Case Based Questions: Our Environment | Science Class 10 PDF Download

Q1: Read the source below and answer the questions that follow:

Rohan visited a national park and observed that plants, animals, and microorganisms coexist in a balanced way. His teacher explained that an ecosystem consists of biotic (living) and abiotic (non-living) components that interact with each other to sustain life.

(a) What is an ecosystem? (1 Mark)
(b) Explain the difference between biotic and abiotic components of an ecosystem with examples. (2 Marks)
(c) How is a natural ecosystem different from an artificial ecosystem? (1 Mark) 
OR
(c) Why is an aquarium considered an artificial ecosystem? (1 Mark)

Ans: 
(a) An ecosystem is a system where living organisms interact with their physical environment, maintaining a balance in nature. (1 Mark)
(b) Difference between biotic and abiotic components of an ecosystem is:

• Biotic components: Living organisms like plants, animals, and decomposers.
• Abiotic components: Non-living factors like sunlight, water, air, soil, and temperature.

(c) Difference between Natural ecosystems and Natural ecosystems of an ecosystem is:

• Natural ecosystems (e.g., forests, lakes) function on their own.
• Artificial ecosystems (e.g., aquariums, gardens) need human management.

OR
(c) An aquarium is artificial because it requires human intervention for oxygen supply, food, and waste removal.

Q2: Read the source below and answer the questions that follow:

During a field trip, students observed a deer eating grass and a tiger hunting the deer. Their teacher explained that this is an example of a food chain, where energy flows through different trophic levels.

(a) What is a food chain? (1 Mark)
(b) Explain the different trophic levels in a food chain with an example. (2 Marks)
(c) Why are food chains usually limited to 3-4 trophic levels? (1 Mark) 
OR
(c) How does a food web differ from a food chain? (1 Mark)

Ans:
(a) A food chain is a sequence where one organism eats another, transferring energy from one trophic level to another. (1 Mark)
(b) Example of a terrestrial food chain:

• Producers (T1): Grass (plants that make food).
• Primary consumers (T2): Deer (herbivores that eat plants).
• Secondary consumers (T3): Tiger (carnivores that eat herbivores).

(c) Food chains are limited to 3-4 trophic levels because energy is lost at each level, reducing the amount available for higher organisms.
OR
(c) A food web consists of multiple interconnected food chains, while a food chain is a single pathway of energy transfer. 

Q3: Read the source below and answer the questions that follow:

Newspaper reports showed that fish from a polluted river had high pesticide levels. Scientists explained that harmful chemicals accumulate in organisms through the food chain, a process called biological magnification.

(a) What is biological magnification? (1 Mark)
(b) Explain how harmful chemicals accumulate in organisms through a food chain. (2 Marks)
(c) Why do humans receive the highest amount of toxins in biological magnification? (1 Mark) 
OR
(c) How can we reduce biological magnification? (1 Mark)

Ans: 

(a) Biological magnification is the gradual increase of toxic substances in organisms as they move up the food chain. 
(b) Accumulation of chemicals:

• Pesticides enter water bodies and are absorbed by algae and aquatic plants.
• Small fish eat these plants, accumulating toxins in their bodies.
• Larger fish and humans consume these fish, leading to higher toxin levels in top consumers.

(c) Humans are at the top of the food chain, so they receive the highest concentration of harmful chemicals. 
OR
To reduce biological magnification:

• Use organic farming (reduce pesticide use).
• Proper waste disposal to prevent chemicals from entering water bodies. 

Q4: Read the source below and answer the questions that follow:

A science teacher explained how CFCs (Chlorofluorocarbons) damage the ozone layer, increasing UV radiation exposure. This can cause skin cancer, eye problems, and reduced immunity in humans.

(a) What is the function of the ozone layer in the atmosphere? (1 Mark)
(b) How do CFCs contribute to ozone layer depletion? (2 Marks)
(c) What are the harmful effects of ozone depletion on human health? (1 Mark) 
OR
(c) What steps have been taken to protect the ozone layer? (1 Mark)

Ans:
(a) The ozone layer absorbs harmful UV radiation, protecting living organisms from damage.
(b) Contribution of CFCs

• CFCs released from refrigerators and sprays reach the atmosphere.
• UV radiation breaks down CFCs, releasing chlorine.
• Chlorine reacts with ozone (O₃ → O₂), reducing ozone levels.

(c) Effects of ozone depletion:

• Skin cancer and cataracts due to high UV exposure.
• Weakened immune system in humans.

OR
(c) Steps to protect the ozone layer:

• Banning CFCs (Montreal Protocol).
• Using CFC-free refrigerants and aerosol sprays. 

Q5: Read the source below and answer the questions that follow:

A school conducted an activity where students buried vegetable peels, plastic, and metal cans. After three weeks, they observed that the vegetable peels decomposed, while plastic and metal cans remained unchanged.

(a) What is the difference between biodegradable and non-biodegradable waste? (1 Mark)
(b) How does improper waste disposal affect the environment? (2 Marks)
(c) Why is plastic waste a major environmental problem? (1 Mark) 
OR
(c) Suggest two ways to manage non-biodegradable waste effectively. (1 Mark)

Ans:
(a) Difference between biodegradable and non-biodegradable wasteis  

• Biodegradable waste: Decomposes naturally (e.g., food waste, paper).
• Non-biodegradable waste: Does not decompose easily (e.g., plastic, metal). 

(b) Effects of improper waste disposal:

• Pollution of water and soil due to toxic waste.
• Harm to wildlife when animals ingest plastic.
• Clogging of drains, leading to flooding.

(c) Plastic is a major problem because:

• It is non-biodegradable and lasts for centuries.
• It pollutes oceans and harms marine life.

OR
(c) Ways to manage non-biodegradable waste:

• Reduce, Reuse, Recycle (3Rs).
• Use biodegradable alternatives (e.g., cloth bags instead of plastic bags).

Q6: Read the source below and answer the questions that follow:

Riya visited a pond ecosystem and observed that plants, fish, frogs, and microorganisms were living together. Her teacher explained that in an ecosystem, each organism plays a role, ensuring the flow of energy and nutrients.

(a) What are the two main components of an ecosystem? (1 Mark)
(b) How do decomposers help maintain balance in an ecosystem? (2 Marks)
(c) Why is it important to have producers in an ecosystem? (1 Mark) 
OR
(c) What would happen if all decomposers disappeared from an ecosystem? (1 Mark)

Ans:
(a) Biotic components (living organisms) and abiotic components (non-living factors like water, soil, sunlight).
(b) Decomposers (bacteria, fungi) break down dead plants and animals, returning nutrients to the soil, which helps producers grow.
(c) Producers (plants) make food through photosynthesis, providing energy to all organisms in the ecosystem. 
OR
(c) Without decomposers, waste and dead organisms would accumulate, and nutrient recycling would stop, disrupting the ecosystem.

Q7: Read the source below and answer the questions that follow:

During a science experiment, Aman’s teacher explained that only a small fraction of energy is passed from one trophic level to another, while most of it is lost as heat.

(a) What is meant by the flow of energy in an ecosystem? (1 Mark)
(b) Explain why only 10% of energy is passed to the next trophic level in a food chain. (2 Marks)
(c) Why are there usually only 3-4 trophic levels in a food chain? (1 Mark) 
OR
(c) What happens to the energy that is not transferred to the next trophic level? (1 Mark)

Ans:
(a) Flow of energy is the transfer of energy from producers to consumers through a food chain. 
(b)

• 90% of energy is lost as heat, respiration, and movement.
• Only 10% is stored in the body and passed to the next level.

(c) Energy decreases at each level, so very little is left after 3-4 levels, limiting the number of trophic levels.
OR
(c) The lost energy is used for life processes (respiration, movement) or released as heat into the environment. 

Q8: Read the source below and answer the questions that follow:

A news report stated that plastic pollution is increasing and harming marine life. Scientists warned that non-biodegradable waste is accumulating, affecting ecosystems and human health.

(a) What are non-biodegradable substances? (1 Mark)
(b) How do non-biodegradable substances harm the environment? (2 Marks)
(c) Why should plastic waste be reduced? (1 Mark) 
OR
(c) Suggest two ways to manage non-biodegradable waste. (1 Mark)

Ans:
(a) Non-biodegradable substances do not decompose naturally and persist in the environment for a long time (e.g., plastic, glass).
(b) Harmful effects of non-biodegradable substances: 

• They pollute land and water.
• They harm animals when ingested.
• They cause blockages in drainage systems. 

(c) Plastic waste should be reduced because it pollutes soil and water and takes hundreds of years to decompose.
OR
(c) Ways to manage non-biodegradable waste:

• Recycle and reuse plastic materials.
• Use biodegradable alternatives like paper and cloth bags.

Q9: Read the source below and answer the questions that follow:

A school started a waste segregation program, where students sorted biodegradable and non-biodegradable waste. They also promoted recycling to reduce waste generation.

(a) What is biodegradable waste? (1 Mark)
(b) Why is proper waste segregation important for the environment? (2 Marks)
(c) How does composting help in waste management? (1 Mark) 
OR
(c) Name one biodegradable and one non-biodegradable substance. (1 Mark)

Ans:
(a) Biodegradable waste is waste that naturally decomposes by microorganisms (e.g., food waste, paper). 
(b) Waste segregation:

• Prevents pollution by separating biodegradable and non-biodegradable waste.
• Makes recycling easier.
• Reduces landfill waste.

(c) Composting converts biodegradable waste into nutrient-rich manure, reducing waste and improving soil quality.
OR
(c) Biodegradable: Vegetable peels
Non-biodegradable: Plastic bottle

Q10: Read the source below and answer the questions that follow:

Scientists reported that CFC emissions have decreased due to global efforts, slowing down the ozone layer depletion. However, people must continue using eco-friendly alternatives.

(a) What is the ozone layer, and why is it important? (1 Mark)
(b) How do human activities lead to ozone layer depletion? (2 Marks)
(c) What international agreement was made to reduce ozone depletion? (1 Mark) OR
Suggest two alternatives to CFCs that help protect the ozone layer. (1 Mark)

Ans:
(a) The ozone layer absorbs harmful UV radiation, preventing skin cancer and other health issues. 
(b) Human activities lead to ozone layer depletion are:

• CFCs from refrigerators, ACs, and sprays reach the atmosphere.
• Chlorine from CFCs breaks down ozone (O₃ → O₂), reducing its protective layer. 

(c) The Montreal Protocol (1987) was signed to limit CFC production worldwide. 
OR
(c) Alternatives to CFCs:

• Hydrofluorocarbons (HFCs).
• Eco-friendly refrigerants like ammonia and hydrocarbons.