Class 10 Biology - Our Environment - Exercises

Questions and Answers

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). Plastic in group (b) is non-biodegradable.

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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.

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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 above

Answer: (d) All of the above.

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4. What will happen if we kill all the organisms in one trophic level?

Answer: If all the organisms in one trophic level are killed, it will cause a major disruption in the ecosystem:

1. Energy Flow: The transfer of energy and matter to the next trophic level will stop.
2. Overpopulation: The population of organisms in the previous trophic level will increase uncontrollably because there are no predators to keep them in check.
3. Starvation: The organisms in the higher trophic level will die of starvation as their food source is eliminated.
4. Ecological Imbalance: The entire food web will be disturbed, leading to a collapse of the ecosystem.

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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:

• Different Impact: Yes, the impact is different for different levels. For example, removing producers (the base of the food chain) is much more catastrophic than removing top carnivores, as producers provide energy for all other levels.
• Damage to Ecosystem: No, organisms of any trophic level cannot be removed without causing damage. Every organism plays a role in maintaining the balance of the ecosystem. Removing even one level leads to an imbalance in the predator-prey relationship and energy flow.

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6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer:

• Biological Magnification: It is the process by which the concentration of harmful, non-biodegradable chemicals (like pesticides and heavy metals) increases at each successive trophic level of a food chain.
• Different Levels: Yes, the levels of magnification are different at different trophic levels. The concentration of these chemicals is lowest in producers and highest in the top-level consumers (like humans), as they consume many organisms from the lower levels, accumulating all the toxins they contained.

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7. What are the problems caused by the non-biodegradable wastes that we generate?

Answer: Non-biodegradable wastes cause several environmental problems:

1. Pollution: They persist in the environment for a long time, polluting soil, water bodies, and air (if burnt).
2. Harm to Wildlife: Animals like cows may ingest plastic bags, leading to choking and death. Aquatic animals can get entangled in or ingest plastic waste.
3. Clogging: They clog drains and sewage systems, leading to waterlogging.
4. Soil Quality: They reduce soil fertility by blocking the passage of air and water into the soil.
5. Toxic Leaching: Some non-biodegradable items like batteries and e-waste leach toxic chemicals into the groundwater.

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8. If all the waste we generate is biodegradable, will this have no impact on the environment?

Answer: Even if all waste were biodegradable, it would still have an impact if not managed properly:

1. Foul Smell: Decomposition of large amounts of organic waste produces a foul smell.
2. Health Hazards: It can become a breeding ground for flies, mosquitoes, and other disease-causing germs.
3. Eutrophication: If large amounts of organic waste enter water bodies, it can lead to oxygen depletion and kill aquatic life. However, the impact would be temporary and manageable compared to non-biodegradable waste, which persists for centuries.

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9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Answer:

• Cause for Concern: The ozone layer protects the Earth from harmful ultraviolet (UV) radiation from the Sun. Damage to this layer allows more UV radiation to reach the Earth, which can cause skin cancer, cataracts, damage to the immune system, and harm to plants and aquatic life.
• Steps Taken:
  1. International Agreements: The Montreal Protocol (1987) was signed to phase out the production and consumption of ozone-depleting substances (ODS) like Chlorofluorocarbons (CFCs).
  2. CFC Substitutes: Industries are now using Hydrofluorocarbons (HFCs) and other alternatives that do not damage the ozone layer.
  3. Awareness: Programs to reduce the use of aerosol sprays and refrigerants containing CFCs.