Our Environment Exercise Solutions | KalviGavani

I. Choose the Correct Answer (MCQ)

Q1. Identify the fresh water ecosystem

• (a) Pond
• (b) Lake
• (c) River
• (d) All of them ✓

Ponds, lakes, and rivers are all freshwater ecosystems. They contain low salt content and support freshwater organisms like fish, frogs, and aquatic plants.

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Q2. Producers are

• (a) Animals
• (b) Birds
• (c) Plants ✓
• (d) Snakes

Plants are called producers because they produce their own food through photosynthesis using sunlight, water, and carbon dioxide. All other organisms directly or indirectly depend on plants for energy.

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Q3. It is a biodegradable waste

• (a) Plastic
• (b) Coconut Shell ✓
• (c) Glass
• (d) Aluminium

Coconut shells are organic matter that can be broken down by microorganisms over time. Plastic, glass, and aluminium are non-biodegradable — they do not decompose naturally.

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Q4. It is an undesirable change that occurs in air and water

• (a) Recycling
• (b) Reuse
• (c) Pollution ✓
• (d) Reduce

Pollution is the undesirable change in the physical, chemical, or biological characteristics of air, water, or soil that harms living organisms. Recycling, reuse, and reduce are waste management methods — they are solutions, not problems.

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Q5. Usage of chemical pesticides and fertilisers causes ___ pollution

• (a) Air
• (b) Water
• (c) Noise
• (d) None of the above ✓

Chemical pesticides and fertilisers primarily cause land (soil) pollution. When they seep into water bodies they also cause water pollution, but since "land pollution" is not listed among the options, the correct choice is "None of the above."

Exam tip: Some guides mark "Water pollution" as the answer. The textbook states that chemical pesticides and fertilisers cause land/soil pollution. If "land pollution" is an option, choose that. If only air/water/noise are options, pick "None of the above."

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II. Fill in the Blanks

1. Primary consumers that eat plants are called Herbivores.

Herbivores (plant-eaters) occupy the second trophic level in a food chain, right after producers. Examples: deer, rabbit, cow.

2. Temperature, light and wind are Physical (Abiotic) factors.

Abiotic factors are the non-living components of an ecosystem. They are classified into physical factors (temperature, light, wind, rainfall) and chemical factors (oxygen, carbon dioxide, nitrogen).

3. Recycling is the process of converting waste materials into new materials.

Recycling transforms waste into useful products, reducing the need for raw materials. Example: old newspapers are recycled into new paper.

4. Water pollution can spread Diseases and chemicals.

Contaminated water carries disease-causing microorganisms (bacteria, viruses) and harmful chemicals that cause cholera, typhoid, dysentery, and other waterborne diseases.

5. The 3R's are Reduce, Reuse and Recycle.

Reduce — use less; Reuse — use items again; Recycle — convert waste into new products. Reuse means using an item more than once for the same or a different purpose without processing it.

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III. True or False (If False, give the correct statement)

1. The Pacific Ocean is an example of an aquatic ecosystem. — True ✓

The Pacific Ocean is the largest marine (aquatic) ecosystem on Earth. Marine ecosystems include oceans, seas, and coral reefs.

2. Bacteria and fungi are called decomposers. — True ✓

Decomposers break down dead organisms and organic waste into simpler substances, returning nutrients to the soil. Without decomposers, dead matter would accumulate and nutrients would not be recycled.

3. Human and animal wastes are examples of non-biodegradable waste. — False ✗

Correction: Human and animal wastes are examples of biodegradable waste because they decompose naturally through the action of microorganisms like bacteria.

4. Excessive use of pesticides leads to air pollution. — False ✗

Correction: Excessive use of pesticides leads to land (soil) pollution and can also cause water pollution when chemicals leach into water bodies. Pesticides do not primarily cause air pollution.

5. In schools, waste management rules say that we should separate waste into two categories. — True ✓

The two categories are biodegradable waste (food scraps, paper, leaves) and non-biodegradable waste (plastic, glass, metal). Segregation at source makes recycling and disposal easier.

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IV. Match the Following

Explanations:

1. Biotic factor — Animals: Biotic factors are the living components of an ecosystem. Animals are living organisms, hence biotic. 2. Sewage — Water Pollution: Sewage contains harmful waste and pathogens; when discharged into water bodies, it pollutes them. 3. Fertilizers — Land Pollution: Chemical fertilisers alter soil chemistry, reduce soil fertility over time, and cause land/soil pollution. 4. Desert — Terrestrial Ecosystem: Deserts are land-based (terrestrial) ecosystems with low rainfall and extreme temperatures. 5. Smoke — Air Pollution: Smoke from vehicles, factories, and burning waste releases harmful gases and particulate matter into the atmosphere.

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V. Arrange the Following in the Correct Sequence (Food Chains)

A food chain always starts with a producer (plant) and ends with a top carnivore.

Q1. Rabbit → Carrot → Eagle → Snake

Correct sequence: Carrot → Rabbit → Snake → Eagle

Q2. Human → Insect → Algae → Fish

Correct sequence: Algae → Insect → Fish → Human

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VI. Very Short Answers

Q1. Define ecosystem

An ecosystem is a community of living organisms (plants, animals, microbes) interacting with each other and with their non-living physical environment (air, water, soil, sunlight) as a functional unit.

Q2. What are the two types of ecosystems?

The two main types of ecosystems are:

1. Natural ecosystem — formed by nature (e.g., forest, pond, ocean, desert) 2. Artificial ecosystem — created by humans (e.g., garden, aquarium, crop field)

Ecosystems can also be classified as Terrestrial (land-based) and Aquatic (water-based).

Q3. Name two things that can be recycled

1. Paper — old newspapers, notebooks, and cardboard can be recycled into new paper products. 2. Glass — broken glass bottles and jars can be melted and reused.

Other recyclable items: old clothes (can be made into paper), plastics (melted into floor mats, boards), metals (melted and reformed).

Q4. What are the types of pollution?

The four main types of pollution are:

1. Air pollution — caused by smoke, factory emissions, vehicle exhaust 2. Water pollution — caused by sewage, industrial waste, chemical runoff 3. Land (Soil) pollution — caused by fertilizers, pesticides, plastic waste, open dumps 4. Noise pollution — caused by loudspeakers, honking, machinery, fireworks

Q5. Give one example of a food chain in an aquatic ecosystem

Phytoplankton → Small fish → Big fish

Or equivalently: Algae → Aquatic insect → Small fish → Large fish

Phytoplankton/algae are producers; small fish eat them; big fish eat the small fish.

Q6. What are pollutants?

Pollutants are substances that cause undesirable changes in the environment, making air, water, or soil harmful for living organisms.

Examples: sewage, industrial effluents, smoke, vehicular emissions, plastic waste, chemical fertilisers, pesticides, oil spills.

Q7. Identify the type of pollution caused by:

(a) Loud Speaker → Noise pollution

Loudspeakers produce high-decibel sound that disturbs humans and animals, causes hearing damage, sleep disruption, and stress.

(b) Plastic → Land (Soil) pollution

Plastic does not decompose naturally. It accumulates in soil, blocks water seepage, and harms soil organisms.

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VII. Short Answers

Q1. What is biodegradable waste?

Biodegradable waste refers to waste materials that can be broken down and decomposed by natural agents such as microorganisms (bacteria, fungi), oxygen, water, and ultraviolet rays of the sun.

Examples: food waste, paper, cloth, leaves, vegetable peels, coconut shells, human and animal waste.

These wastes decompose naturally and do not persist in the environment for long periods.

Q2. How can we reduce water pollution?

Water pollution can be reduced by the following measures:

• Do not pour leftover cooking oil, old medicines, or waste chemicals down the drain or into water bodies.
• Minimise the use of chemical pesticides and fertilisers in agriculture — they leach into groundwater and nearby water sources.
• Reduce the use of detergents and bleach — they contain harmful chemicals that pollute water.
• Treat industrial waste before discharging it into rivers or lakes.
• Do not litter — always use a waste bin and keep surroundings clean.
• Avoid immersing idols made of toxic materials (chemical-based paints, plaster of Paris) in water bodies.
• Reuse wastewater from washing for home gardening where possible.

Q3. Write the importance of the food chain

The food chain is important because:

1. Shows energy flow: It traces how energy moves from the sun through producers to consumers, showing the sequential relationship of "who eats whom." 2. Maintains ecological balance: Each organism in the chain has a role. Removing any link disrupts the entire ecosystem. 3. Reveals interdependence: It shows how all organisms are connected — changes in one population affect others. 4. Tracks toxic substances: Harmful chemicals like pesticides accumulate at higher trophic levels (biological magnification), which the food chain helps us understand. 5. Nutrient cycling: Decomposers at the end of the chain return nutrients to the soil, enabling producers to grow again.

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VIII. Detailed Answers

Q1. How can you avoid or reduce waste? Give examples.

Avoiding waste means not creating waste in the first place:

• Refuse single-use items — carry your own cloth bag instead of taking a plastic carry bag at the shop.
• Avoid packaged foods — buy fresh fruits and vegetables instead of those wrapped in plastic.
• Say no to use-and-throw products — choose durable, reusable items over disposable ones (e.g., use a steel water bottle instead of buying bottled water).
• Ask yourself "Do I really need this?" before buying something that will be thrown away after one use.

Reducing waste means using less of what you need:

• Write on both sides of paper — this halves your paper consumption.
• Share newspapers and magazines with neighbours instead of buying separate copies.
• Choose durable goods over disposable ones — a sturdy lunch box lasts years; a plastic one breaks quickly.
• Prefer digital communication over printed documents when possible.
• Reuse items creatively — old clothes can become cleaning rags; glass jars can store kitchen items.

Q2. Write a short note on noise pollution

Noise pollution is caused by unwanted, excessive, or disturbing sounds in the environment.

Sources of noise pollution:

• Loudspeakers and public address systems
• Vehicle horns, sirens, and engines
• Construction machinery and factory equipment
• Firecrackers and fireworks
• Loud music from radios, TVs, and concerts

Effects of noise pollution on humans:

• Hearing loss and ear damage from prolonged exposure
• Sleep disturbances leading to fatigue
• Increased stress, anxiety, and high blood pressure
• Difficulty concentrating, especially in children trying to study

Effects on animals:

• Birds in noisy areas must sing louder to communicate, which uses more energy.
• Marine animals like whales rely on sound for navigation; underwater noise from ships disorients them.

How to reduce noise pollution:

• Turn off electronics (TV, music) when not in use.
• Keep TV and music volume at a moderate level.
• Avoid honking unnecessarily; use silencers in vehicles.
• Do not burst firecrackers or use loud fireworks.
• Plant trees around buildings — they act as natural sound barriers.
• Follow noise regulations, especially near hospitals and schools.

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IX. Higher Order Thinking Skills (HOTS)

Q1. What would happen if an organism is removed from a food chain?

Removing any organism from a food chain disrupts the entire chain and causes ecological imbalance.

Example — Grass → Grasshopper → Frog → Snake → Eagle:

If frogs are removed from this chain:

• Grasshoppers lose their predator and their population increases uncontrollably.
• Large numbers of grasshoppers destroy grass and crops (overgrazing).
• Snakes and eagles lose a food source and may starve or move to other areas.
• The entire ecosystem balance is disturbed.

Key principle: Every organism in a food chain has a specific role. Producers capture energy, consumers transfer it, and decomposers recycle nutrients. Removing any link breaks the chain and cascading effects harm the whole ecosystem.

Q2. Explain the link between waste and dangerous diseases like dengue and malaria

Open waste and stagnant water create ideal breeding grounds for mosquitoes:

• Discarded containers, old tyres, coconut shells, and plastic cups collect rainwater.
• Stagnant water in these waste items becomes breeding sites for Aedes mosquitoes (dengue) and Anopheles mosquitoes (malaria).
• These mosquitoes breed, multiply, and spread diseases when they bite humans.

The chain of events: 1. Improper waste disposal → 2. Stagnant water accumulates in waste → 3. Mosquitoes breed → 4. Mosquito bites transmit disease → 5. Dengue / malaria outbreak

Prevention measures:

• Dispose of waste properly in covered bins.
• Do not let water stagnate in containers, flower pots, or tyres.
• Cover water storage containers with lids.
• Keep surroundings clean and dry.
• Use mosquito nets and repellents.

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X. Identify Who Am I?

Q1. "I am the type of pollution caused by burning of fossil fuels like petrol or coal and the smoke of burning garbage."

Burning fossil fuels and garbage releases carbon monoxide, sulphur dioxide, nitrogen oxides, and particulate matter into the atmosphere.

Q2. "I am the type of pollution caused by loud sounds and I can cause serious damage to your ears and also affect sleep."

Loud sounds above 80 dB can cause hearing damage, sleep disturbance, stress, and high blood pressure.

Q3. "I flow from homes and farms into rivers and lakes. I kill fish and make water unfit for drinking."

Sewage from homes and chemical runoff from farms contaminate water bodies, making them unsafe for drinking and harmful to aquatic life.

Q4. "I am the type of pollution caused by using too much chemical fertilizers and pesticides by farmers."

Chemical fertilisers and pesticides alter soil composition, reduce fertility over time, and harm soil microorganisms essential for plant growth.

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XI. Picture-Based Questions

Q1. Explain what is happening in the picture (factory waste entering a river)

The picture shows industrial or domestic waste being discharged into a water body, causing water pollution.

• Factories or homes dump harmful chemicals and sewage directly into rivers or lakes.
• This kills aquatic organisms (fish, plants) by reducing oxygen levels and introducing toxins.
• The water becomes unfit for drinking, bathing, or irrigation.
• People downstream who use this water are at risk of waterborne diseases like cholera and typhoid.

Q2. What types of pollution are caused by open dumps?

Open dumps cause three types of pollution simultaneously:

1. Air pollution: Decomposing waste releases foul-smelling gases (methane, hydrogen sulphide). Burning waste at dumps releases toxic smoke and particulate matter. 2. Water pollution: Rain washes harmful chemicals from the dump into groundwater and nearby water bodies, contaminating drinking water sources. 3. Land (Soil) pollution: Waste degrades soil quality, makes the land unfit for agriculture or habitation, and attracts disease-carrying pests (rats, flies, mosquitoes).

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Activity: Living and Non-Living Things in a Pond

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Activity: Biodegradable vs Non-Biodegradable Waste

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Common Mistakes

1. Confusing biodegradable and non-biodegradable waste. Students often label coconut shells as non-biodegradable. Coconut shells are organic and decompose (slowly) — they are biodegradable. Plastic, glass, and metal are non-biodegradable.

2. Writing "Abiotic" instead of "Physical" for temperature, light, and wind. The textbook distinguishes abiotic factors into physical factors (temperature, light, wind) and chemical factors (oxygen, CO₂, nitrogen). Use "Physical" for the fill-in-the-blank answer.

3. Starting food chains with animals instead of producers. A food chain always begins with a producer (plant/phytoplankton). "Rabbit → Carrot → Snake" is wrong; it must be "Carrot → Rabbit → Snake."

4. Saying pesticides cause air pollution. Chemical pesticides and fertilisers primarily cause land/soil pollution (and secondarily water pollution through runoff). They do not directly cause air pollution.

5. Listing only two types of pollution. There are four types of pollution: air, water, land (soil), and noise. Students often forget noise pollution or land pollution.

6. Confusing natural and artificial ecosystems. Forests, oceans, and deserts are natural ecosystems. Gardens, aquariums, and crop fields are artificial (man-made) ecosystems. Do not mix them up.

7. Writing "Diseases" instead of "Waterborne diseases" for water pollution effects. While "diseases" is acceptable, the precise answer is waterborne diseases (cholera, typhoid, dysentery) — diseases specifically transmitted through contaminated water.

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Exam Checklist

Before your exam, make sure you can:

• [ ] Define ecosystem and list its two types (natural and artificial)
• [ ] Distinguish between biotic and abiotic factors with examples
• [ ] Explain producers, consumers, and decomposers with examples
• [ ] Draw and label at least two food chains correctly (starting with a producer)
• [ ] Differentiate between biodegradable and non-biodegradable waste with 3+ examples each
• [ ] List and explain all four types of pollution (air, water, land, noise) with causes and effects
• [ ] Explain the 3R principle (Reduce, Reuse, Recycle) with examples
• [ ] Describe the impact of noise pollution on humans and animals
• [ ] Explain how waste leads to diseases like dengue and malaria
• [ ] Answer "What happens if an organism is removed from a food chain?"
• [ ] Match pollutants to the type of pollution they cause (sewage → water, smoke → air, etc.)
• [ ] Identify biotic and abiotic components of a pond ecosystem