites through processes such as nitrogen fixation, nitrification, ammonification, and denitrification. This cycle is crucial as nitrogen is a key component of proteins and nucleic acids, continuously circulating between the atmosphere and living organisms.
🎯 Exam Tip: Focus on the four main processes (fixation, ammonification, nitrification, denitrification) and the role of bacteria in converting nitrogen into different forms that plants and animals can use.
c. Oxygen cycle.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र ऑक्सीजन चक्र को दर्शाता है, जिसमें पौधे प्रकाश संश्लेषण द्वारा ऑक्सीजन उत्पन्न करते हैं। जानवर ऑक्सीजन में सांस लेते हैं और कार्बन डाइऑक्साइड छोड़ते हैं। पौधे कार्बन डाइऑक्साइड को अवशोषित करते हैं और खाद्य सामग्री का उत्पादन करते हैं, इस प्रकार ऑक्सीजन और कार्बन डाइऑक्साइड के बीच संतुलन बनाए रखते हैं।
Answer:
- Oxygen forms 21% of the atmosphere. It is also present in the hydrosphere and lithosphere.
- The circulation and recycling of oxygen within the biosphere is called the oxygen cycle.
- This cycle, includes both the biotic and abiotic components. Oxygen is continuously produced as well as used up in the atmosphere.
- Oxygen is highly reactive and it readily reacts with other elements and compounds.
- As oxygen is found in various forms like molecular oxygen (O2), water (H2O), carbon dioxide (CO2), inorganic compounds etc, the oxygen cycle of the biosphere is extremely complex.
- Oxygen is released in the process of photosynthesis, whereas it is used up in processes like respiration, combustion, decomposition, corrosion, rusting, etc.
In simple words: The oxygen cycle describes the continuous movement of oxygen throughout Earth's atmosphere, hydrosphere, and lithosphere. It's primarily driven by photosynthesis, which releases oxygen, and processes like respiration, combustion, and decomposition, which consume it.
🎯 Exam Tip: Emphasize photosynthesis as the primary source of atmospheric oxygen and respiration as a major consumer, highlighting the reactive nature of oxygen and its various forms in the environment.
Question 5. What would you do to help maintain the equilibrium in the various bio-geochemical cycles? Explain in brief.
Answer:
- Bio-geo-chemical cycles always involve the achievement of equilibrium, i.e., a balance in the cycling of the nutrients between the spheres.
- Human activities that are known to be environmentally unfriendly can disrupt this balance.
- We should avoid deforestation as trees play an important role in maintaining the balance.
- We should avoid overuse of fertilizers. The fertilizers get washed away in the nearby water bodies disrupting the balance.
- Avoid burning of fossil fuels as these fuels release a large amount of carbon in the form of carbon dioxide, thus disrupting the balance.
- Vehicular emissions is another contributor to the disruption in balance of the various cycles.
- These emissions release oxides of nitrogen and carbon and other hazardous air pollutants.
- So, we must use better quality fuel like CNG or ethanol to reduce vehicular emissions.
In simple words: To maintain balance in bio-geochemical cycles, we should prevent deforestation, avoid excessive fertilizer use, reduce fossil fuel burning and vehicular emissions, and promote cleaner energy to minimize disruption from human activities.
🎯 Exam Tip: Focus on human activities that disturb these cycles and offer specific, actionable solutions to mitigate these impacts, such as reducing pollution and deforestation.
Question 6. Explain in detail the inter-relationship between the food chain and food web.
Answer:
- Interaction go on continuously between producers, consumers and decomposers.
- There is a definite sequence in these interactions which is called the food chain.
- Each chain consists of four, five or more links.
- An ecosystem consists of many food chains that are interconnected at various levels. Thus, a food web is formed.
- An organism may be the prey for many other organisms.
- For example, an insect feeds upon leaves of various plants but the same insect is the prey for different animals like frog, wall lizard, birds, etc.
- Thus, many food chains interconnected together form an intricate web called as food web.
In simple words: A food chain shows a single path of energy transfer from producers to consumers, while a food web is a complex network of interconnected food chains, showing how multiple organisms feed on and are fed upon by various other organisms in an ecosystem.
🎯 Exam Tip: Clearly define both food chain and food web. Highlight that a food web is essentially a collection of interconnected food chains, emphasizing the complexity and multiple feeding relationships in an ecosystem.
Question 7. State the different types of bio-geochemical cycles and explain the importance of those cycles.
Answer:
- The different types of bio-geo-chemical cycles are nitrogen, oxygen, carbon, water vapour, iron, calcium, phosphorus, etc.
- Nutrients, necessary for the growth of the organisms are continuously transferred from abiotic to biotic factors and biotic to abiotic factors within an ecosystem.
- These cycles operate continuously through the medium of the biosphere formed by the lithosphere, atmosphere and hydrosphere.
- (iv) The recycling of biological, geological and chemical sources of nutrients takes place through these cycles.
- Nutrients from the biosphere enter the bodies of plants and animals. Eventually, after death, all types of consumers are decomposed by decomposers like bacteria and fungi and they are again released into the biosphere and are used again by living organisms.
- Therefore, these cycles help in maintaining the flow of nutrients and energy through ecosystem and maintaining the equilibrium in the ecosystem.
In simple words: Bio-geochemical cycles like nitrogen, carbon, and oxygen cycles ensure the continuous movement and recycling of essential nutrients between living organisms and the environment (lithosphere, atmosphere, hydrosphere). These cycles are vital for sustaining life and maintaining ecological balance by ensuring nutrient availability.
🎯 Exam Tip: List key bio-geochemical cycles and focus on their dual role: continuous nutrient transfer and maintaining equilibrium within the ecosystem. The recycling aspect is crucial for sustainability.
Question 8. Explain the following with suitable examples.
a. What type of changes occur in the amount of energy during its transfer from plants to apex consumers?
Answer:
- Plants of the ecosystem store some of the solar energy in the form of food.
- Before reaching the decomposers, this energy is passed on from one trophic level to the next.
- At every trophic level, some amount of energy is used by the organism for its own life processes and some amount of energy is lost to the surroundings.
- Decomposers dissipate some amount of energy in the form of heat.
- However, no part of the energy ever returns to the Sun. Hence, such passage of energy is referred to as 'one way' transport.
- Therefore, energy is maximum at the base of the pyramid and is least at the apex, e.g.
- phytoplanktons which form the base of the pyramid have 10,000 kcal of energy while humans at the apex have 10 kcal of energy.
In simple words: During energy transfer from plants to apex consumers, the amount of energy significantly decreases at each trophic level. Organisms use energy for life processes and some is lost as heat, meaning only about 10% is passed to the next level, resulting in the least energy at the top.
🎯 Exam Tip: Focus on the 10% energy transfer rule. Clearly explain how energy decreases as it moves up the trophic levels, resulting in maximum energy at the base (producers) and minimum at the apex consumers.
b. What are the differences between flow of matter and of energy in an ecosystem? Why?
Answer:
| Flow of matter | Flow of energy |
|---|---|
| (i) It involves the circulation and recycling of nutrients in a cyclic manner within the biosphere. | (i) It involves the flow of energy from one trophic level to another in a unidirectional or non-cyclic manner. |
| (ii) There is no dissipation of matter at any level. | (ii) There is the dissipation of energy at every level. |
| (iii) Biosphere is the source of nutrients. | (iii) The Sun is the most important source of energy. |
In simple words: Matter (nutrients) flows cyclically within an ecosystem, being reused and recycled without significant loss. Energy, however, flows unidirectionally from the Sun through trophic levels, with a significant portion being dissipated as heat at each step and never returning to the source.
🎯 Exam Tip: Distinguish clearly between the 'cyclic' nature of matter flow and the 'unidirectional' nature of energy flow. Emphasize that matter is recycled, while energy is continuously lost as heat and requires a constant input (from the Sun).
Class 9 Science Chapter 7 Energy Flow In An Ecosystem Intext Questions And Answers
Can you recall?
Question 1. What is meant by nitrogen fixation?
Answer:The process of conversion of Nitrogen into nitrates and nitrites is called Nitrogen fixation.
In simple words: Nitrogen fixation is the process where atmospheric nitrogen is converted into usable nitrogen compounds like nitrates and nitrites, mainly by certain microorganisms or atmospheric processes.
🎯 Exam Tip: Define nitrogen fixation precisely and mention the key end products (nitrates and nitrites) and the source (atmospheric nitrogen).
Question 2. Which microbes bring about the process of nitrogen fixation?
Answer:Rhizobium present in the root nodules of the leguminous plant bring about the process of nitrogen fixation.
In simple words: Rhizobium bacteria, found in the root nodules of leguminous plants, are the primary microbes responsible for nitrogen fixation.
🎯 Exam Tip: Identify Rhizobium and its association with leguminous plants as the key biological players in nitrogen fixation.
Question 3. What is meant by 'ecosystem'?
Answer:An ecosystem includes all of the living things like plants, animals and other organisms in a given area, interacting with each other and also with non-living environmental factors like weather, earth, sun, soil, climate and atmosphere.
In simple words: An ecosystem is a community of living organisms interacting with each other and their non-living environment (like soil, water, and air) in a specific area.
🎯 Exam Tip: The definition should clearly include both biotic (living) and abiotic (non-living) components and their interactions within a defined area.
Question 4. Which are different types of ecosystems?
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र पारिस्थितिक तंत्रों के विभिन्न प्रकारों को दर्शाता है, जिन्हें मोटे तौर पर प्राकृतिक और मानव निर्मित/कृत्रिम पारिस्थितिक तंत्रों में विभाजित किया गया है। प्राकृतिक पारिस्थितिक तंत्रों को आगे स्थलीय (जैसे जंगल, घास के मैदान, रेगिस्तान) और जलीय (जैसे समुद्री जल, ताजा जल) में उप-विभाजित किया गया है।
Question 5. How do interactions take place between biotic and abiotic factors of an ecosystem?
Answer:
- Abiotic factors include non-living factors such as soil, water etc. and biotic factors include all living organisms.
- Both these abiotic and biotic ecosystems are connected through various bio-geo-chemical cycles.
- These connections/interactions are important for the flow of matter and flow of energy.
In simple words: Biotic (living) and abiotic (non-living) factors interact through bio-geochemical cycles, where nutrients and energy are exchanged, allowing living organisms to utilize non-living resources and influencing the physical environment.
🎯 Exam Tip: Emphasize bio-geochemical cycles as the primary mechanism for interaction, facilitating the transfer of both matter and energy between living and non-living components.
Class 9 Science Chapter 7 Energy Flow in an Ecosystem Additional Important Questions and Answers
Choose and write the correct option:
Question 1. An intricate network of food chains is called
(a) Biosphere
(b) Food web
(c) Energy pyramid
(d) Ecosystem
Answer: (b) Food web
In simple words: An intricate network of food chains where multiple organisms are interconnected by feeding relationships is known as a food web.
🎯 Exam Tip: Remember that a food web represents the complex and multiple feeding pathways, distinguishing it from a single, linear food chain.
Question 2. Fungi and other microbes are called
(a) Producers
(b) Consumers
(c) Decomposers
(d) Omnivores
Answer: (c) decomposers
In simple words: Fungi and many microbes are decomposers, breaking down dead organic matter and returning nutrients to the environment.
🎯 Exam Tip: Understand the crucial role of decomposers in nutrient recycling within an ecosystem.
Question 3. Oxygen forms of the atmosphere.
(a) 78%
(b) 21%
(c) 10%
(d) 90%
Answer: (b) 21%
In simple words: Oxygen constitutes approximately 21% of the Earth's atmosphere.
🎯 Exam Tip: Recall the major gases in the atmosphere and their respective percentages, especially for oxygen and nitrogen.
Question 4. Microbes which do not need oxygen are called
(a) Producers
(b) Aerobes
(c) Anaerobes
(d) Decomposers
Answer: (c) anaerobes
In simple words: Microbes that can survive and grow in the absence of oxygen are termed anaerobes.
🎯 Exam Tip: Distinguish between aerobic (requiring oxygen) and anaerobic (not requiring oxygen) organisms based on their oxygen needs.
Question 5. The pattern of energy exchange in an ecosystem is called a
(a) Food chain
(b) Food web
(c) Pyramid of energy
(d) Trophic levels
Answer: (c) Pyramid of energy
In simple words: The pattern illustrating how energy is transferred and decreases across different trophic levels in an ecosystem is called a pyramid of energy.
🎯 Exam Tip: A pyramid of energy visually represents the quantitative decline of energy as it moves up through an ecosystem's trophic levels.
Question 6. Carbon atoms are circulated and recycled through
(a) Nitrification and denitrification
(b) Photosynthesis and respiration
(c) Respiration and nitrification
(d) Photosynthesis and ammonification
Answer: (b) photosynthesis and respiration
In simple words: Carbon atoms primarily circulate through photosynthesis (uptake by plants) and respiration (release by organisms) within an ecosystem.
🎯 Exam Tip: Identify photosynthesis and respiration as the fundamental biological processes driving the carbon cycle.
Question 7. Conversion of ammonia into a nitrite and then nitrate is called
(a) Nitrogen fixation
(b) Denitrification
(c) Nitrification
(d) Ammonification
Answer: (c) nitrification
In simple words: Nitrification is the biological process where ammonia is oxidized, first to nitrites and then to nitrates, primarily by nitrifying bacteria.
🎯 Exam Tip: Understand the sequence of nitrogen transformations: ammonia -> nitrite -> nitrate, which is specifically known as nitrification.
Question 8. The conversion of nitrogen compounds into gaseous nitrogen is called
(a) Nitrogen fixation
(b) Denitrification
(c) Ammonification
(d) Nitrification
Answer: (b) denitrification
In simple words: Denitrification is the process where bacteria convert nitrates and nitrites back into gaseous nitrogen, releasing it into the atmosphere.
🎯 Exam Tip: Denitrification completes the nitrogen cycle by returning nitrogen to its atmospheric gaseous form from soil compounds.
Question 9. is an important component of proteins and nucleic acids.
(a) Carbon
(b) Nitrogen
(c) Phosphorus
(d) Oxygen
Answer: (b) Nitrogen
In simple words: Nitrogen is a crucial element that forms the building blocks of proteins and nucleic acids, which are essential for all life forms.
🎯 Exam Tip: Recall the key elements that compose organic macromolecules; nitrogen is specific to proteins and nucleic acids.
Question 10. Amount of matter and energy from the lowest level to the highest level.
(a) decreases
(b) increases
(c) remains the same
(d) multiplies
Answer: (a) decreases
In simple words: Both the amount of matter and available energy generally decrease as you move up from the lowest (producer) to the highest (apex consumer) trophic levels in an ecosystem.
🎯 Exam Tip: Emphasize the principle of ecological pyramids, where quantities (energy, biomass) typically decrease at successive trophic levels due to loss during transfer.
Question 11. is the most important source of energy in any ecosystem.
(a) The Sun
(b) The Moon
(c) Producers
(d) Decomposers
Answer: (a) The Sun
In simple words: The Sun is the ultimate and most important source of energy for nearly all ecosystems on Earth, powering photosynthesis and the entire food web.
🎯 Exam Tip: Understand that the Sun provides the initial energy input for most ecosystems, which is then captured by producers.
Question 12. Flow of energy in an ecosystem is
(a) cyclical
(b) two way transport
(c) one way transport
(d) to and fro transport
Answer: (c) one way transport
In simple words: Energy flow in an ecosystem is unidirectional, meaning it moves in one direction from producers to consumers and does not cycle back to the source.
🎯 Exam Tip: Always remember that energy flows in a single direction (unidirectionally) in an ecosystem, unlike matter which cycles.
Question 13. The Indian Institute of Ecology and Environment, Delhi, has published
(a) Invasive species in a changing Environment
(b) Encyclopaedia of Ecology and Environment
(c) Environment and Ecology Magazine
(d) Biodiversity and Disaster Management
Answer: (b) Encyclopaedia of Ecology and Environment
In simple words: The Indian Institute of Ecology and Environment in Delhi is known for publishing the "Encyclopaedia of Ecology and Environment."
🎯 Exam Tip: This is a factual recall question; associate the institution with its notable publication in the field of ecology.
Question 14. Oxygen is released in the process of
(a) Respiration
(b) Decomposition
(c) Combustion
(d) Photosynthesis
Answer: (d) photosynthesis
In simple words: Photosynthesis, carried out by plants and other producers, is the primary process that releases oxygen into the atmosphere.
🎯 Exam Tip: Identify photosynthesis as the key process responsible for oxygen production, vital for aerobic life.
Question 15. cycle is a gaseous cycle.
(a) Carbon
(b) Phosphorus
(c) Calcium
(d) Iron
Answer: (a) Carbon
In simple words: The carbon cycle is primarily a gaseous cycle because carbon, mainly as carbon dioxide, is stored in the atmosphere and readily exchanged.
🎯 Exam Tip: Differentiate between gaseous (atmospheric reservoir) and sedimentary (earth's crust reservoir) bio-geochemical cycles.
Question 16. is a sedimentary cycle.
(a) Carbon
(b) Nitrogen
(c) Oxygen
(d) Calcium
Answer: (d) Calcium
In simple words: Calcium is involved in a sedimentary cycle, meaning its main reservoir is in the Earth's crust and sediments rather than the atmosphere.
🎯 Exam Tip: Recognize that calcium, along with phosphorus, represents a sedimentary cycle due to its primary storage in solid forms on Earth.
Question 17. is a primary consumer.
(a) Elephant
(b) Frog
(c) Owl
(d) Tiger
Answer: (a) Elephant
In simple words: An elephant is a primary consumer because it feeds directly on producers, such as plants, making it a herbivore.
🎯 Exam Tip: Identify primary consumers as herbivores that feed directly on producers (plants).
Question 18. is a secondary consumer.
(a) Grasshopper
(b) Elephant
(c) Frog
(d) Human
Answer: (c) Frog
In simple words: A frog is a secondary consumer because it eats primary consumers like grasshoppers and other insects.
🎯 Exam Tip: Understanding the different trophic levels (primary, secondary, tertiary consumers) is key to analyzing food chains and food webs.
Question 19. Tiger is a/an
(a) Producer
(b) Primary consumer
(c) Apex consumer
(d) Secondary consumer
Answer: (c) apex consumer
In simple words: A tiger is an apex consumer because it is at the top of its food chain and preys on other consumers but is not typically preyed upon itself.
🎯 Exam Tip: Apex consumers are top predators in an ecosystem, playing a critical role in maintaining population balance below them.
Question 20. Carbon dioxide is released into the atmosphere through
(a) burning of fossil fuels
(b) volcanic activity
(c) respiration
(d) all of these
Answer: (d) all of these
In simple words: Carbon dioxide enters the atmosphere through natural processes like respiration and volcanic eruptions, as well as human activities like burning fossil fuels.
🎯 Exam Tip: Knowing the various sources of carbon dioxide helps in understanding the carbon cycle and its impact on the environment.
Question 21. in 1942 studied the food chain and energy flow through it
(a) Linderman
(b) Darwin
(c) Calypso
(d) Chu win lee
Answer: (a) Linderman
In simple words: Raymond Lindeman was a pioneering ecologist who studied the quantitative flow of energy through ecosystems, establishing the concept of energy flow in food chains.
🎯 Exam Tip: Associating key scientists with their contributions helps in recalling important ecological concepts and historical developments.
Question 22. After the death of apex consumers, energy becomes available to.
(a) Decomposers
(b) Producers
(c) Herbivores
(d) Carnivores
Answer: (a) Decomposers
In simple words: When any organism dies, including apex consumers, decomposers break down their organic matter, making the stored energy and nutrients available for recycling in the ecosystem.
🎯 Exam Tip: Decomposers are essential for nutrient cycling and energy transfer, connecting all trophic levels back to the environment.
Question 23. Green plants of the ecosystem store in the form of food.
(a) Solar energy
(b) Chemical energy
(c) Thermal energy
Answer: (a) Solar energy
In simple words: Green plants capture solar energy during photosynthesis and convert it into chemical energy, which is stored in the form of food (carbohydrates).
🎯 Exam Tip: Photosynthesis is the fundamental process by which solar energy enters an ecosystem, initiating energy flow through food chains.
Question 24. Plants convert carbon dioxide into by the process of photosynthesis.
(a) Carbohydrates
(b) Proteins
(c) Fats
(d) Vitamins
Answer: (a) Carbohydrates
In simple words: During photosynthesis, plants use carbon dioxide and water to produce glucose, a type of carbohydrate, as their primary food source.
🎯 Exam Tip: Remembering the key product of photosynthesis (carbohydrates) is crucial for understanding how plants contribute to energy storage in ecosystems.
Question 25. Carnivores feed upon
(a) Decomposers
(b) Herbivores
(c) Producers
(d) Secondary producers
Answer: (b) Herbivores
In simple words: Carnivores primarily feed on other animals, often herbivores (primary consumers) that eat plants, or other carnivores (secondary consumers).
🎯 Exam Tip: Defining carnivores as meat-eaters helps distinguish their role from herbivores and producers in an ecosystem's food web.
Question 26. is used up in the processes like respiration, combustion, decomposition, corrosion, rusting, etc.
(a) Nitrogen
(b) Oxygen
(c) Argon
(d) Helium
Answer: (b) Oxygen
In simple words: Oxygen is vital for many biological and chemical processes on Earth, including breathing (respiration), burning (combustion), and the breakdown of matter (decomposition, corrosion, rusting).
🎯 Exam Tip: Recognizing oxygen's broad involvement in metabolic and oxidative processes helps in understanding its importance in various cycles.
Question 27. Nitrogen forms % of the atmosphere.
(a) 79
(b) 78
(c) 21
(d) 2
Answer: (b) 78
In simple words: Nitrogen gas makes up the largest proportion of Earth's atmosphere, constituting approximately 78% of its volume.
🎯 Exam Tip: Knowing the atmospheric composition of key gases like nitrogen is fundamental to studying biogeochemical cycles.
Question 28. Most organisms cannot use the free form of
(a) Oxygen
(b) Nitrogen
(c) Carbon dioxide
(d) Carbon monoxide
Answer: (b) Nitrogen
In simple words: While abundant in the atmosphere, free atmospheric nitrogen (N2) cannot be directly utilized by most organisms and needs to be converted into usable forms by specific bacteria.
🎯 Exam Tip: This question highlights the importance of nitrogen fixation, a process that converts inert atmospheric nitrogen into biologically available compounds.
Question 29. first proposed the concept of Ecological Pyramid in 1927.
(a) Darwin
(b) Newton
(c) Elton
(d) Edison
Answer: (c) Elton
In simple words: Charles Elton was the ecologist who introduced the concept of the ecological pyramid, illustrating the trophic structure of ecosystems.
🎯 Exam Tip: Remembering Charles Elton's contribution is important for understanding the visual representation of energy or biomass distribution across trophic levels.
Question 30. Ecological Pyramid is called
(a) Hills
(b) Mounts
(c) Eltonian
(d) Darwinism
Answer: (c) Eltonian
In simple words: Ecological pyramids are often referred to as Eltonian pyramids in honor of Charles Elton, who first described them.
🎯 Exam Tip: The term "Eltonian pyramid" is an alternative name for ecological pyramids, emphasizing their historical origin in ecology.
Question 31. is produced from oxygen through various atmospheric processes.
(a) Nitrogen dioxide
(b) Nitrites
(c) Ozone
(d) CFC
Answer: (c) Ozone
In simple words: Ozone (O3) is formed in the atmosphere when oxygen molecules (O2) react with atomic oxygen (O) through processes often involving ultraviolet radiation.
🎯 Exam Tip: Understanding ozone formation is crucial for appreciating its role in protecting Earth from harmful UV radiation.
Question 32. Interactions between producers, consumers and saprophytes in a definite sequence is called
(a) Links
(b) Internet
(c) Food chain
(d) Connectors
Answer: (c) Food chain
In simple words: A food chain describes the linear feeding relationship where energy is transferred from one organism to another in a definite sequence.
🎯 Exam Tip: A food chain illustrates the direct flow of energy from producers through various consumers and decomposers.
Question 33. Many food chains interconnected at various levels is called
(a) Links
(b) Internet
(c) Connectors
(d) Food web
Answer: (d) Food web
In simple words: A food web is a complex network of interconnected food chains, showing multiple feeding relationships within an ecosystem.
🎯 Exam Tip: Food webs provide a more realistic representation of energy flow than simple food chains, as most organisms have varied diets.
Question 34. Decomposers dissipate some amount of energy in the form of
(a) Light
(b) Electricity
(c) Sound
(d) Heat
Answer: (d) Heat
In simple words: During the process of decomposition, decomposers release energy mostly as heat, which is then lost from the ecosystem.
🎯 Exam Tip: Energy flow in ecosystems is unidirectional and involves significant loss as heat at each trophic level, including decomposition.
Question 35. The flow of nutrients in an ecosystem is
(a) Non- cyclic
(b) Mono directional
(c) Reverse directional
(d) Cyclical
Answer: (d) Cyclical
In simple words: Nutrients in an ecosystem are continuously recycled through biogeochemical cycles, meaning their flow is cyclical rather than one-way.
🎯 Exam Tip: Distinguish between energy flow (one-way) and nutrient flow (cyclical) as a key concept in ecosystem dynamics.
Question 36. The cyclical flow of nutrients within an ecosystem is called
(a) Biological cycle
(b) Chemical cycle
(c) Solar cycle
(d) Bio-geo chemical cycle
Answer: (d) Bio-geo chemical cycle
In simple words: The continuous movement and recycling of chemical elements between living organisms and the non-living environment are termed biogeochemical cycles.
🎯 Exam Tip: The term "biogeochemical" highlights the involvement of biological, geological, and chemical processes in nutrient cycling.
Question 37. is an accumulation of the main abiotic gaseous nutrient materials found in the earth's atmosphere.
(a) Gaseous cycle
(b) Water cycle
(c) Solar cycle
(d) Lunar cycle
Answer: (a) Gaseous cycle
In simple words: Gaseous cycles, like the carbon and nitrogen cycles, involve the accumulation and exchange of nutrient elements primarily in the atmosphere.
🎯 Exam Tip: Gaseous cycles are characterized by a large atmospheric reservoir, allowing for relatively rapid circulation of nutrients.
Question 38. Oxygen is released into the atmosphere by the process of
(a) Photosynthesis
(b) Respiration
(c) Oxidation
(d) Decomposition
Answer: (a) Photosynthesis
In simple words: Photosynthesis by plants and other producers is the primary process that releases oxygen into the Earth's atmosphere.
🎯 Exam Tip: Photosynthesis is fundamental to sustaining aerobic life on Earth by producing oxygen and organic matter.
Question 39. Charles Elton studied the of the Beer islands in England..
(a) Tundra ecosystem
(b) Mediterranean ecosystem
(c) Equatorial ecosystem
(d) Taiga ecosystem
Answer: (a) Tundra ecosystem
In simple words: Charles Elton's foundational work on ecological pyramids and food chains was based on his studies of tundra ecosystems, notably in the Beer islands.
🎯 Exam Tip: Knowing the specific locations or ecosystems studied by key scientists can provide valuable context for their theories.
Question 40. in 1942 studied the food chain and energy flow through it.
(a) Charles Elton
(b) Lindeman
(c) Robert Whittaker
(d) Eichler
Answer: (b) Lindeman
In simple words: Raymond Lindeman's 1942 paper established the concept of energy flow through trophic levels in an ecosystem, which became a cornerstone of modern ecology.
🎯 Exam Tip: Lindeman's work on energy flow complements Elton's ecological pyramids by adding a quantitative dimension to trophic dynamics.
Question 41. After the death of apex consumers, energy becomes available to
(a) Primary consumer
(b) Secondary consumer
(c) Decomposer
(d) Sun
Answer: (c) Decomposer
In simple words: Upon the death of any organism, including apex consumers, decomposers break down their remains, releasing energy and nutrients back into the ecosystem.
🎯 Exam Tip: Decomposers play a crucial role in cycling matter and releasing energy that would otherwise be locked in dead organic material.
Question 42. Nitrogen forms % of the atmosphere.
(a) 28%
(b) 78%
(c) 48%
(d) 82%
Answer: (b) 78%
In simple words: Nitrogen is the most abundant gas in Earth's atmosphere, making up about 78 percent of its total volume.
🎯 Exam Tip: It is important to remember the approximate percentages of major gases like nitrogen and oxygen in the atmosphere.
Question 43. first proposed the concept of the Ecological Pyramid in 1927.
(a) Charles Elton
(b) Lindeman
(c) Eichler
(d) John Muir
Answer: (a) Charles Elton
In simple words: Charles Elton introduced the concept of ecological pyramids to graphically represent the quantitative relationships between different trophic levels.
🎯 Exam Tip: Charles Elton's work on ecological pyramids provided a simple, visual tool to understand the structure of ecosystems.
Question 44. Oxygen is released into the atmosphere by the process of
(a) respiration
(b) Photosynthesis
(c) Combustion
(d) All of these
Answer: (b) Photosynthesis
In simple words: Photosynthesis is the natural process carried out by plants and algae that uses sunlight to convert carbon dioxide and water into glucose and releases oxygen as a byproduct.
🎯 Exam Tip: Understanding the inputs and outputs of photosynthesis is crucial for comprehending the oxygen and carbon cycles.
Find The Odd Man Out:
Question 1. Photosynthesis, Respiration, Decomposition, Forest Fires
Answer: Forest Fires
In simple words: Forest fires are a destructive event, whereas photosynthesis, respiration, and decomposition are natural, biological processes essential for ecosystem function.
🎯 Exam Tip: Categorizing processes by their impact (constructive, destructive, or cyclical) helps in identifying the odd one out.
Question 2. Combustion, Corrosion, rusting, formation of ozone, Photosynthesis
Answer: Photosynthesis
In simple words: Photosynthesis produces oxygen, while combustion, corrosion, rusting, and ozone formation are all processes that consume oxygen or involve its chemical reactions.
🎯 Exam Tip: Focus on whether the process consumes or produces a common element or has a similar chemical nature to find the outlier.
Question 3. Biological nitrogen fixation, ammonification, nitrification, denitrification, industrial nitrogen fixation
Answer: Industrial nitrogen fixation
In simple words: Biological nitrogen fixation, ammonification, nitrification, and denitrification are natural processes within the nitrogen cycle, while industrial nitrogen fixation is an artificial, human-made process.
🎯 Exam Tip: Differentiate between natural biological/geological processes and human-induced activities when analyzing cycles.
Question 4. Frog, Owl, Squirrel, Fox
Answer: Squirrel
In simple words: Frogs, owls, and foxes are primarily carnivorous or omnivorous predators, while a squirrel is primarily a herbivore, feeding on nuts and seeds.
🎯 Exam Tip: Classifying organisms by their primary diet (herbivore, carnivore, omnivore) is useful for these types of questions.
Question 5. Grasshopper, squirrel, elephant, lion
Answer: Lion
In simple words: Grasshoppers, squirrels, and elephants are all herbivores (primary consumers), whereas a lion is a carnivore (secondary or tertiary consumer).
🎯 Exam Tip: Grouping animals by their trophic level or dietary habits can help identify the one that doesn't fit.
Question 6. Nitrogen cycle, oxygen cycle, carbon cycle, phosphorus cycle
Answer: Phosphorus cycle
In simple words: Nitrogen, oxygen, and carbon cycles are primarily gaseous biogeochemical cycles with large atmospheric reservoirs, while the phosphorus cycle is a sedimentary cycle, mainly involving the Earth's crust.
🎯 Exam Tip: Differentiating between gaseous and sedimentary cycles based on their primary reservoir is a key concept.
Question 7. Photosynthesis, Nitrification, Ammonification, Denitrification
Answer: Photosynthesis
In simple words: Nitrification, ammonification, and denitrification are all processes specific to the nitrogen cycle, whereas photosynthesis is the process of energy conversion in plants and a part of the carbon-oxygen cycle.
🎯 Exam Tip: Grouping processes by the specific biogeochemical cycle they belong to helps in identifying the odd one out.
Find Out The Correlation:
Question 1. Grasshopper : Primary consumer :: Tiger :
Answer: (1) Apex consumer
In simple words: A grasshopper eats producers, making it a primary consumer, while a tiger is at the top of the food chain, making it an apex consumer.
🎯 Exam Tip: Understand the trophic levels of common animals to establish correlations in food chains.
Question 2. Owl : Secondary consumer :: Squirrel :
Answer: (2) Primary consumer
In simple words: An owl typically eats primary consumers, making it a secondary consumer, whereas a squirrel eats plants, classifying it as a primary consumer.
🎯 Exam Tip: Correctly identify the dietary role of organisms to determine their trophic level.
Question 3. Flow of energy : One way :: Flow of nutrients :
Answer: (3) Cyclic
In simple words: Energy moves through an ecosystem in one direction, while nutrients are constantly recycled in a cyclical manner.
🎯 Exam Tip: This correlation highlights a fundamental difference between energy and nutrient dynamics in ecosystems.
Question 4. Plants: Producers :: Bacteria and Fungi :
Answer: (4) Decomposers
In simple words: Plants produce their own food (producers), while bacteria and fungi break down dead organic matter (decomposers).
🎯 Exam Tip: Clearly defining the ecological roles of different organism groups is essential.
Question 5. Nitrogen: Gaseous cycle :: Phosphorus :
Answer: (5) Sedimentary cycle
In simple words: Nitrogen primarily cycles through the atmosphere (gaseous), whereas phosphorus is mainly stored and cycled within rocks and soil (sedimentary).
🎯 Exam Tip: Differentiating between gaseous and sedimentary biogeochemical cycles based on their major reservoir is a key concept.
Question 6. Oxygen : 21% :: Nitrogen :
Answer: (6) 78%
In simple words: Oxygen constitutes about 21% of the atmosphere, while nitrogen makes up approximately 78%.
🎯 Exam Tip: Memorizing the percentages of major atmospheric gases is important for general science knowledge.
Question 7. Photosynthesis: Carbon cycle:: Ammonification :
Answer: (7) Nitrogen cycle
In simple words: Photosynthesis is a key process in the carbon cycle, while ammonification is a crucial step in the nitrogen cycle.
🎯 Exam Tip: Connect specific processes to their respective biogeochemical cycles.
Question 8. Respiration : Oxygen cycle :: Nitrification :
Answer: (8) Nitrogen cycle
In simple words: Respiration is a process involved in the oxygen cycle, while nitrification is a specific step in the nitrogen cycle where ammonia is converted to nitrites and nitrates.
🎯 Exam Tip: Understand which major biological processes drive each biogeochemical cycle.
Question 9. Respiration : Biotic process :: Combustion :
Answer: (9) Abioticprocess
In simple words: Respiration is a biological process carried out by living organisms, whereas combustion is a non-biological (abiotic) chemical process, often involving burning.
🎯 Exam Tip: Differentiate between processes driven by living organisms (biotic) and those by physical or chemical factors (abiotic).
Question 10. Microbes using oxygen : Aerobes :: Microbes not using oxygen :
Answer: (10) Anaerobes
In simple words: Microbes that require oxygen for survival are aerobes, while those that do not require oxygen are anaerobes.
🎯 Exam Tip: Understanding the distinction between aerobic and anaerobic organisms is fundamental in microbiology and ecology.
Q.I. (B) 3. Difference Between:
Question (1) Azotobacter and Rhizobium
Answer:
| Azotobacter | Rhizobium |
| Free-living nitrogen-fixing bacteria | Symbiotic nitrogen-fixing bacteria |
In simple words: Azotobacter are bacteria that fix nitrogen while living freely in the soil, whereas Rhizobium are bacteria that fix nitrogen symbiotically, residing in the root nodules of leguminous plants.
🎯 Exam Tip: Differentiate between free-living and symbiotic nitrogen-fixing bacteria by their lifestyle and association with plants.
Question (2) Biotic components and Abiotic component
Answer:
| Biotic components | Abiotic component |
| Living component of an ecosystem | Physical/Chemical non-living components of an ecosystem |
In simple words: Biotic components refer to all living organisms in an ecosystem, while abiotic components are the non-living physical and chemical factors.
🎯 Exam Tip: Understanding the clear distinction between living (biotic) and non-living (abiotic) factors is fundamental to ecology.
Question (3) Producers and Herbivores
Answer:
| Producers | Herbivores |
| They are present in the 1st trophic level | They are present in the 2nd trophic level |
In simple words: Producers, like plants, create their own food and form the base of the food chain, while herbivores are primary consumers that feed directly on these producers.
🎯 Exam Tip: Always remember that producers are the first trophic level, and herbivores are the second, directly consuming producers.
Question (4) Carnivores and Herbivores
Answer:
| Carnivores | Herbivores |
| They depend on Herbivores for nutrition | They depend on Producers for nutrition |
In simple words: Carnivores obtain energy by eating other animals (often herbivores), whereas herbivores get their energy by consuming plants (producers).
🎯 Exam Tip: Differentiate between carnivores and herbivores by their primary food source to correctly identify their roles in the food chain.
Question (5) Phosphorus and Carbon
Answer:
| Phosphorus | Carbon |
| It cycles through the Sedimentary cycle | It cycles through the Gaseous cycle |
In simple words: The phosphorus cycle is primarily sedimentary, involving rocks and soil, while the carbon cycle is largely gaseous, with a significant atmospheric reservoir.
🎯 Exam Tip: Classifying biogeochemical cycles as either gaseous or sedimentary based on their main reservoir helps in understanding their dynamics.
Question (6) Food chain and Food web
Answer:
| Food chain | Food web |
| Interactions between producers, consumers and decomposers in a definite sequence is called as a food chain. | The interconnection among different food chains in an ecosystem at various levels is called as a food web |
In simple words: A food chain shows a single, linear path of energy transfer, whereas a food web illustrates the complex, interconnected feeding relationships among multiple food chains in an ecosystem.
🎯 Exam Tip: Remember that a food web is a more realistic representation of energy flow than a simple food chain due to the varied diets of most organisms.
State Whether The Following Statements Are True Or False. Correct The False Statements:
Question (1) Herbivores occupy the third trophic level in a food chain.
Answer: False, herbivores occupy the second trophic level in a food chain as they are directly dependent on producers.
In simple words: Herbivores are primary consumers that eat plants, placing them at the second trophic level, not the third.
🎯 Exam Tip: Clearly define the trophic levels: producers (1st), herbivores (2nd), primary carnivores (3rd), etc.
Question (2) Apex consumers use herbivores and carnivores as their food.
Answer: True
In simple words: Apex consumers are top predators that can feed on both plant-eating animals (herbivores) and other meat-eating animals (carnivores).
🎯 Exam Tip: Apex consumers are at the highest trophic level and typically prey on various types of consumers below them.
Question (3) Humans are apex consumers.
Answer: True
In simple words: Humans can be considered apex consumers in many food chains as they consume a wide variety of producers, herbivores, and carnivores, often having no natural predators themselves.
🎯 Exam Tip: Recognize humans' versatile dietary habits, allowing them to occupy various trophic levels, often as apex consumers.
Question (4) False. Omnivores feed on both herbivores and carnivores.
Answer: False. Omnivores feed on both herbivores and carnivores.
In simple words: Omnivores consume both plants and animals, which means they can eat producers, herbivores, and other carnivores.
🎯 Exam Tip: An omnivore's diet includes a mix of plant and animal matter, distinguishing them from strict herbivores or carnivores.
Question (5) False. A food chain consists of four, five or more links.
Answer: False. A food chain consists of four, five or more links.
In simple words: A food chain can consist of varying numbers of links, not necessarily limited to four, five, or more; it depends on the ecosystem.
🎯 Exam Tip: The length of a food chain is variable and typically limited by energy transfer efficiency, rarely exceeding 4-5 trophic levels.
Question (6) False. A food web can have many consumers.
Answer: False. A food web can have many consumers.
In simple words: A food web is a complex network of feeding relationships and typically includes many different consumers at various trophic levels.
🎯 Exam Tip: Food webs demonstrate the interconnectedness and diversity of feeding relationships, involving numerous consumers.
Question (7) False. The amount of matter and energy goes on decreasing at every level in a food chain.
Answer: False. The amount of matter and energy goes on decreasing at every level in a food chain.
In simple words: While energy decreases significantly at each trophic level (due to the 10% rule), matter is recycled, and its total amount within the ecosystem remains conserved, although its form changes.
🎯 Exam Tip: Differentiate between the flow of energy (unidirectional and decreasing) and the cycling of matter (recycled) in an ecosystem.
Question (8) False. Charles Elton first proposed the concept of Ecological Pyramid.
Answer: False. Charles Elton first proposed the concept of Ecological Pyramid.
In simple words: Charles Elton is credited with proposing the concept of ecological pyramids in 1927.
🎯 Exam Tip: Correctly attribute key ecological concepts to their discoverers to avoid common misconceptions.
Question (9) True
Answer: True
In simple words: Upon the death of apex consumers, decomposers break down their organic matter, making the stored energy available for nutrient cycling.
🎯 Exam Tip: Decomposers are vital for recycling nutrients and energy from all dead organisms, regardless of their trophic level.
Question (10) True
Answer: True
In simple words: Gaseous cycles, like the carbon and nitrogen cycles, have large atmospheric reservoirs that allow for faster circulation compared to sedimentary cycles, which involve slow geological processes.
🎯 Exam Tip: Understand that the mobility of the reservoir (atmosphere vs. lithosphere) dictates the speed of nutrient cycling.
Question (11) True
Answer: True
In simple words: Human activities such as pollution and deforestation, along with natural climatic changes, can significantly disrupt the balance and speed of biogeochemical cycles.
🎯 Exam Tip: Recognize the various anthropogenic and natural factors that impact the equilibrium of Earth's critical biogeochemical cycles.
Question (12) False. Carbon dioxide is released in the atmosphere through respiration, burning of fossil fuels and wood, forest fires and volcanic activity. (13) False. The equilibrium of oxygen and carbon dioxide gases is maintained by plants.
Answer: False. Carbon dioxide is released in the atmosphere through respiration, burning of fossil fuels and wood, forest fires and volcanic activity. (13) False. The equilibrium of oxygen and carbon dioxide gases is maintained by plants.
In simple words: Carbon dioxide is primarily released through respiration, combustion of fossil fuels and biomass, and volcanic eruptions. The equilibrium of oxygen and carbon dioxide is maintained by plants (through photosynthesis) and other organisms/processes (through respiration and decomposition).
🎯 Exam Tip: Be precise about the processes that release carbon dioxide and the primary agents responsible for maintaining atmospheric gas balance.
Question (14) False. The conversion of ammonia into a nitrite and then nitrate is called nitrification.
Answer: False. The conversion of ammonia into a nitrite and then nitrate is called nitrification.
In simple words: The biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate is specifically known as nitrification.
🎯 Exam Tip: Memorize the specific terms for each step in the nitrogen cycle (e.g., nitrogen fixation, ammonification, nitrification, denitrification).
Question (15) False. Conversion of nitrogen compounds into gaseous nitrogen is called denitrification.
Answer: False. Conversion of nitrogen compounds into gaseous nitrogen is called denitrification.
In simple words: Denitrification is the process where bacteria convert nitrates back into gaseous nitrogen, releasing it into the atmosphere.
🎯 Exam Tip: Understand denitrification as the final step in the nitrogen cycle that returns nitrogen gas to the atmosphere.
Question (16) True
Answer: True
In simple words: Ammonification is the process by which decomposers break down nitrogenous organic matter from dead organisms and excretory wastes into ammonia.
🎯 Exam Tip: Ammonification is a crucial early step in the nitrogen cycle, making nitrogen available for other transformations.
Question (17) False. The cyclic flow of nutrients within an ecosystem is called Energy Pyramid.
Answer: False. The cyclic flow of nutrients within an ecosystem is called bio-geochemical cycle.
In simple words: The cyclic movement of nutrients between living and non-living components of an ecosystem is termed a biogeochemical cycle, not an energy pyramid, which depicts energy flow.
🎯 Exam Tip: Distinguish clearly between an energy pyramid (energy flow) and biogeochemical cycles (nutrient recycling).
Name The Following:
Question 1. The animals that feed on herbivores.
Answer: Carnivores.
In simple words: Carnivores are animals that primarily eat other animals, including herbivores.
🎯 Exam Tip: Understanding the dietary classifications helps in categorizing organisms within a food web.
Question 2. Organisms that feed on herbivores and carnivores.
Answer: Omnivores.
In simple words: Omnivores are organisms whose diet consists of both plant and animal matter, meaning they can consume herbivores and carnivores.
🎯 Exam Tip: Omnivores occupy multiple trophic levels due to their varied diet.
Question 3. Two examples of primary consumers.
Answer: Grasshopper, squirrel.
In simple words: Primary consumers are herbivores that feed directly on producers like plants, such as grasshoppers eating grass or squirrels eating nuts.
🎯 Exam Tip: Identify primary consumers by observing which organisms directly consume producers.
Question 4. Two examples of secondary consumers.
Answer: Frog, owl.
In simple words: Secondary consumers are carnivores or omnivores that feed on primary consumers; frogs eat insects, and owls eat small rodents.
🎯 Exam Tip: Secondary consumers obtain energy by preying on herbivores or primary omnivores.
Question 5. Two examples of Apex consumers.
Answer: Lion, tiger.
In simple words: Apex consumers are top predators in an ecosystem, such as lions and tigers, which are not typically preyed upon by other animals.
🎯 Exam Tip: Apex consumers are at the highest trophic level and signify the end of a food chain.
Question 6. Levels in the food chain.
Answer: Trophic level.
In simple words: Each step or level in a food chain, representing the position an organism occupies, is called a trophic level.
🎯 Exam Tip: Trophic levels categorize organisms based on how they obtain energy, starting with producers.
Question 7. Organisms that decompose the dead bodies of plants and animals.
Answer: Decomposers.
In simple words: Decomposers, like bacteria and fungi, break down dead organic matter, playing a vital role in nutrient recycling.
🎯 Exam Tip: Decomposers are essential for returning nutrients from dead organisms back to the ecosystem for reuse by producers.
Question 8. Process which releases oxygen.
Answer: Photosynthesis.
In simple words: Photosynthesis is the biological process by which green plants and some other organisms convert light energy into chemical energy, releasing oxygen as a byproduct.
🎯 Exam Tip: Photosynthesis is the primary natural source of atmospheric oxygen.
Question 9. Release of ammonia through decomposition of dead bodies and excretory wastes of organisms.
Answer: Ammonification.
In simple words: Ammonification is the process where decomposers convert organic nitrogen from dead organisms and waste into ammonia.
🎯 Exam Tip: Ammonification is a crucial step that makes nitrogen available in a form that can be further processed in the nitrogen cycle.
Question 10. Conversion of nitrogen into nitrates and nitrites through atmospheric, industrial and biological processes.
Answer: Nitrogen fixation.
In simple words: Nitrogen fixation is the process of converting atmospheric nitrogen gas into forms like ammonia, nitrites, and nitrates, which are usable by plants.
🎯 Exam Tip: Nitrogen fixation is the initial step that makes atmospheric nitrogen available for entry into the biological nitrogen cycle.
One Line Answers:
Question 1. What is Food chain?
Answer: Interactions between producers, consumers and decomposers in a definite sequence is called as a food chain.
In simple words: A food chain describes a linear pathway of who eats whom, showing how energy moves from producers to consumers to decomposers.
🎯 Exam Tip: Remember that a food chain shows a direct, sequential transfer of energy.
Question 2. What is Food web?
Answer: The interconnection among different food chains in an ecosystem at various levels is called as a food web.
In simple words: A food web is a network of interconnected food chains that illustrates the complex feeding relationships within an ecosystem.
🎯 Exam Tip: Food webs provide a more comprehensive view of energy flow than individual food chains, accounting for diverse diets.
Question 3. What is Trophic level?
Answer: A trophic level is the step at which the organism obtains its food in the chain.
In simple words: A trophic level defines an organism's position in a food chain based on its primary food source.
🎯 Exam Tip: Trophic levels are foundational to understanding energy transfer and ecological pyramids.
Question 4. What is Pyramid of energy?
Answer: The pattern of energy exchange in an ecosystem is called a 'Pyramid of energy'.
In simple words: An energy pyramid graphically represents the amount of energy available at each trophic level, showing a decrease from base to apex.
🎯 Exam Tip: Energy pyramids are always upright, demonstrating the 10% rule of energy transfer between trophic levels.
Question 5. What is Bio-geo-chemical cycle?
Answer: The cyclical flow of nutrients within an ecosystem is called bio-geo-chemical cycle.
In simple words: A biogeochemical cycle is the pathway through which chemical elements move between biotic (living) and abiotic (non-living) components of an ecosystem.
🎯 Exam Tip: The term emphasizes the combined biological, geological, and chemical processes involved in nutrient recycling.
Question 6. What is Carbon cycle?
Answer: The circulation and recycling of carbon from the atmosphere to living organisms and aher their death back to the atmosphere is called the carbon cycle.
In simple words: The carbon cycle is the natural process where carbon atoms continuously travel from the atmosphere to Earth and then back into the atmosphere through various forms.
🎯 Exam Tip: The carbon cycle is vital for life, involving photosynthesis, respiration, decomposition, and combustion.
Question 7. What is Oxygen cycle?
Answer: The circulation and recycling of oxygen within the biosphere is called as oxygen cycle.
In simple words: The oxygen cycle describes how oxygen moves through Earth's atmosphere, hydrosphere, and lithosphere, used and produced by various processes.
🎯 Exam Tip: Photosynthesis and respiration are the two main biological processes driving the oxygen cycle.
Distinguish Between:
Question 1. Gaseous Cycle and Sedimentary Cycle.
Answer:
| Gaseous Cycle | Sedimentary Cycle |
| (i) It is an accumulation of the main abiotic gaseous nutrient materials found in the earth's atmosphere. | (i) It is an accumulation of the main abiotic nutrient materials found in the soil, sediment and sedimentary rocks, etc. of the earth. |
| (ii) It includes nitrogen, oxygen, carbon dioxide, water vapour etc. | (ii) It includes soil components like iron, calcium, phosphorus etc. |
In simple words: Gaseous cycles involve nutrients accumulating in the atmosphere (like nitrogen and oxygen), while sedimentary cycles involve nutrients accumulating in the Earth's crust (like phosphorus and calcium) through geological processes. Both are crucial for nutrient circulation in ecosystems.
🎯 Exam Tip: Understanding the primary reservoir (atmosphere vs. Earth's crust) and key elements for each cycle type is essential for distinguishing them and scoring well.
Question 2. Carbon Cycle and Nitrogen Cyde.
Answer:
| Carbon Cycle | Nitrogen Cycle |
| (i) The circulation and recycling of carbon from the atmosphere to living organisms and after their death back to the atmosphere is called the carbon cycle. | (i) The circulation and recycling of nitrogen into the form of different compounds through various biotic and abiotic processes in nature is called the nitrogen cycle. |
| (ii) Main processes involved in the carbon cycle are photosynthesis and respiration. | (ii) Main processes involved in the nitrogen cycle are nitrogen fixation, ammonification, nitrification and denitrification. |
| (iii) Carbon in the form of carbon dioxide is directly absorbed by plants for photosynthesis. | (iii) Nitrogen gas cannot be directly absorbed by plants. So nitrogen is fixed by the process of nitrogen fixation and then absorbed from the soil. |
In simple words: The carbon cycle involves carbon moving between the atmosphere, living organisms, and back, primarily through photosynthesis and respiration. The nitrogen cycle involves nitrogen gas being converted into usable forms by microbes and then circulated through ecosystems before returning to the atmosphere.
🎯 Exam Tip: Focus on the main processes and the primary forms of the elements in each cycle. The direct absorption of carbon dioxide by plants versus the multi-step fixation for nitrogen is a key differentiator.
Complete The Flow Chart:
Question 1. Energy Pyramid.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक जलीय पारिस्थितिकी तंत्र में ऊर्जा के पिरामिड को दर्शाता है। पिरामिड के आधार पर फाइटोप्लैंकटन (प्राथमिक उत्पादक) हैं, जिनमें 10,000 किलोकैलोरी ऊर्जा है। इसके ऊपर ज़ोओप्लैंकटन (प्राथमिक उपभोक्ता) हैं, जिनमें 1000 किलोकैलोरी ऊर्जा है। फिर मछलियां (द्वितीयक उपभोक्ता) हैं, जिनमें 100 किलोकैलोरी ऊर्जा है, और शीर्ष पर मनुष्य (तृतीयक उपभोक्ता) हैं, जिनमें 10 किलोकैलोरी ऊर्जा है। यह दर्शाता है कि प्रत्येक पोषी स्तर पर ऊर्जा कैसे घटती जाती है।
| 10 kcal | ||
| Humans | ||
| 100 kcal | ||
| Fishes | ||
| 1000 kcal | ||
| Zooplanktons | ||
| 10,000 kcal | ||
| Phytoplanktons | ||
| Pyramid of energy in an aquatic ecosystem | ||
Answer: The provided diagram is already a complete flow chart representing the energy pyramid in an aquatic ecosystem. It visually demonstrates the decrease in energy at successively higher trophic levels, starting from phytoplanktons at the base with 10,000 kcal, followed by zooplanktons (1000 kcal), fishes (100 kcal), and humans at the apex (10 kcal).
In simple words: The energy pyramid illustrates how energy decreases as it moves up through different feeding levels in an ecosystem, with producers having the most energy and apex consumers having the least.
🎯 Exam Tip: When completing flow charts related to energy pyramids, ensure the energy values decrease significantly with each ascending trophic level, typically by about 90% at each transfer, demonstrating the 10% law of energy transfer.
Question 2.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र पारिस्थितिकी तंत्र (Ecosystem) के विभिन्न प्रकारों और उनके उप-प्रकारों का एक प्रवाह चार्ट दर्शाता है। पारिस्थितिकी तंत्र को दो मुख्य श्रेणियों में बांटा गया है: प्राकृतिक (Natural Ecosystem) और मानव निर्मित/कृत्रिम (Manmade/Artificial Ecosystem)। प्राकृतिक पारिस्थितिकी तंत्र को आगे स्थलीय (Terrestrial Ecosystem) और जलीय (Aquatic Ecosystem) में विभाजित किया गया है। स्थलीय पारिस्थितिकी तंत्र में वन, घास के मैदान और रेगिस्तान शामिल हैं, जबकि जलीय पारिस्थितिकी तंत्र में समुद्री जल और ताजे पानी के प्रकार शामिल हैं।
| Ecosystem | ||||
| Natural Ecosystem | Manmade/Artificial Ecosystem | |||
| Terrestrial Ecosystem | Aquatic Ecosystem | |||
| Forest | Grassland | Desert | Marine water | Fresh water |
Answer: The provided flow chart accurately categorizes ecosystems into natural and man-made/artificial types. Natural ecosystems are further divided into terrestrial (forest, grassland, desert) and aquatic (marine water, fresh water) environments, illustrating a comprehensive classification framework.
In simple words: Ecosystems are classified as either natural (like forests or oceans) or man-made (like farms), and natural ones are further split into land-based (terrestrial) and water-based (aquatic) types, each with unique features.
🎯 Exam Tip: For ecosystem classification, clearly differentiate between natural and artificial types, and remember the common examples for terrestrial (forest, grassland, desert) and aquatic (marine, fresh water) categories to score full marks.
Question 3. Nitrogen Cycle
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र नाइट्रोजन चक्र को दर्शाता है, जिसमें वातावरण में मौजूद नाइट्रोजन गैस (N2) को विभिन्न चरणों से गुजारा जाता है। नाइट्रोजन स्थिरीकरण (Nitrogen fixation) वायुमंडलीय नाइट्रोजन को नाइट्रेट्स और नाइट्राइट्स में परिवर्तित करता है। अमोनिकरण (Ammonification) जीवों के मृत शरीरों और उत्सर्जी पदार्थों से अमोनिया (NH3) छोड़ता है। इसके बाद, नाइट्रीकरण (Nitrification) अमोनिया को नाइट्राइट (NO2) और फिर नाइट्रेट (NO3) में बदलता है। अंत में, डिनिट्रीकरण (Denitrification) नाइट्रोजन यौगिकों को गैसीय नाइट्रोजन में वापस परिवर्तित करता है, जो वायुमंडल में लौट जाती है।
 which are very stable and not degraded by any biological process) were found to persist in the atmosphere. Once they reached the ozone layer, they would react with the ozone molecules. This resulted in a reduction of the ozone layer and recently they have discovered a hole in the ozone layer above the Antarctica. It is difficult to imagine the consequences for life on Earth if the ozone layer dwindles further, but many people think that it would be better not to take chances. These people advocate working towards stopping all further damage to the ozone layer.</p><p>The utilisation of glucose to provide energy to living things involves the process of respiration in which oxygen may or may not be used to convert glucose back into carbon dioxide. This carbon dioxide then goes back into the atmosphere. Another process that adds to the carbon dioxide in the atmosphere is the process of combustion where fuels are burnt to provide energy for various needs like heating, cooking, transportation and industrial processes.</p><p>In fact, the percentage of carbon dioxide in the atmosphere is said to have doubled since the industrial revolution when human beings started burning fossil fuels on a very large scale. Carbon, like water, is thus cycled repeatedly through different forms by the various physical and biological activities. Heat is trapped by glass, and hence the temperature inside a glass enclosure will be much higher than the surroundings. This phenomenon was used to create an enclosure where tropical plants could be kept warm during the winters in colder climates. Such enclosures are called greenhouses.</p><p>Greenhouses have also lent their name to an atmospheric phenomenon. Some gases prevent the escape of heat from the Earth. An increase in the percentage of such gases in the atmosphere would cause the average temperatures to increase worldwide and this is called the greenhouse effect. Carbon dioxide is one of the greenhouse gases. An increase in the carbon dioxide content in the atmosphere would cause more heat to be retained by the atmosphere and lead to global warming.</p><p>Nitrogen gas makes up 78% of our atmosphere and nitrogen is also a part of many molecules essential to life like proteins, nucleic acids (DNA and RNA) and some vitamins. Nitrogen is found in other biologically important compounds such as alkaloids and urea too. Nitrogen is thus an essential nutrient for all life-forms and life would be simple if all these life-forms could use the atmospheric nitrogen directly. However, other than a few forms of bacteria, life-forms are not able to convert the comparatively inert nitrogen molecule into forms like nitrates and nitrites which can be taken up and used to make the required molecules.</p><p>These nitrogen-fixing bacteria may be free-living or be associated with some species of dicot plants. Most commonly, the nitrogenfixing bacteria are found in the roots of legumes (generally the plants which give us pulses) in special</p><p>structures called root nodules. Other than these bacteria, the only other manner in which the nitrogen molecule is converted to nitrates and nitrites is by a physical process. During lightning, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen. These oxides dissolve in water to give nitric and nitrous acids and fall on land along with rain. These are then utilised by various lifeforms.</p><p><strong>Read The Paragraph And Answer The Questions:</strong></p><p><strong>(1) Nitrogen Cycle</strong></p><p>The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among the atmosphere, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification, The majority of Earth's atmosphere (78%) is atmosphere nitrogen, making it the largest source of nitrogen.</p><p>However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition, Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle. Human modification of the global nitrogen cycle can negatively affect the natural environment system and also human health.</p><p></p><p><strong>(i) Why nitrogen cycle is called bio-geochemical cycle?</strong><br /><span style=)
Answer: Nitrogen cycle is called bio-geochemical cycle as it undergoes biological as well as geochemical processes.
In simple words: The nitrogen cycle is called biogeochemical because it involves both living (biological) organisms and non-living (geological and chemical) components of the Earth's system in the movement and transformation of nitrogen.
🎯 Exam Tip: When explaining why a cycle is 'bio-geochemical', always mention the involvement of both living organisms and non-living environmental components.
(ii) Why is nitrogen cycle important to us?
Answer: Nitrogen cycle is important to us as nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition.
In simple words: The nitrogen cycle is crucial for life because nitrogen is a key component of proteins and nucleic acids, which are essential for the growth and functioning of all organisms.
🎯 Exam Tip: For importance questions, link the nutrient to its role in biological molecules (e.g., proteins, DNA) and ecosystem processes.
(iii) Name important process of nitrogen cycle.
Answer: Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification.
In simple words: The key processes of the nitrogen cycle are nitrogen fixation (converting atmospheric nitrogen to usable forms), ammonification (producing ammonia from organic matter), nitrification (converting ammonia to nitrites and nitrates), and denitrification (returning nitrogen gas to the atmosphere).
🎯 Exam Tip: Remember the four main processes of the nitrogen cycle: fixation, ammonification, nitrification, and denitrification, as they are often asked in exams.
(iv) What can affect the nitrogen cycle negatively?
Answer: Human modification of the global nitrogen cycle can negatively affect the natural environment system and also human health.
In simple words: Human activities significantly alter the natural nitrogen cycle, leading to imbalances that can harm both ecosystems and human health.
🎯 Exam Tip: When discussing negative impacts, focus on human activities and their broad consequences for the environment and health.
(v) Which human activities change the nitrogen cycle?
Answer: Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle.
In simple words: Burning fossil fuels, using synthetic fertilizers, and discharging wastewater are major human activities that disrupt the natural balance of the nitrogen cycle.
🎯 Exam Tip: List specific human activities (fossil fuels, fertilizers, wastewater) when asked about human impacts on nutrient cycles for a complete answer.
(2) Food Web
A food chain is a linear network of links in a food i web starting from producer organisms (such asgrass or trees which use radiation from the Sun to make their food) and ending at apex predator species (like grizzly bears or killer whales), detritivores (like earthworms or woodlice), ordecomposer species (such as fungi or bacteria), A food chain also shows how the organisms are related with each other by the way they eat. Each level of a food chain represents a different trophiclevel. A food chain differs from a food web, because the complex network of different animal's feeding relations are aggregated and the chain only follows a direct, linear pathway of one animal at a time.
Natural interconnections between food chains make it a food web. A common metric usedto the quantify food web trophic structure is foodi chain length. In its simplest form, the length of a chain is the number of links between a trophici consumer and the base of the web and the meanchain length of an entire web is the arithmetic average of the lengths of all chains in a food web. The food chain is an energy source diagram. Many food webs have a keystone species. A keystonespecies is a species that has a large impact on thei surrounding environment and can directly affectthe food chain.
If this keystone species dies off it can set the entire food chain off balance. Keystonespecies keep herbivores from depleting all of thei foliage in their
environment and preventing ai mass extinction. Food chains were first introduced by the Arab scientist and philosopher Al-Jahiz inthe 10th century and later popularized in a book I published in 1927 by Charles Elton, which also i introduced the food web concept.
(i) What is a food web?
Answer: Food web is a linear network of links of food chains.
In simple words: A food web is a complex system of interconnected food chains in an ecosystem, showing who eats whom.
🎯 Exam Tip: Differentiate between a food chain (linear) and a food web (interconnected multiple chains) clearly in your definitions.
(ii) In a food web which organism are called producers?
Answer: In a food web which organism which can produce food by photosynthesis are called producers.
In simple words: Producers are organisms, mainly plants and algae, that create their own food through photosynthesis, forming the base of the food web.
🎯 Exam Tip: Always associate producers with photosynthesis and their role as the primary energy source in an ecosystem.
(iii) What is the role of keystone species?
Answer: Keystone species keep herbivores from depleting all of the foliage in their environment and preventing a mass extinction.
In simple words: Keystone species are critical for maintaining ecosystem balance, often by controlling herbivore populations and preserving plant life, thus preventing ecological collapse.
🎯 Exam Tip: Highlight the disproportionately large impact of keystone species on their ecosystem relative to their abundance.
(iv) What is a keystone species?
Answer: A keystone species is a species that has a large impact on the surrounding environment and can directly affect the food chain.
In simple words: A keystone species is one whose presence is essential for maintaining the structure and health of its ecosystem, having a significant effect on other species and the food web.
🎯 Exam Tip: Ensure your definition of a keystone species emphasizes its significant impact on the ecosystem, not just its role in the food chain.
(v) What does each level of food chain represent?
Answer: Each level of a food chain represents a different trophic level.
In simple words: Each stage in a food chain, showing where an organism obtains its energy, is called a trophic level.
🎯 Exam Tip: Understand that trophic levels categorize organisms by their position in the food chain based on how they acquire energy.
(3) Carbon Cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major component of many minerals such as limestone. Along with the nitrogen cycle and the water cycle, the carbon cycle comprises a sequence of events that are key to make Earth capable of sustaining life. It describes the movement of
carbon as it is recycled and reused throughout the biosphere, as well as long-term processes of carbon sequestration to and release from carbon sinks.
The carbon cycle was discovered by Antoine! Lavoisier and Joseph Priestley, and popularised by Humphry Davy. Carbon in the Earth'satmosphere exists in two main forms carbon dioxide and methane. Both of these gases absorb and retain heat in the atmosphere and are partially responsible for the greenhouse effect. Methane produces a larger greenhouse effect per volume as compared to carbon dioxide, but it exists in much lower concentrations and is more short-lived than carbon dioxide, making carbon dioxide the more important greenhouse gas of the two.
Carbon dioxide is removed from the atmosphere primarily through photosynthesis and enters the terrestrial and oceanic biospheres. Carbon dioxide also dissolves directly from the atmosphere into bodies of water (ocean, lakes, etc.), as well as dissolving in precipitation as raindrops fall through the atmosphere. When dissolved in water, carbon dioxide reacts with water molecules and forms carbonic acid, which contributes to ocean acidity. It can then be absorbed by rocks through weathering. It also can acidify other surfaces it touches or be washed into the ocean.
(i) Which gas has greener house effect as compared to CO2?
Answer: Methane gas CH4 has greener house effect as compared to CO2.
In simple words: Methane (CH4) causes a stronger greenhouse effect than carbon dioxide (CO2) per molecule, even though it is less abundant and shorter-lived in the atmosphere.
🎯 Exam Tip: Remember that while CO2 is more prevalent, methane has a significantly higher global warming potential per unit mass.
(ii) How does dissolved CO2 affect oceans?
Answer: When dissolved in water, carbon dioxide reacts with water molecules and forms carbonic acid, which contributes to ocean acidity.
In simple words: Carbon dioxide dissolving in oceans creates carbonic acid, leading to ocean acidification which harms marine life and ecosystems.
🎯 Exam Tip: Focus on the chemical reaction (CO2 + H2O -> H2CO3) and its ecological consequence (ocean acidification) when explaining CO2's effect on oceans.
(iii) Why is carbon cycle called bio-geochemical cycle?
Answer: The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.
In simple words: The carbon cycle is termed biogeochemical because carbon moves through living organisms (bio), geological formations (geo), and chemical processes across Earth's spheres.
🎯 Exam Tip: When defining a biogeochemical cycle, specify its circulation through biotic (biosphere) and abiotic (atmosphere, hydrosphere, geosphere) components.
(iv) How is carbon dioxide removed from atmosphere?
Answer: Carbon dioxide is removed from the atmosphere primarily through photosynthesis and enters the terrestrial and oceanic biospheres.
In simple words: Photosynthesis by plants and absorption by oceans are the main ways carbon dioxide is naturally taken out of the atmosphere.
🎯 Exam Tip: Highlight photosynthesis and oceanic absorption as the primary natural mechanisms for CO2 removal from the atmosphere.
(v) Who discovered the carbon cycle?
Answer: The carbon cycle was discovered by Antoine Lavoisier and Joseph Priestley.
In simple words: Antoine Lavoisier and Joseph Priestley are credited with discovering the fundamental aspects of the carbon cycle.
🎯 Exam Tip: For historical questions, accurately recall the names of scientists associated with key discoveries.
Answer The Questions In Detail:
Question 1. Write the important processes of the nitrogen cycle.
Answer:
- Nitrogen fixation- Conversion of nitrogen into nitrates and nitrites through atmospheric, industrial and biological processes.
- Ammonification- Release of ammonia through decomposition of dead bodies and excretory wastes of organisms.
- Nitrification- Conversion of ammonia into a nitrite and then nitrate.
- Denitrification- Conversion of nitrogen components into gaseous nitrogen.
In simple words: The nitrogen cycle involves nitrogen fixation (N2 to nitrates/nitrites), ammonification (organic N to ammonia), nitrification (ammonia to nitrates), and denitrification (nitrates to N2 gas), all crucial for nitrogen's circulation in ecosystems.
🎯 Exam Tip: When listing processes, define each clearly and concisely. For nitrogen cycle, ensure all four key stages are mentioned with their transformations.
Make A Concept Diagram And Explain.
Question 1. Food chain
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक स्थलीय खाद्य श्रृंखला को दर्शाता है। इसमें दिखाया गया है कि कैसे सूर्य के प्रकाश से घास उगती है, हिरण घास खाता है, और फिर बाघ हिरण का शिकार करता है। यह ऊर्जा के प्रवाह की एक सीधी कड़ी को प्रदर्शित करता है, जिसमें प्रत्येक जीव अगले के लिए भोजन बनता है।
Answer: According to the mode of nutrition the organisms are classified into producers, consumers, saprotrophs (saprophytes) and decomposers. Primary consumers are directly dependent on autotrophs (producers), e.g.: Grasshopper, squirrel, elephant) Secondary consumers use herbivores as their food, e.g.: Frog, owl, fox, etc. Apex or top consumers use herbivores and carnivores as their food. No animals feed on top consumers, e.g.: Tiger, lion, etc. Omnivores feed on herbivores and carnivores, e.g.: Humans, bear, etc. A continuous interaction between producers, consumers and decomposers in a definite sequence is called as food chain. Food chain, in ecology is the sequence of transfers of matter and energy in the form of food from organism to organism. Food chains intertwine locally into a food web because most organisms consume more than one type of animal or plant. Plants, which convert solar energy to food by photosynthesis, are the primary food source. In a predator chain, a plant-eating animal is eaten by a flesh-eating animal. In a parasite chain, a smaller organism consumes part of a larger host and may itself be parasitized by even smaller organisms. In a saprophytic chain, microorganisms live on dead organic matter.
In simple words: A food chain illustrates the linear flow of energy from producers to consumers to decomposers, showing which organism eats another in a definite sequence. Different organisms occupy different trophic levels based on their feeding habits.
🎯 Exam Tip: When explaining a food chain, always define producers, consumers (primary, secondary, apex), and decomposers, and illustrate with clear examples.
Question 2. Energy pyramid
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक जलीय पारिस्थितिकी तंत्र में ऊर्जा के पिरामिड को दर्शाता है। सबसे निचले स्तर पर फाइटोप्लांकटन (10,000 kcal) हैं, जो प्राथमिक उत्पादक हैं। जैसे-जैसे ऊर्जा ऊपरी पोषण स्तरों (ज़ूप्लांकटन, मछलियाँ, मनुष्य) तक पहुँचती है, प्रत्येक स्तर पर ऊर्जा की मात्रा घटती जाती है।
Answer: An energy pyramid is a model that shows the flow of energy from one trophic, or feeding, level to the next in an ecosystem. The model is a diagram that compares the energy used by organisms at each trophic level. The energy in an energy pyramid is measured in units of kilocalories (kcal). Energy pyramids are similar to biomass pyramids, another type of trophic pyramid that models the amount of biomass at each trophic level in an ecosystem, energy flow in ecosystems. The structure of an energy pyramid reflects the trophic structure of an ecosystem.
The pyramid is divided into trophic levels similar to those in a food chain. At the pyramid base are the producers, autotrophic organisms that make their own food from inorganic substances. All of the other organisms in the energy pyramid are consumers. These are heterotrophs, meaning that they get food energy by consuming other organisms. The consumers at each trophic level feed on organisms from the level below and are themselves consumed by organisms at the level above. Primary consumers are organisms that consume producers; thus, most primary consumers are herbivores, though some may be detrivores (organisms that feed on decaying organic matter).
Secondary consumers are carnivores that feed on primary consumers and tertiary consumers are carnivores that eat secondary consumers. In rare instances, an ecosystem may have an additional trophic level composed of quaternary consumers camivores that consume tertiary consumers' energy pyramid. The shape of an energy pyramid shows that the amount of food energy that enters each trophic level is less than the amount that entered the level below.
In simple words: An energy pyramid illustrates how energy decreases significantly at each successive trophic level from producers at the base to apex consumers at the top, typically losing about 90% of energy as heat at each transfer.
🎯 Exam Tip: Remember the 10% rule of energy transfer: only about 10% of the energy from one trophic level is passed on to the next, with the rest lost as heat.
Approximately 90 percent of the food energy that enters a trophic level is "lost" as heat when it is used by organisms to power the normal activities of life such as breathing and digesting food the remaining 10 percent is stored in the various organisms' tissues.
It is this latter energy that is available to be passed to the next trophic level. Thus, the higher the trophic level on the pyramid, the lower the amounts of available energy ecosystem energy transfer through an ecosystem. The number of organisms at each level decreases relative to the level below because there is less energy available to support those organisms. The top level of an energy pyramid has the fewest organisms because it has the least amount of energy. Eventually there is not enough energy left to support another trophic level; thus most ecosystems only have four trophic levels.
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