Extra 20 important long-answer questions with answers for the chapter:13 "Our Environment" from Class 10 CBSE Science:

 

1. What is an ecosystem? Explain its components with examples.

Ans: An ecosystem is a community of living organisms interacting with each other and their physical environment.

Components of an ecosystem:

 

Biotic components (Living organisms):

 

Producers:

Plants, algae (e.g., grass, trees).

Consumers:

Herbivores, carnivores, omnivores (e.g., deer, lion, humans).

Decomposers:

Bacteria, fungi (e.g., mushrooms, earthworms).

Abiotic components (Non-living factors):

 

Air, water, sunlight, soil, temperature.

 

2. What is a food chain? Explain with an example.

Ans: A food chain is the sequence of organisms where energy is transferred by eating and being eaten.

Example:
Grass (Producer) → Grasshopper (Primary consumer) → Frog (Secondary consumer) → Snake (Tertiary consumer) → Hawk (Top consumer).

Importance of food chains:

 

Helps in

energy transfer

.

Maintains

balance in the ecosystem

.

 

3. What is a food web? How is it different from a food chain?

Ans: A food web is a network of interconnected food chains showing multiple feeding relationships.

Differences:

 

Feature	Food Chain	Food Web
Definition	A single sequence of organisms	A network of interconnected chains
Stability	Less stable	More stable
Example	Grass → Deer → Lion	Grass eaten by deer, rabbit, and insect → multiple predators

4. Explain the concept of trophic levels in an ecosystem.

Ans: Trophic levels are the feeding positions in a food chain.

First Trophic Level (Producers):

Plants, algae.

Second Trophic Level (Primary Consumers):

Herbivores (e.g., deer).

Third Trophic Level (Secondary Consumers):

Carnivores (e.g., frog).

Fourth Trophic Level (Tertiary Consumers):

Top predators (e.g., lion).

 

5. What is the 10% Law? Explain with an example.

Ans: The 10% Law states that only 10% of energy is passed from one trophic level to the next.

Example:

If

1000 J

of energy is present in plants, then:

Primary consumer gets 100 J

Secondary consumer gets 10 J

Tertiary consumer gets 1 J

 

6. What is biodegradable and non-biodegradable waste? Give examples.

Ans:

Biodegradable waste

: Can decompose naturally (e.g., paper, food waste).

Non-biodegradable waste

: Cannot decompose easily (e.g., plastic, glass).

 

7. What are the causes and effects of ozone layer depletion?

Ans:
Causes:

CFCs

from refrigerators, ACs, and aerosol sprays.

Industrial pollution

.

Effects:

Increases

UV radiation

, leading to skin cancer.

Reduces

crop production

.

 

8. What are greenhouse gases? Explain the greenhouse effect.

Ans:

Greenhouse gases:

Carbon dioxide (CO₂), Methane (CH₄), Water vapor (H₂O), Nitrous oxide (N₂O).

Greenhouse effect:

Traps heat in the Earth's atmosphere, causing

global warming

.

 

9. What is biomagnification? Explain with an example.

Ans: Biomagnification is the increase in toxin concentration at higher trophic levels.

Example:

Pesticides like

DDT accumulate

in organisms.

A small amount in plants

increases in fish, birds, and humans

.

 

10. Explain the impact of plastic waste on the environment.

Ans:

Non-biodegradable

→ Causes

land & water pollution

.

Harms animals

when ingested.

Clogs drains

, causing floods.

 

11. What is an artificial ecosystem? How does it differ from a natural ecosystem? Explain with examples.

Ans:
An artificial ecosystem is a human-made ecosystem designed for specific purposes.

Differences between Natural and Artificial Ecosystems:

Feature	Natural Ecosystem	Artificial Ecosystem
Definition	Self-sustaining ecosystem formed by nature	Man-made and controlled by humans
Energy Source	Sunlight	Sunlight or artificial sources
Biodiversity	High	Low
Example	Forest, Pond, River	Aquarium, Crop Field, Zoo

Examples of Artificial Ecosystems:

Aquarium:

Requires human intervention for food, oxygen, and cleaning.

Agricultural Fields:

Need fertilizers, irrigation, and pesticides.

 

12. Explain the different types of consumers in an ecosystem with suitable examples.

Ans:
Consumers are organisms that depend on other organisms for food. They are classified into:

Primary Consumers (Herbivores):

Eat only plants.

Examples:

Cow, Deer, Rabbit.

Secondary Consumers (Carnivores):

Eat herbivores.

Examples:

Frog, Snake, Lizard.

Tertiary Consumers (Top Predators):

Eat secondary consumers.

Examples:

Tiger, Eagle, Shark.

Omnivores:

Eat both plants and animals.

Examples:

Humans, Bears, Crows.

Decomposers:

Break down dead organisms.

Examples:

Bacteria, Fungi.

 

13. Explain the impact of human activities on the food chain and food web.

Ans:
Human activities like deforestation, pollution, and overfishing disturb food chains and food webs, leading to ecological imbalance.

Deforestation:

Reduces

producers (plants)

→ Herbivores lose food → Carnivores decline.

Pollution:

Biomagnification

: Accumulation of toxins in top consumers.

Plastic pollution

harms marine life.

Overfishing and Hunting:

Reduces fish populations, affecting aquatic food chains.

Hunting of predators leads to

overpopulation of herbivores

.

Climate Change:

Affects plant growth → Disrupts food availability.

Changes migration patterns of animals.

 

14. What are the causes and effects of eutrophication? How can it be prevented?

Ans:
Eutrophication is the excessive growth of algae in water bodies due to high nutrient levels (nitrates, phosphates) from fertilizers, sewage, and industrial waste.

Causes:

Agricultural runoff

(fertilizers enter rivers and lakes).

Sewage discharge

(organic waste increases nutrients).

Industrial waste

(pollutants promote algae growth).

Effects:

Algal bloom

blocks sunlight → Kills aquatic plants.

Oxygen depletion

(dead algae decay, consuming oxygen).

Loss of biodiversity

(fish die due to lack of oxygen).

Prevention:

Use

organic fertilizers

instead of chemical ones.

Proper

sewage treatment

before disposal.

Reduce

industrial waste dumping

in water bodies.

 

15. Explain the role of decomposers in the ecosystem. What will happen if decomposers are removed?

Ans:
Decomposers (bacteria, fungi, earthworms) break down dead organisms and return nutrients to the soil.

Role of Decomposers:

Convert organic waste into

nutrients

for plants.

Maintain

soil fertility

.

Help in

biogeochemical cycles (carbon, nitrogen cycle)

.

Prevent

accumulation of dead organisms

.

If decomposers are removed:

Dead plants and animals will

pile up

.

Nutrient cycle

will be disrupted → Soil loses fertility.

Food chain will collapse

, affecting all organisms.

 

16. Describe the process of ecological succession and its types.

Ans:
Ecological succession is the gradual change in species composition in an ecosystem over time.

Types of Succession:

Primary Succession:

Occurs in lifeless areas (e.g., volcanic lava, bare rocks).

Pioneer species like

lichens

start the process.

Secondary Succession:

Occurs in areas with

existing soil

but destroyed vegetation (e.g., after a forest fire).

Plants and animals

recolonize

the area.

Importance of Ecological Succession:

Restores

damaged ecosystems

.

Increases

biodiversity

.

Helps maintain

environmental balance

.

 

17. Explain the role of afforestation and reforestation in reducing environmental problems.

Ans:
Afforestation (planting trees in barren land) and reforestation (replanting trees in deforested areas) help in environmental conservation.

Benefits:

Reduces CO₂ levels

→ Slows global warming.

Prevents soil erosion

→ Protects soil fertility.

Enhances biodiversity

→ Provides habitats for wildlife.

Maintains water cycle

→ Increases rainfall.

 

18. How does excessive use of fertilizers affect the environment? What are the alternatives?

Ans:
Excessive use of chemical fertilizers leads to:

Soil degradation:

Kills beneficial microbes.

Water pollution:

Causes

eutrophication

.

Health problems:

Residues in crops can cause diseases.

Alternatives:

Use

organic fertilizers

(compost, manure).

Practice

crop rotation

to maintain soil nutrients.

Use

biofertilizers

(Rhizobium,

Azotobacter

).

 

19. Why is waste segregation important? Explain different types of waste and how they should be disposed of.

Ans:
Waste segregation ensures proper disposal and recycling, reducing pollution.

Types of Waste & Disposal Methods:

Biodegradable waste (food scraps, paper):

Composting.

Non-biodegradable waste (plastic, glass):

Recycling.

E-waste (electronics, batteries):

Special disposal units.

Hazardous waste (chemicals, pesticides):

Safe landfill or incineration.

 

20. How does urbanization affect the environment? Suggest measures to reduce its impact.

Ans:
Urbanization leads to:

Deforestation

(land cleared for buildings).

Air & water pollution

(due to industries and vehicles).

Loss of biodiversity

(wildlife habitats destroyed).

Measures to Reduce Impact:

Green spaces

in cities (parks, gardens).

Public transport

to reduce pollution.

Rainwater harvesting

to save water.

Renewable energy

(solar, wind).