Chapter 14: Our Environment

Internal Questions and Answers

1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

Answer: Trophic levels represent the different positions or levels within a food chain, indicating the flow of energy and nutrients in an ecosystem. Each trophic level represents a group of organisms that occupy a specific position in the food chain based on their source of energy and feeding habits.

Example of a food chain:

 Grass → Grasshopper → Frog → Snake → Hawk

Trophic levels in this food chain:

(i) Primary Producer: Grass (autotroph, produces its own food through photosynthesis)

(ii) Primary Consumer: Grasshopper (herbivore, feeds on grass)

(iii) Secondary Consumer: Frog (carnivore, feeds on grasshoppers)

(iv) Tertiary Consumer: Snake (carnivore, feeds on frogs)

(v) Quaternary Consumer: Hawk (apex predator, feeds on snakes)

2. What is the role of decomposers in the ecosystem?

Answer: Decomposers play a crucial role in the ecosystem by breaking down organic matter, such as dead plants and animals, into simpler substances. They recycle nutrients back into the environment, facilitating the nutrient cycle and enabling the reuse of organic materials by other organisms.

Internal Questions and Answers :

1. Why are some substances biodegradable and some non-biodegradable?

Answer: The biodegradability of substances depends on their chemical composition and structure. Biodegradable substances are typically organic compounds that can be broken down by natural processes, such as the action of microorganisms. Non-biodegradable substances often have complex or stable structures that resist decomposition by natural processes, leading to their persistence in the environment.

2. Give any two ways in which biodegradable substances would affect the environment.

Answer: Two ways in which biodegradable substances can affect the environment are:

(i) Nutrient Recycling: Biodegradable substances, when decomposed by microorganisms, release nutrients into the environment, contributing to the natural nutrient cycles and supporting the growth of plants and organisms.

(ii) Pollution Reduction: Proper disposal or decomposition of biodegradable substances helps reduce pollution, as they break down into harmless compounds without leaving a long-lasting environmental impact.

3. Give any two ways in which non-biodegradable substances would affect the environment.

Answer: Two ways in which non-biodegradable substances can affect the environment are:

(i) Environmental Accumulation: Non-biodegradable substances, such as plastic, can accumulate in the environment and persist for long periods, leading to pollution of land, water bodies, and ecosystems.

(ii) Wildlife and Marine Life Impacts: Animals may ingest or get entangled in non-biodegradable materials, causing harm or even death. Marine life can be particularly affected by plastic pollution, disrupting ecosystems and endangering species.

Internal Questions and Answers

1. What is ozone and how does it affect any ecosystem?

Answer: Ozone is a gas made up of three oxygen molecules (). In the Earth's atmosphere, it forms a protective layer called the ozone layer. This layer shields the planet from harmful ultraviolet (UV) radiation. Ozone depletion can lead to increased UV radiation reaching the Earth's surface, causing various impacts on ecosystems, such as harm to plant life, marine organisms, and the overall balance of ecosystems.

2. How can you help in reducing the problem of waste disposal? Give any two methods.

Answer: Individuals can contribute to reducing waste disposal problems through the following methods:

(i) Recycling: Separating recyclable materials like paper, plastic, glass, and metal from regular waste and ensuring they are sent for recycling. This reduces the volume of waste going to landfills and conserves resources.

(ii) Composting: Composting organic waste, such as food scraps and yard waste, to create nutrient-rich compost that can be used for gardening. This diverts organic waste from landfills and reduces methane emissions.

Exercise 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) Grass, flowers and leather

 (c) Fruit-peels, cake and lime-juice

(d) Cake, wood and grass

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

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 .

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 disrupt the entire food chain or web. The loss of one trophic level can lead to a cascading effect, causing imbalances in the population dynamics of other trophic levels and potentially affecting the overall stability and functioning of the ecosystem.

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 can vary depending on the specific ecosystem and the interconnectedness of the trophic levels. However, removing organisms from any trophic level can have repercussions throughout the food chain, disrupting energy flow, nutrient cycling, and species interactions. Each trophic level contributes to the overall balance and functioning of the ecosystem, making their removal detrimental to the ecosystem's health.

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

Answer: Biological magnification is the increase in concentration of harmful chemicals (like pesticides) in organisms at each successive trophic level of a food chain.

Yes, the level is different at each level. It goes on increasing from producers to top consumers, because these substances are not broken down and keep accumulating in the bodies of organisms.

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

Answer: Non-biodegradable wastes pose several problems, including:

(i) Environmental Pollution: They contribute to land, water, and air pollution, affecting ecosystems and wildlife.

(ii) Accumulation: Non-biodegradable wastes do not break down naturally, leading to the accumulation of waste in landfills, oceans, and other areas.

(iii) Health Risks: Improper disposal or management can pose health risks to humans and animals through contamination and exposure to hazardous substances.

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

Answer: No, even if all waste is biodegradable, it will still affect the environment. Large amounts of biodegradable waste can produce foul smell and release harmful gases like methane during decomposition. This can pollute air and disturb the balance of ecosystems. Also, excessive waste can overload natural decomposition processes, causing environmental problems.

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

Answer:  Damage to the ozone layer is serious because it protects us from harmful ultraviolet (UV) rays of the sun. Without it, UV rays can cause skin cancer, eye damage, and harm plants and marine life.

To limit this damage, use of CFCs has been reduced, eco-friendly alternatives are promoted, and international agreements like the Montreal Protocol have been implemented.