GSEB Class 10 Science Solutions Chapter 15 Our Environment

Question 1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer: The various levels or stages in a food chain where food transfer occurs are called trophic levels. An example of a food chain is: Grass \( \rightarrow \) Grasshopper \( \rightarrow \) Frog \( \rightarrow \) Snake \( \rightarrow \) Peacock.
The different trophic levels in this food chain are:
Grass \( \rightarrow \) Producer \( \rightarrow \) I trophic level.
Grasshopper \( \rightarrow \) I Consumer (Herbivores) \( \rightarrow \) II trophic level.
Frog \( \rightarrow \) II Consumer (Carnivores) \( \rightarrow \) III trophic level.
Snake \( \rightarrow \) III Consumer (Carnivores) \( \rightarrow \) IV trophic level.
Peacock \( \rightarrow \) IV Consumer (Carnivores) \( \rightarrow \) V trophic level.
In simple words: Trophic levels are the stages in a food chain where energy moves from one living thing to another. For example, in a food chain from grass to peacock, each step like grass, grasshopper, frog, snake, and peacock represents a different trophic level.

Exam Tip: Clearly define trophic levels and provide a simple, sequential food chain. Correctly identify the role and trophic level for each organism in your example.

Question 2. What is the role of decomposers in the ecosystem?
Answer: Decomposers break down complex organic substances, such as dead bodies of plants and animals, and convert them into simpler inorganic substances. All the elements present in the dead bodies are then released back into nature. Decomposers help maintain the natural balance and play a vital role in the environment.
In simple words: Decomposers break down dead plants and animals into simple parts, returning important materials to the soil. They are essential for keeping nature clean and balanced.

Exam Tip: Emphasize both functions of decomposers: nutrient recycling and maintaining ecosystem balance. Mentioning the breakdown of complex to simple substances is key.

Question 3. Why are some substances biodegradable and some non-biodegradable?
Answer: Substances that can be decomposed and broken down into simpler forms by microorganisms are called biodegradable. These materials are naturally processed and disappear over time. In contrast, substances that cannot be acted upon by microorganisms or broken down into simpler forms are called non-biodegradable substances. These materials persist in the environment for a very long time.
In simple words: Some things break down naturally with help from tiny living things (biodegradable), while others do not (non-biodegradable) and stay in the environment for a long time.

Exam Tip: The key difference between biodegradable and non-biodegradable substances lies in whether microorganisms can break them down. Use clear examples to illustrate each type.

Question 4. Give any two ways in which bio-degradable substances would affect the environment.
Answer: Two ways in which bio-degradable substances would affect the environment are:
• During the decomposition of these substances, a lot of foul smell spreads in the surrounding areas.
• The places where these biodegradable substances are present, especially with some moisture, become breeding grounds for insects like mosquitoes and houseflies. These insects act as vectors, carrying parasites that cause various diseases.
In simple words: Biodegradable waste can make the air smell bad when it breaks down. It also attracts insects like mosquitoes and flies, which can spread illnesses.

Exam Tip: Focus on direct environmental impacts like odor and disease vectors. Link the decomposition process to these effects.

Question 5. Give any two ways in which non-biodegradable substances would affect the environment.
Answer: Two ways in which non-biodegradable substances would affect the environment are:
• These non-biodegradable substances accumulate and do not decompose. As a result, they remain in the ecosystem, causing pollution. They can also choke the systems of many animals, leading to their death.
• Due to their accumulation, these substances cause water and soil pollution. Examples include pesticides, detergents, and polythene.
In simple words: Non-biodegradable items build up and cause pollution because they do not break down. They can harm animals by blocking their systems and pollute both water and soil.

Exam Tip: Highlight accumulation and persistence as key characteristics. Connect these to pollution of various environmental components and harm to living organisms.

Question 6. What is ozone and how does it affect any ecosystem?
Answer: Ozone is an oxygen molecule with three atoms, and its chemical formula is \( O_3 \). Ultraviolet (UV) radiation splits oxygen molecules into free oxygen atoms. These free atoms then combine with other oxygen molecules to form ozone.
\( O_2 \xrightarrow{\text{UV rays}} O + O \)
\( O_2 + O \rightarrow O_3 (\text{Ozone}) \)
Ozone in Ecosystem:
At ground level, ozone is toxic and harmful. However, at higher levels in the atmosphere, it is very beneficial because it protects all living organisms from the sun's damaging UV radiation. It prevents these radiations from reaching the Earth's surface. UV radiation can cause ionizing effects that contribute to skin cancer in humans.
In simple words: Ozone is a special type of oxygen with three atoms that forms when UV light hits oxygen. Close to the ground, it is bad for us, but high in the sky, it protects all living things from harmful sunlight that can cause diseases like skin cancer.

Exam Tip: Clearly state ozone's composition and formation process. Differentiate its impact at ground level (pollutant) versus in the stratosphere (protective shield), emphasizing its role in blocking harmful UV radiation.

Question 7. How can you help in reducing the problem of waste disposal? Give any two methods.
Answer: To help reduce the problem of waste disposal, we can use the following methods:
• Segregate biodegradable waste from non-biodegradable waste before disposing of it.
• Remove all materials that can be recycled and send them for recycling. Examples include paper, glass, metal, and rubber.
In simple words: We can lessen waste problems by separating trash that breaks down from trash that does not. Also, we should take all items that can be recycled, like paper or glass, to be reused.

Exam Tip: Focus on practical, actionable steps for waste reduction. Segregation and recycling are fundamental concepts to mention.

Activity 15.1 Design aquarium:
Answer:
• Things needed for setting up an aquarium include a large glass jar, water, oxygen, food, and algae.
• We can supply oxygen using an oxygen pump (aerator) and provide fish food bought from the market.
• By adding a few aquatic plants and animals, it can become a self-sustaining system.
• An aquarium is a self-sustaining, human-made ecosystem.
• The aquarium cannot be left as it is; it needs to be cleaned regularly.
We do not need to clean ponds or lakes in the same way because they contain decomposers. These decomposers break down complex organic substances into simple inorganic substances, effectively self-cleaning the natural water bodies.
In simple words: To make an aquarium, you need a glass jar, water, oxygen, food, and algae. You add plants and animals to make it a self-cleaning mini-ecosystem, but it still needs occasional cleaning. Natural ponds and lakes clean themselves because they have decomposers.

Exam Tip: When describing an aquarium, highlight the balance of components and the need for human intervention. Contrast this with natural ecosystems' self-sustaining mechanisms, like decomposers.

Activity 15.2
Answer: While setting up an aquarium, care should be taken not to include any aquatic animals that would eat others. If kept together, all small animals would be eaten by larger ones.
In Pond/Lakes/River.
Green algae/Plants \( \rightarrow \) Small fish \( \rightarrow \) Big fish
Producers \( \rightarrow \) Primary consumers \( \rightarrow \) Secondary consumers
Yes, the producers are of primary importance because they are the ultimate producers for all trophic levels.
In simple words: When building an aquarium, avoid putting animals that eat each other together, as bigger animals will consume smaller ones. Producers like green algae are essential in any ecosystem as they create food for everyone else.

Exam Tip: For ecosystem examples, always identify producers and consumers. Emphasize the critical role of producers as the foundation of any food chain.

Activity 15.3
Answer:
• Pesticides sprayed on farms to protect crops from pests enter the grains. When consumers at one trophic level eat these grains, the pesticides accumulate and are passed on to higher organisms in the food chain.
• To reduce pesticide intake, we must use pesticides carefully on crop plants. We should also use alternative biological methods to control pests.
In simple words: Pesticides on crops get into the food chain and build up in animals at higher levels. To use less pesticide, we should apply them carefully and try other natural ways to control pests.

Exam Tip: Discuss both the problem (pesticide accumulation in the food chain) and the solutions (judicious use and biological pest control). This shows a complete understanding of the issue.

Activity 15.4
Answer: The chemicals responsible for ozone layer depletion are CFCs (Chlorofluorocarbons). The regulations implemented to control the emission of these chemicals have successfully reduced damage to the ozone layer. The size of the ozone layer has shown signs of reduction in recent years.
In simple words: CFCs are chemicals that harm the ozone layer. Rules to stop CFC release have worked, and the ozone layer has gotten smaller recently, meaning less damage.

Exam Tip: Identify CFCs as the primary culprit for ozone depletion. Mention policy interventions and their positive impact as key elements of the answer.

Activity 15.5
1. Collect waste materials from your homes. This could include all the waste generated during a day, like kitchen waste (spoilt food, vegetable peels, used tea leaves, milk packets and empty cartons) waste paper, empty medicine bottles/strips/bubble packs, old and torn clothes and broken footwear.
2. Bury this material in a pit in the school garden or if there is no space available, you can collect the material in an old bucket/flower pot and cover with at least 15 cm of soil.
3. Keep this material moist and observe after every 15 days.

Question a. What are the materials that remain unchanged over long periods of time?
Answer: The materials that stay the same for a long time include empty medicine bottles, bubble wraps, milk cartons, and damaged footwear.
In simple words: Things like empty medicine bottles, bubble wraps, milk cartons, and broken shoes do not change much over a long time.

Exam Tip: When identifying materials that remain unchanged, focus on synthetic or processed items which naturally resist decomposition.

Question b. What are the materials which change their form and structure over time?
Answer: The materials that change their form are rubber, food, vegetable peels, used tea leaves, empty cartons, waste paper, old and torn clothes, and broken footwear if made of leather.
In simple words: Items like rubber, food scraps, vegetable skins, used tea leaves, paper, old clothes, and leather footwear will break down and change over time.

Exam Tip: Think about organic materials and natural fibers when listing items that decompose. Note that some items like footwear can be either, depending on material.

Question c. Of these materials that are changed, which ones change the fastest?
Answer: Among the materials that change, vegetable peels, used tea leaves, and spoiled food break down the fastest.
In simple words: Vegetable skins, used tea leaves, and bad food change and disappear quickest.

Exam Tip: Generally, fresh organic matter decomposes more rapidly due to higher water content and readily available nutrients for microorganisms.

Activity 15.6
Answer:
• Substances that are broken down by biological processes are called biodegradable. For instance, kitchen waste, vegetables, and fruit waste are examples.
• Substances that cannot be broken down by biological processes are called non-biodegradable. For example, plastic bottles and polythene bags.
In simple words: Biodegradable things can be broken down naturally, like food waste. Non-biodegradable things cannot, like plastic bottles.

Exam Tip: Ensure you define both terms clearly and provide distinct examples for each. The ability of biological processes to break down the material is the key differentiator.

Activity 15.7
Answer:
1. Waste generated at home is collected and then placed in a garbage house. Here, biodegradable and non-biodegradable materials are separated. All recyclable substances are segregated and sent for recycling. Those substances that cannot be recycled are kept in the garbage house for disposal.
2. Municipal corporations handle this waste by collecting it and sending it for recycling. They also decompose biodegradable waste and use landfilling for non-recyclable and non-biodegradable waste items. (All research work at class and home levels will be done by the student to find the answers.)
3. Activities 15.8 and 15.9 involve students carrying out research, both in class and at home, to discover the required answers.
In simple words: At home, we sort waste into recyclable, biodegradable, and non-biodegradable items. City councils collect this waste, sending what's reusable to recycling and what breaks down to composting, with the rest going to landfills. Students need to do their own research for activities 15.8 and 15.9.

Exam Tip: For waste management, emphasize the importance of segregation, recycling, and landfilling. Recognize activities requiring student research and state that fact clearly.

Gujarat Board Class 10 Science Our Environment Textbook Questions and Answers

Question 1. Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Answer: (a), (c) and (d)
In simple words: The groups containing only biodegradable items are (a) grass, flowers, and leather; (c) fruit-peels, cake, and lime-juice; and (d) cake, wood, and grass.

Exam Tip: To identify biodegradable items, think about materials that come from living organisms and can decompose naturally by microorganisms.

Question 2. Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer: (b) Grass, goat and human
In simple words: The correct food chain shows how energy flows from grass to a goat, and then from the goat to a human.

Exam Tip: A food chain illustrates the feeding relationships where energy is transferred from one organism to another in a specific sequence. Producers are at the base, followed by consumers.

Question 3. Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the options
Answer: (d) All of the options
In simple words: All the listed practices are good for the environment, including using cloth bags, saving electricity, and walking instead of using a scooter.

Exam Tip: Environment-friendly practices generally involve reducing consumption, conserving energy, and minimizing pollution or waste generation.

Question 4. What will happen if we kill all the organisms in one trophic level?
Answer: If all the organisms in one trophic level are removed, then all the organisms at the next trophic level, which depend on them, will die. These higher trophic levels will not get food to eat, and the entire food chain will be disrupted. At the same time, organisms at the lower trophic level will reproduce and their population will increase significantly, thus unbalancing the ecosystem.
In simple words: If all living things at one level of a food chain are killed, animals that eat them will starve and die. Animals they ate will have too many offspring, causing the whole natural system to go out of balance.

Exam Tip: Explain the cascading effects of removing a trophic level. Mention both the impact on dependent levels (starvation) and the level below (overpopulation), leading to ecosystem imbalance.

Question 5. Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Answer: The impact of removing all the organisms in a trophic level will be similar across different levels. If organisms from any trophic level are removed, it will certainly harm the ecosystem. For example, consider the food chain: Grass \( \rightarrow \) Grasshopper \( \rightarrow \) Frog \( \rightarrow \) Snake \( \rightarrow \) Peacock.
If all grasshoppers are killed or removed, frogs will starve, and grass will reproduce in abundance. If snakes are removed, the number of frogs will increase, which will also disrupt the entire ecosystem.
In simple words: Removing any group of animals from a food chain will always harm the ecosystem, no matter which level they are on. For example, if grasshoppers disappear, frogs will starve and grass will grow too much, upsetting the natural balance.

Exam Tip: Emphasize that all trophic levels are interconnected. Use a specific food chain example to illustrate how removing any component leads to imbalance and damage, not just for the immediate predator/prey but for the entire system.

Question 6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer: Pesticides and chemicals are absorbed by plants from the soil and then enter the food chain. Because they are non-biodegradable, these substances accumulate increasingly at each trophic level. As humans occupy the top level of many food chains, the highest concentration of these chemicals is found in our bodies. This process is known as biological magnification.
The level of magnification will vary at different trophic levels. The maximum concentrations will be found at the highest trophic level, while the chemical will be less concentrated at lower trophic levels.
In simple words: Biological magnification means harmful chemicals, like pesticides, build up more and more as they move up the food chain. People, being at the top, end up with the most chemicals in their bodies. The amount of chemicals increases at each step up the food chain.

Exam Tip: Define biological magnification by focusing on the accumulation of non-biodegradable substances. Clearly state that concentration increases with each higher trophic level, with top predators (like humans) having the highest levels.

Question 7. What are the problems caused by the non-biodegradable waste that we generate?
Answer: The problems caused by non-biodegradable waste that we generate include:
• Since non-biodegradable waste cannot be broken down into simpler forms, it keeps accumulating in nature, causing pollution.
• It leads to various diseases.
• It also contributes to biological magnification.
In simple words: Non-biodegradable waste causes problems because it piles up, creating pollution. It can also lead to sickness and increase the concentration of harmful substances in living things.

Exam Tip: List specific problems associated with non-biodegradable waste, focusing on accumulation, pollution, health impacts, and biological magnification.

Question 8. If all the waste we generate is bio-degradable, will this have no impact on the environment?
Answer: If all the waste we generate is biodegradable and is handled in a way that allows it to decompose properly, then it will have no negative impact on the environment.
In simple words: If all our waste could break down naturally and we managed it well, it would not harm the environment.

Exam Tip: Emphasize the condition of proper management for biodegradable waste. Even biodegradable materials can cause issues if not managed correctly (e.g., overwhelming decomposition systems, anaerobic conditions).

Question 9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer: The ozone layer in the stratosphere is extremely helpful in shielding us from harmful UV rays. Without the ozone layer, severe damage to organisms could occur, leading to diseases like skin cancer, cataracts, and reduced crop production. The damage is being limited by UNEP (United Nations Environment Programme), which forged an agreement to freeze CFC production in 1986.
In simple words: Damage to the ozone layer is worrying because it protects us from harmful UV rays that cause skin cancer and other health issues. To fix this, global agreements were made to stop making CFCs, which harm the ozone.

Exam Tip: Explain the importance of the ozone layer (UV protection) and the specific health/environmental consequences of its depletion. Mention the role of international agreements (like UNEP's efforts) in addressing the problem, specifically targeting CFCs (chlorofluorocarbons used as refrigerants and in fire extinguishers).

Gujarat Board Class 10 Science Our Environment Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1. Name any two groups of producers.
Answer: Plants and blue-green algae.
In simple words: Two types of producers are plants and blue-green algae.

Exam Tip: Producers are organisms that create their own food, usually through photosynthesis. Green plants and photosynthetic microorganisms are classic examples.

Question 2. Name two decomposers.
Answer: Bacteria and fungi.
In simple words: Bacteria and fungi are two examples of decomposers.

Exam Tip: Decomposers break down dead organic matter and recycle nutrients. Bacteria and fungi are the most common and vital decomposers in ecosystems.

Question 3. Write the two raw materials for making food, used by living organisms of first tropic level.
Answer: Carbon dioxide (\( CO_2 \)) and Water.
In simple words: First trophic level organisms, like plants, use carbon dioxide and water to make their own food.

Exam Tip: The first trophic level consists of producers (autotrophs). Recall the basic requirements for photosynthesis: carbon dioxide and water.

Question 4. Which component of sunlight is used for the formation of ozone?
Answer: Ultraviolet radiation.
In simple words: Ultraviolet light from the sun helps create ozone.

Exam Tip: Remember that UV radiation is responsible for breaking down oxygen molecules, leading to the formation of ozone in the stratosphere.

Question 5. Name 4 abiotic components of any ecosystem.
Answer: Temperature, rainfall, wind, soil.
In simple words: Four non-living parts of an ecosystem are temperature, rainfall, wind, and soil.

Exam Tip: Abiotic components are the non-living physical and chemical factors in an ecosystem. Think about climate, geological features, and chemical substances.

Question 6. Name two natural ecosystem.
Answer: Pond ecosystem and forest ecosystem.
In simple words: A pond and a forest are two examples of natural ecosystems.

Exam Tip: Natural ecosystems are self-sustaining and not created or significantly modified by humans. They can be aquatic (pond, ocean) or terrestrial (forest, desert).

Question 7. Name two artificial ecosystem.
Answer: Garden and crop-field.
In simple words: A garden and a farm are two man-made ecosystems.

Exam Tip: Artificial ecosystems are human-made or human-managed environments. They often require human input for maintenance, such as gardens or agricultural fields.

Question 8. What are consumers in the food chain?
Answer: Consumers are organisms that obtain food by eating other organisms. They consume food produced either directly from producers or indirectly by feeding on other consumers.
In simple words: Consumers are living things that eat other organisms to get energy. They either eat plants or other animals.

Exam Tip: Define consumers by their inability to produce their own food and their reliance on other organisms for energy. Classify them further into herbivores, carnivores, and omnivores if space permits.

Question 9. Name the natural cleansing agent in an ecosystem.
Answer: Decomposers and scavengers.
In simple words: Decomposers and scavengers naturally clean up an ecosystem.

Exam Tip: Decomposers (like bacteria and fungi) break down dead organic matter, while scavengers (like vultures) consume dead animals, both contributing to natural cleaning and nutrient recycling.

Question 10. Expand UNEP
Answer: United Nations Environment Programme.
In simple words: UNEP stands for United Nations Environment Programme.

Exam Tip: Memorize important acronyms related to environmental organizations, especially those involved in global initiatives.

Question 11. Define biological magnification.
Answer: Biological magnification is the accumulation of chemicals in the bodies of organisms, which becomes more concentrated as it moves up to the topmost trophic level in a food chain.
In simple words: Biological magnification is when chemicals build up in living things, getting stronger at each step up the food chain.

Exam Tip: Focus on the keywords "accumulation" and "increasing concentration" as you move up the trophic levels when defining biological magnification.

Question 12. What is bad Ozone?
Answer: Ozone at ground level is highly poisonous and is known as bad ozone.
In simple words: Ozone found near the ground is harmful and is called bad ozone.

Exam Tip: Differentiate between stratospheric ozone (good ozone) and ground-level ozone (bad ozone). Ground-level ozone is a pollutant that is harmful to health and the environment.

Short Answer Type Questions

Question 1. Why is plastic bag called non-biodegradable while paper is not?
Answer: A plastic bag is considered non-biodegradable because decomposers cannot act upon it, meaning it cannot be broken down into simple components. In contrast, paper is biodegradable as it can be easily broken down by decomposers.
In simple words: Plastic bags cannot be broken down by nature, so they are non-biodegradable. Paper can be broken down by nature, so it is biodegradable.

Exam Tip: The key distinction lies in the ability of decomposers (microorganisms) to break down the material. Plastic's complex chemical structure resists this process.

Question 2. Differentiate between natural and artificial ecosystem.
Answer:
Natural ecosystem:
• This is an ecosystem that occurs naturally.
• Examples: pond, grassland, forest.
Artificial ecosystem:
• These are human-made ecosystems.
• Examples: garden, aquarium, crop-field.
In simple words: Natural ecosystems form on their own, like ponds and forests. Artificial ecosystems are built by people, such as gardens and farms.

Exam Tip: Provide clear definitions and distinct examples for both types of ecosystems. The primary difference is human involvement in their creation and maintenance.

Question 3. Pesticides are useful to farmers yet considered as pollutants. Give reasons.
Answer: Pesticides are useful to farmers because they protect crops from insects and pests. However, they are also considered pollutants for several reasons: these pesticides remain on the crops, enter the food chain, and accumulate in organisms, reaching the topmost trophic level, which can cause diseases. When washed away by rain, they cause water pollution.
In simple words: Pesticides help farmers by killing pests, but they are also bad because they stay on crops, get into the food chain, and can cause sickness in animals and people. Rain also washes them into water, polluting it.

Exam Tip: Explain both the benefit (pest control) and the harmful effects (bioaccumulation, water pollution) of pesticides. This demonstrates a balanced understanding of their dual nature.

Question 4. Describe the ozone layer presence in stratosphere.
Answer: The ozone layer is located in the stratosphere. When ultraviolet radiation acts on oxygen, the oxygen molecules are converted into ozone.
\( O_2 \xrightarrow{\text{UV radiation}} O + O \)
\( O_2 + O \rightarrow O_3 (\text{Ozone}) \)
The ozone layer functions as a protective shield for living beings. It wards off harmful ultraviolet radiations from the sun, preventing them from reaching the Earth.
In simple words: The ozone layer is high up in the sky, in the stratosphere. It forms when UV light turns oxygen into ozone. This ozone layer acts like a shield, blocking dangerous UV rays from the sun that could harm us.

Exam Tip: Describe the location (stratosphere) and formation process of ozone, including the chemical reactions. Highlight its crucial role as a protective barrier against UV radiation.

Question 5. Explain how the energy transfer takes place through a food chain.
Answer: Different levels in the food chain are referred to as trophic levels. Of the energy consumed by an organism at a particular trophic level, 90% is used by that organism for its own metabolic needs, and only the remaining 10% is available for the organisms at the next trophic level. Therefore, very little energy is left for organisms at higher levels.
For example: a green plant generates 100% energy in the form of chemical energy. 90% of this energy is used for its own purposes, and only 10% of the energy is passed to the primary consumer.
Subsequently, the primary consumer also uses 90% of the energy it consumes and transfers 10% to the next level. This means only 1% of the original energy would reach the secondary consumer. Consequently, the tertiary consumer would receive just 0.1% of the energy initially produced by the green plant. This explains why there can typically be only one or two organisms at the top of the food pyramid.
In simple words: Energy moves up the food chain in steps called trophic levels. Each time energy moves from one level to the next, only about 10% of it is transferred; the rest is used up by the organism or lost. This means less and less energy reaches the top, which is why food chains usually do not have many levels.

Exam Tip: Clearly explain the 10% law of energy transfer, providing a numerical example to illustrate the drastic reduction in energy at successive trophic levels. Link this concept to the limited number of trophic levels in a food chain.

Question 6. Discuss the role of UNEP in controlling the level of CFC release.
Answer: In 1987, the UNEP (United Nations Environment Programme) successfully initiated an agreement among various nations to freeze CFC production at 1986 levels. Later, another agreement was signed by different nations to completely phase out CFCs. It is important to note that CFCs are used in refrigerators and aerosol sprays. Due to the combined efforts of the United Nations and various environmentalists, CFC emissions have been brought under some control. To highlight the importance of ozone each year, September 16th is celebrated as Ozone Day.
In simple words: UNEP played a big part in controlling CFCs, which harm the ozone layer. They got countries to agree to stop making CFCs, which are used in things like refrigerators. Thanks to these efforts, CFC levels are now better managed, and we celebrate Ozone Day on September 16th.

Exam Tip: Mention the specific organization (UNEP) and its key actions (agreements to freeze and phase out CFC production). Also, include the awareness aspect, such as Ozone Day, to demonstrate a comprehensive understanding of global efforts.

Question 7. Study the given flow chart and answer the below given questions.
(a) (i) Which form of the Sun’s energy is trapped by the producer?
(ii) Into which energy form is the Sun’s energy converted when it is trapped by the producer?
(b) (i) Calculate X in the flow chart.
(ii) Calculate Y on the flow chart.
(c) Label the above box on flow chart.

Answer:
(a) (i) The producers trap the Sun's energy in the form of light (or solar) energy.
(ii) When the Sun's energy is trapped by the producer, it is changed into chemical energy.
(b) (i) To calculate X, we follow the energy flow:
First Consumer energy = 6000 units.
Energy transferred to Second Consumer (X) from First Consumer = 3000 units.
Energy lost by First Consumer (respiration) = 1800 units.
The energy available to the Second Consumer (X) is not directly calculated by subtracting from the First Consumer. We look at the diagram's structure. The 3000 unit arrow points from the First Consumer to the Second Consumer. The 1800 unit is lost by the First Consumer. The 'X' box is the Second Consumer's trophic level energy.
Based on the consistency of the diagram (50000 - 34000 - 10000 = 6000; 6000 - 3000 - 1800 = 1200), X = 1200 units.
Thus, X = 1200 units.
(ii) Y is the energy transferred from the second consumer to the third consumer, which is labeled as 360 in the flow chart. So, Y = 360 units.
(c) The box refers to the organisms that process the lost energy and recycle nutrients, which are decomposers like bacteria or fungi.
In simple words: Producers capture sunlight as light energy, turning it into chemical energy. For the diagram, X, the second consumer's energy, is 1200 units after accounting for transfers and losses. Y, the energy passed from the second to third consumer, is 360 units. The box describes decomposers like bacteria and fungi.

Exam Tip: When analyzing flow charts, carefully trace the arrows to understand energy transfers and losses at each trophic level. Pay attention to what each number represents (total energy, transferred energy, or lost energy).

Question 8. Today it is very important to conserve our environment and the species. Discuss the need for conserving species.
Answer: Today, it is crucial to conserve our environment and all species. Many species of animals and plants are at risk of extinction due to factors such as habitat destruction, the introduction of other species, international trade, and pollution. The loss of a species also means that its unique genes are lost, which could be important in the future for genetic engineering (e.g., to improve crops) and the creation of useful chemicals, such as medicines. Furthermore, each species plays an important role in a food chain, and its loss could endanger other species within that chain.
In simple words: Saving species and the environment is very important now. Many animals and plants are dying out because their homes are ruined, new species are introduced, or due to pollution. Losing a species also means losing its unique genetic information and its role in the food chain, which can harm other species and future medical or agricultural advancements.

Exam Tip: When discussing species conservation, highlight multiple reasons: ecological balance (food chains), genetic resources (future applications), and aesthetic/ethical values. Mentioning the causes of extinction strengthens your argument.

Question 9. Discuss the need and ways for conserving the habitat for the organisms.
Answer: If habitats are lost, the species living in them also move towards extinction. Habitat destruction poses the greatest danger to the survival of species. A habitat can be conserved by:
• Using laws to protect the habitat.
• Stakeholders playing a vital role in protecting the habitat.
• Reducing or controlling public access to the habitat.
• Controlling factors, such as water drainage and grazing, that might otherwise contribute to habitat destruction.
In simple words: Protecting animal homes is crucial because losing them leads to species extinction. We can save habitats by making protective laws, having key groups help, limiting public entry, and managing things like water and grazing.

Exam Tip: Connect habitat loss directly to species extinction. When outlining conservation methods, include a mix of policy (laws), community involvement (stakeholders), access management, and ecological controls (water/grazing).

Question 10. Why decomposers are necessary in environment?
Answer: Decomposers act on all biodegradable substances and break them down into simple inorganic materials. This process helps maintain the balance of materials in the ecosystem and effectively cleanses the environment.
In simple words: Decomposers are needed in nature because they break down all organic waste into simple parts, helping to keep the environment clean and balanced.

Exam Tip: Emphasize the two main roles of decomposers: nutrient recycling (returning inorganic materials to the ecosystem) and environmental cleansing (breaking down dead organic matter).

Question 11. Give one advantage and one disadvantage of Ozone.
Answer: Advantage of Ozone – When ozone is in the stratosphere, it prevents ultraviolet radiation from reaching the Earth. These UV radiations cause skin cancer and cataracts.
Disadvantage of ozone – At ground level, ozone is a poisonous gas.
In simple words: Ozone is good because it stops harmful UV rays from reaching us, which can cause diseases. However, ozone near the ground is bad because it is a toxic gas.

Exam Tip: Clearly distinguish between the beneficial role of stratospheric ozone (UV protection) and the harmful effects of ground-level ozone (pollutant). Location determines its impact.

Question 12. Give one example of grassland ecosystem and one example of pond ecosystem.
Answer:
• Grassland Ecosystem: Grass \( \rightarrow \) grasshopper \( \rightarrow \) frog \( \rightarrow \) snake \( \rightarrow \) Peacock.
• Pond Ecosystem : Blue - green algae \( \rightarrow \) small fish \( \rightarrow \) big fish \( \rightarrow \) birds
In simple words: In a grassland, grass is eaten by grasshoppers, then frogs, snakes, and peacocks. In a pond, tiny algae are eaten by small fish, then big fish, and finally by birds.

Exam Tip: For ecosystem examples, choose distinct environments (terrestrial and aquatic) and illustrate their respective food chains, clearly identifying producers and consumers.

Question 13. Energy flow in a food chain is unidirectional. Explain.
Answer: The energy from the sun flows into autotrophs and then passes to herbivores and eventually to carnivores. This energy does not revert from autotrophs to the solar input or from herbivores back to autotrophs. Therefore, the flow moves in only one direction.
In simple words: Energy in a food chain only moves one way. It starts with the sun, goes to plants, then to plant-eaters, and finally to meat-eaters, never going backwards.

Exam Tip: Always remember that energy flow in an ecosystem follows a single, non-reversible path, from producers to various consumers.

Question 14. State different types of consumers in an ecosystem.
Answer: In an ecosystem, the consumers include herbivores, carnivores, omnivores, parasites, saprophytes, and decomposers.
In simple words: Different kinds of consumers in an ecosystem include plant-eaters, meat-eaters, those that eat both, parasites, and organisms that feed on dead matter.

Exam Tip: When listing types of consumers, provide a diverse range of examples to demonstrate a comprehensive understanding of trophic levels.

Question 15. Differentiate between biodegradable and non-biodegradable substances.
Answer:
Biodegradable substances: These materials can be broken down by the action of saprotrophs and other agents. Examples include paper and cloth.
Non-biodegradable substances: These materials cannot be broken down by the action of saprotrophs. Examples include glass and plastics.
In simple words: Biodegradable things can be broken down by nature, like paper. Non-biodegradable things cannot, like plastic.

Exam Tip: Clearly define each term and provide distinct examples for both biodegradable and non-biodegradable substances.

Question 16. Define an ecosystem. Explain in detail about its various components.
Answer: An ecosystem is defined as a specific unit or area within an environment where biotic (living) and abiotic (non-living) components interact together to maintain balance in nature. Its various components are:
• Biotic components – These are the living parts, such as producers, consumers, and saprotrophs.
• Abiotic components – These are the non-living parts, including air, water, and sunlight.
In simple words: An ecosystem is a place where living things and non-living things work together to stay balanced. Living parts are plants and animals, while non-living parts are air, water, and sunlight.

Exam Tip: When defining an ecosystem, always include both biotic and abiotic components and explain their interaction to maintain balance.

Question 17. What is a food chain? List its characteristic features.
Answer: A food chain is defined as the process of energy transfer through a series of organisms that fall on successive trophic levels. Its characteristic features include:
• Energy flow is unidirectional: Energy always moves in one direction, from producers to consumers.
• Energy loss at each level: Only about 10% of energy is transferred from one trophic level to the next, with the rest lost as heat.
• Limited number of trophic levels: Most food chains have only 4-5 trophic levels due to significant energy loss.
• Biological magnification: Harmful chemicals can accumulate and increase in concentration at higher trophic levels.
In simple words: A food chain shows how energy moves from one living thing to another, like a chain. Energy only goes one way, and a lot of it is lost at each step. Harmful stuff can also build up more at the top.

Exam Tip: Clearly define a food chain and then list its key features, focusing on energy transfer and its implications.

Question 18. What is biological magnification?
Answer: Biological magnification is the buildup of chemicals in the bodies of organisms, particularly those at the top trophic level. For humans, who often occupy the highest trophic level, the greatest concentration of these chemicals is found in their bodies, which can cause neurological problems by harming the Central Nervous System.
In simple words: Biological magnification is when harmful chemicals, like pesticides, build up more and more as you go up the food chain, causing the most harm to top predators like humans.

Exam Tip: When explaining biological magnification, emphasize the increasing concentration of chemicals at successively higher trophic levels and its potential impact on top consumers.

Question 19. How is ozone layer important to us?
Answer: While ozone is a pollutant at lower atmospheric levels, it is very important in the stratosphere as it shields us from harmful UV rays. This layer protects living organisms from serious damage, such as skin cancer and cataracts.
In simple words: The ozone layer high up in the sky acts like a shield, stopping dangerous sun rays from reaching us and causing harm like skin cancer.

Exam Tip: Differentiate between good ozone (stratospheric) and bad ozone (ground level) when discussing its importance, focusing on its role in blocking UV radiation.

Question 20. What is causing the damage to ozone layer?
Answer: The damage to the ozone layer is mainly caused by CFC (Chlorofluorocarbon) emissions from various industrial activities. These emissions have contributed to global warming and allow a greater portion of UV rays to reach Earth's atmosphere through ozone holes.
In simple words: The ozone layer is getting damaged mostly by chemicals called CFCs, which come from factories. This damage lets in more harmful sun rays.

Exam Tip: Identify chlorofluorocarbons (CFCs) as the primary culprits behind ozone layer depletion and mention their industrial sources.

Question 21. What are the problems caused by the non-biodegradable waste that we generate?
Answer: Non-biodegradable waste does not decompose under the action of bacteria and other microorganisms, leading to several problems:
• When substances like polythene and plastics are buried under soil, they make that area infertile and cause soil pollution.
• These wastes do not burn completely when oxygen is present and release toxic gases, which cause air pollution.
• The substances can be harmful if they accumulate in the food chain, like DDT, due to biomagnification.
In simple words: Non-biodegradable waste, like plastic, doesn't break down. It pollutes soil when buried, releases harmful gases when burned, and can build up in food chains, harming living things.

Exam Tip: List specific problems associated with non-biodegradable waste, categorizing them by environmental impact (soil, air, biomagnification).

Question 22. Why is damage to ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer: Damage to the ozone layer is a serious concern because it stops harmful ultraviolet rays from the sun from reaching Earth's surface. To prevent further depletion, we must reduce the use of CFCs in aerosols and refrigerants and control their release into the atmosphere. Additionally, there should be an emphasis on using eco-friendly methods and properly disposing of toxic materials.
In simple words: Damage to the ozone layer is worrying because it lets in dangerous UV rays. We need to cut down on CFCs from sprays and fridges, release them less, and use environmentally friendly ways to get rid of harmful stuff.

Exam Tip: Explain both the 'why' (consequences of depletion) and the 'what' (mitigation strategies) thoroughly for a complete answer.

Long Answer Type Questions

Question 1. Enlist various categories of consumers giving examples of each.
Answer: The various categories of consumers are:
• Herbivores – These are grass-eating animals, such as deer and rabbits.
• Carnivores – These are flesh-eating animals, like tigers and lions.
• Omnivores – These animals eat both plants and other small animals, for instance, crows and human beings.
• Parasites – These organisms depend on other living organisms and harm them for food, like lice and tapeworms.
• Saprophytes – These organisms depend on dead and decaying matter for their food, for example, fungi and bacteria.
In simple words: Consumers are categorized by what they eat: herbivores eat plants, carnivores eat meat, omnivores eat both, parasites live off others, and saprophytes feed on dead matter.

Exam Tip: For each category of consumer, provide a clear definition and at least two distinct examples to illustrate your understanding.

Question 2. What three informations are obtained from the energy flow diagrams?
Answer: The information we get from energy flow diagrams includes:
(i) The energy flow is unidirectional; it moves from the Sun to autotrophs, then to herbivores, carnivores, and finally to decomposers.
(ii) The flow of energy is about 10%, meaning that 90% of the energy is used by a given level of the food chain for metabolic activities.
(iii) Unwanted chemicals, such as pesticides, accumulate in the highest organism within the food chain.
In simple words: Energy flow diagrams show that energy moves in one direction, about 10% transfers to the next level, and harmful chemicals build up at the top of the food chain.

Exam Tip: When explaining information from energy flow diagrams, focus on the direction of energy, the efficiency of transfer, and the concept of biomagnification.

Question. Why is it necessary to conserve our environment?
Answer: Conserving our environment is vital because it sustains all life forms, provides essential resources, and helps maintain ecological balance. Without conservation, we risk depleting resources, increasing pollution, and losing biodiversity, which ultimately harms human well-being.
In simple words: We need to save our environment because it gives us everything we need to live and keeps nature balanced. If we don't, we'll run out of resources and face more pollution.

Exam Tip: Highlight the interconnectedness of environmental health with human survival and resource availability when discussing the need for conservation.

Question. State the importance of green and blue dustbins in the safe disposal of the household waste.
Answer: Green and blue dustbins are important for the safe disposal of household waste by facilitating segregation at the source. Green bins are typically for biodegradable waste (like kitchen scraps), allowing for composting, while blue bins are for non-biodegradable, recyclable waste (like plastic, paper, metal), which can then be processed efficiently. This separation reduces landfill volume and promotes recycling.
In simple words: Green and blue dustbins help us sort trash. Green is for food waste that can rot, and blue is for things we can recycle, like plastic. This helps keep our environment clean.

Exam Tip: Explain how color-coded dustbins aid in waste segregation, which is a crucial first step in effective waste management and recycling.

Question. List two values exhibited by your classmate who is an active member of Eco-club of your school.
Answer: Two values exhibited by a classmate who is an active member of the Eco-club are environmental responsibility and proactive engagement. They demonstrate responsibility by participating in eco-friendly activities and show proactive engagement by initiating or contributing to conservation efforts.
In simple words: A classmate in the Eco-club shows they care about the environment and are good at taking action to protect it.

Exam Tip: When describing values, use positive character traits that directly relate to environmental stewardship and active participation.

Question 3. Explain the interlink of biotic and abiotic factors in any ecosystem.
Answer: In an ecosystem, biotic (living) and abiotic (non-living) factors are interdependent and closely interlinked. For example, grass in a grassland can grow only if it has soil that holds water, along with sufficient sunlight and proper temperature. These abiotic factors are essential for the growth of the biotic component (grass). In contrast, in a desert, the grass does not grow well because these crucial abiotic factors are not readily available.
In simple words: Living and non-living things in an ecosystem need each other. Like, grass needs soil, water, and sun to grow. Without those non-living things, living things can't thrive.

Exam Tip: Use a clear, relatable example (like grass in a grassland vs. desert) to illustrate the dynamic and essential relationship between biotic and abiotic factors.

Question 4. Explain the formation of ozone layer and its importance.
Answer: Ozone is formed when high-energy ultraviolet (UV) radiations split oxygen molecules (\( O_2 \)) into individual oxygen atoms (\( O \)). These free oxygen atoms then combine with other oxygen molecules to form new molecules with three oxygen atoms, which is called ozone (\( O_3 \)).
\( O_2 \xrightarrow{\text{UV rays}} O + O \)
\( O_2 + O \rightarrow O_3 (\text{Ozone}) \)
Importance of Ozone: The ozone layer in the stratosphere is extremely protective because it prevents harmful ultraviolet radiations from reaching Earth's surface. These UV radiations can cause severe health issues in humans, such as skin cancer and cataracts.
In simple words: The ozone layer is made when strong sunlight breaks oxygen apart, and then the pieces join up to make ozone. It's important because it blocks harmful sun rays that can cause skin cancer and eye problems.

Exam Tip: Describe both the chemical process of ozone formation and its critical role in absorbing harmful UV radiation, ensuring to use correct chemical formulas.

Question 5. What is biological magnification? Explain giving one example.
Answer: Biological magnification is the process where chemicals accumulate in the bodies of organisms, with the highest concentration found in the top organism of a trophic level or food chain.
Example: A farmer sprays pesticides on crops. These pesticides enter the food chain when organisms feed on the crops.
Grass \( \rightarrow \) Grasshopper \( \rightarrow \) Frog \( \rightarrow \) Snake \( \rightarrow \) Hawk
In this food chain, the maximum amount of pesticide will be found in the hawk, which is the top organism, because the chemical keeps accumulating as it moves up each level.
In simple words: Biological magnification means harmful chemicals build up more and more as they go up the food chain. For example, pesticides sprayed on grass become most concentrated in the hawk that eats the snake, which ate the frog, which ate the grasshopper.

Exam Tip: Define biological magnification clearly and provide a sequential food chain example to illustrate how toxins become more concentrated at higher trophic levels.

Question 6. What are decomposers? How are they important for the ecosystem?
Answer: Decomposers are organisms that break down the bodies of dead organisms, releasing all their elements back into nature. They act as natural cleansing agents, making them vital for the ecosystem.
In simple words: Decomposers are like nature's clean-up crew; they break down dead plants and animals and put nutrients back into the soil, keeping the ecosystem healthy.

Exam Tip: Explain the primary function of decomposers (breaking down dead organic matter) and their crucial role in nutrient cycling within an ecosystem.

Question 7. What is the importance of ozone in the environment? Why is it depleting? What precautions are taken to preserve it?
Answer: Ozone is important in the environment because it is present in the stratosphere and protects Earth from harmful ultraviolet radiations. UV rays can cause various diseases in organisms, such as skin cancer and cataracts in human beings.
The ozone layer is depleting due to chlorides and fluorides, which react with ozone molecules and break them down. These chlorides and fluorides are found in CFCs, used in refrigerants and fire extinguishers.
CFC \( \rightarrow \) Chlorofluorocarbon
Precautions taken to preserve the ozone layer include banning the use of CFCs.
In simple words: Ozone in the atmosphere protects us from bad sun rays that cause skin cancer. It's getting smaller because of chemicals like CFCs from fridges. To help, we need to stop using CFCs.

Exam Tip: Address all three parts of the question – importance, causes of depletion, and preservation steps – ensuring a comprehensive response.

Question 8. What are food-chains and food webs? Why are smaller food chains better? What is 10% flow?
Answer:Food chain – A food chain is the flow of food from the sun to autotrophs, then from autotrophs to herbivores, and finally from herbivores to carnivores. A food chain can have two to six levels.
Food web – A food web is formed when an organism is eaten by two or more other kinds of organisms, creating an interlinked chain rather than a straight chain.

Smaller food chains are better because more energy is available for the next level of consumers. Energy loss occurs at each step, and very little energy remains after four trophic levels.
In a terrestrial ecosystem, green plants capture about 1% of the sun's energy and convert it into food energy. When green plants are eaten by primary consumers, a large amount of energy is lost for life processes, and only 10% of the energy is available for the next level of consumers. This is known as the 10% flow rule.
In simple words: A food chain shows how food energy moves from one living thing to another in a line, while a food web shows many connected food chains. Shorter food chains are more efficient because less energy is lost. The 10% rule means only a tenth of the energy from one level passes to the next.

Exam Tip: Define food chains and food webs distinctly. Explain the advantage of shorter chains and clearly describe the 10% energy flow rule.