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13. Our Environment

Long Additional Questions With Solutions

Chapter 13: Our Environment

Long Additional Questions with Solutions

Q1. What is an ecosystem? Describe its components with suitable examples.

Solution:

An ecosystem is a self-sustaining functional unit of nature in which living organisms interact with one another and with the non-living environment.

Components of an Ecosystem:

• Biotic Components: These include all living organisms such as plants, animals, fungi, and microorganisms.
• Abiotic Components: These include non-living factors such as air, water, soil, sunlight, temperature, and minerals.

Example: A pond ecosystem consists of aquatic plants, fish, frogs, insects, bacteria, water, sunlight, and dissolved minerals.

Conclusion: Both biotic and abiotic components work together to maintain ecological balance.

Q2. Explain the structure of a food chain with a suitable example. Why are food chains generally short?

Solution:

A food chain is a sequence of organisms through which food and energy pass from one organism to another.

Example:

Grass → Grasshopper → Frog → Snake → Eagle

• Grass is the producer.
• Grasshopper is the primary consumer.
• Frog is the secondary consumer.
• Snake is the tertiary consumer.
• Eagle is the top consumer.

Food chains are generally short because only about 10% of the energy is transferred from one trophic level to the next, while the remaining energy is lost as heat.

Conclusion: Limited energy transfer restricts the number of trophic levels in a food chain.

Q3. What is a food web? How is it more advantageous than a food chain?

Solution:

A food web is a network of interconnected food chains present in an ecosystem.

Advantages of a Food Web:

• Provides alternative food sources for organisms.
• Maintains ecological balance.
• Increases the stability of an ecosystem.
• Prevents the collapse of the ecosystem if one species disappears.

Conclusion: Food webs are more stable and realistic than single food chains.

Q4. Explain the flow of energy in an ecosystem. State the 10% law with an example.

Solution:

Energy enters an ecosystem through sunlight, which is captured by green plants during photosynthesis. It then passes from producers to consumers through food chains.

10% Law:

According to Lindeman's 10% law, only about 10% of the energy available at one trophic level is transferred to the next trophic level.

Example:

• Producers = 10,000 J
• Primary Consumers = 1,000 J
• Secondary Consumers = 100 J
• Tertiary Consumers = 10 J

Conclusion: Energy flow is unidirectional and decreases at every trophic level.

Q5. What is biological magnification? Explain its harmful effects with an example.

Solution:

Biological magnification is the gradual increase in the concentration of harmful non-biodegradable substances at successive trophic levels of a food chain.

Example:

DDT sprayed on crops enters plants, then insects, fish, birds, and finally humans. Its concentration increases at each trophic level.

Harmful Effects:

• Damage to the nervous system.
• Reproductive disorders.
• Death of birds and aquatic animals.
• Health hazards in humans.

Conclusion: Non-biodegradable pollutants become more harmful at higher trophic levels.

Q6. Differentiate between biodegradable and non-biodegradable substances with suitable examples.

Solution:

Biodegradable Substances	Non-Biodegradable Substances
Can be decomposed by microorganisms.	Cannot be decomposed by microorganisms.
Do not accumulate in the environment.	Remain in the environment for a long time.
Cause less pollution.	Cause long-term pollution.
Examples: Paper, leaves, vegetable peels.	Examples: Plastic, glass, DDT.

Conclusion: Proper disposal of non-biodegradable waste is essential for environmental protection.

Q7. Explain the importance of decomposers in maintaining ecological balance.

Solution:

Decomposers are microorganisms such as bacteria and fungi that feed on dead plants and animals.

Importance:

• Break down dead organic matter.
• Recycle nutrients back into the soil.
• Maintain soil fertility.
• Prevent accumulation of dead organisms.
• Help complete nutrient cycles.

Conclusion: Without decomposers, ecosystems would be filled with dead organic matter and nutrient recycling would stop.

Q8. Explain the causes and harmful effects of ozone layer depletion. How can it be prevented?

Solution:

Causes:

• Release of chlorofluorocarbons (CFCs).
• Industrial emissions.
• Aerosol sprays and refrigerants.

Harmful Effects:

• Increase in harmful UV radiation.
• Skin cancer and cataracts.
• Weakening of the immune system.
• Damage to crops and marine organisms.

Prevention:

• Avoid the use of CFC-based products.
• Use eco-friendly refrigerants.
• Follow international agreements like the Montreal Protocol.

Conclusion: Protecting the ozone layer is essential for the survival of life on Earth.

Q9. Explain the concept of waste management. Discuss the importance of the 3Rs.

Solution:

Waste management involves the proper collection, segregation, recycling, treatment, and disposal of waste.

The 3Rs:

• Reduce: Minimise the use of unnecessary materials.
• Reuse: Use items repeatedly instead of discarding them.
• Recycle: Convert waste materials into useful products.

Importance:

• Reduces pollution.
• Conserves natural resources.
• Saves energy.
• Reduces landfill waste.
• Protects the environment.

Conclusion: Practising the 3Rs helps achieve sustainable development.

Q10. Describe the role of human activities in environmental degradation. Suggest measures for environmental conservation.

Solution:

Human Activities Responsible for Environmental Degradation:

• Deforestation.
• Industrial pollution.
• Excessive use of plastics.
• Overexploitation of natural resources.
• Improper waste disposal.

Measures for Conservation:

• Plant more trees.
• Reduce, Reuse and Recycle waste.
• Use renewable sources of energy.
• Control industrial pollution.
• Create public awareness about environmental protection.

Conclusion: Every individual has a responsibility to conserve the environment and ensure a healthy and sustainable future.