CLASS 8 · SCIENCE · CHAPTER 12

How Nature Works in Harmony

Simple answers to the opening prompts, chapter activities, all nine end questions and reflection prompts, and all four projects.

31 worked answersComplete chapter answers

Read the NCERT questions ↗← All chapters

31 worked answers · short steps first, explanations when you need them

Probe and Ponder

Textbook pages 190

Question Opening prompt 1

How can forest loss and changing rainfall lead elephants into farms and villages?

Steps only

Less forest, food, and water can push elephants towards farms and villages.

Answer

Less forest, food, and water can push elephants towards farms and villages.

Question Opening prompt 2

How would a tree interact with water, sunlight, animals, and other parts of a forest?

Steps only

A tree depends on sunlight, water, air, and soil, and provides food and shelter.

Answer

A tree depends on sunlight, water, air, and soil, and provides food and shelter.

Question Opening prompt 3

Can Earth thrive without humans? Can humans survive without Earth?

Steps only

Earth can exist without people; people depend on Earth.

Answer

Earth can exist without people; people depend on Earth.

Question Opening prompt 4

If two kinds of birds compete for the same fruit, how could their ways of living change?

Steps only

They may change where or when they feed, or one population may decline.

Answer

They may change where or when they feed, or one population may decline.

Question Opening prompt 5

Can human actions cause natural disasters?

Steps only

Human actions can worsen some hazards and their impacts, though they do not cause every natural event.

Answer

Human actions can worsen some hazards and their impacts, though they do not cause every natural event.

Question Opening prompt 6

Write a question about how nature works in harmony.

Steps only

Example: How do decomposers return nutrients to soil?

Answer

Example: How do decomposers return nutrients to soil?

Chapter Investigations

Textbook pages 191–207

Question Activity 12.1

What living and non-living components might you record in a pond and a forest?

Steps only

Biotic: plants, animals, microbes. Abiotic: water, air, soil, light, temperature.

Answer

Biotic: plants, animals, microbes. Abiotic: water, air, soil, light, temperature.

Question Activity 12.2

What does a population count show?

Steps only

A population is members of the same kind living in an area at a given time.

Answer

A population is members of the same kind living in an area at a given time.

Question Activity 12.3

Why might a pond with fish have more flowering plants nearby than a pond without fish?

Steps only

Fish may reduce dragonflies, leaving more pollinators to visit nearby flowers.

Answer

Fish may reduce dragonflies, leaving more pollinators to visit nearby flowers.

Question Activity 12.4

Give an example of each: biotic–abiotic, abiotic–abiotic, and biotic–biotic interaction.

Steps only

Earthworm–soil; sunlight–temperature; frog–insect.

Answer

Earthworm–soil; sunlight–temperature; frog–insect.

Question Activity 12.5

How can organisms be classified by how they get food?

Steps only

Producers, herbivores, carnivores, omnivores, and decomposers.

Answer

Producers, herbivores, carnivores, omnivores, and decomposers.

Question Activity 12.6

Make a food chain using grass, grasshopper, frog, snake, and eagle.

Steps only

Grass → grasshopper → frog → snake → eagle.

Answer

Grass → grasshopper → frog → snake → eagle.

Question Activity 12.7

How should millet, mouse, and eagle be placed in a food pyramid?

Steps only

Base: millet; middle: mouse; top: eagle.

Answer

Base: millet; middle: mouse; top: eagle.

Question Activity 12.8

How can a food web be made from a set of organisms?

Steps only

Connect several food chains using arrows from food to eater.

Answer

Connect several food chains using arrows from food to eater.

Question Activity 12.9

What is the difference between mutualism, commensalism, and parasitism?

Steps only

Mutualism: +/+; commensalism: +/0; parasitism: +/−.

Answer

Mutualism: +/+; commensalism: +/0; parasitism: +/−.

Question Activity 12.10

What questions can students ask farmers about their practices?

Steps only

Ask about soil, water, pest control, crop variety, and recycling farm materials.

Answer

Ask about soil, water, pest control, crop variety, and recycling farm materials.

Question Ecosystem concept

How do living and non-living components together make an ecosystem?

Steps only

An ecosystem is a community interacting with its non-living environment.

Answer

An ecosystem is a community interacting with its non-living environment.

Question Decomposition concept

What happens to dead matter in an ecosystem?

Steps only

Decomposers break down waste and return nutrients to soil.

Answer

Decomposers break down waste and return nutrients to soil.

Keep the Curiosity Alive

Textbook pages 207–209

Question 1

Which statement is wrong: (i) community is larger than population; (ii) community is smaller than ecosystem; (iii) ecosystem is part of community?

Steps only

(iii) is wrong: an ecosystem includes a community, not the other way around.

Answer

(iii) is wrong: an ecosystem includes a community, not the other way around.

Question 2

What might happen if decomposers disappeared from a forest?

Steps only

Dead matter would build up and nutrient recycling would slow.

Answer

Dead matter would build up and nutrient recycling would slow.

Question 3

How could mangrove forests reduce damage from a tsunami or strong waves?

Steps only

Mangroves can reduce wave energy and erosion, but cannot prevent all tsunami damage.

Answer

Mangroves can reduce wave energy and erosion, but cannot prevent all tsunami damage.

Question 4

If frogs disappear from grass → grasshopper → frog → snake, what may happen to grasshoppers and snakes?

Steps only

Grasshoppers may increase; snakes may decrease.

Answer

Grasshoppers may increase; snakes may decrease.

Question 5

Why might a school garden have fewer butterflies, and what can students do?

Steps only

Plant native flowers and host plants, and avoid pesticides.

Answer

Plant native flowers and host plants, and avoid pesticides.

Question 6

Why can an ecosystem not work with only producers and no consumers or decomposers?

Steps only

Consumers transfer food energy; decomposers recycle nutrients.

Answer

Consumers transfer food energy; decomposers recycle nutrients.

Question 7

How can two nearby places, such as a park and roadside, be compared as ecosystems?

Steps only

Make two lists and compare living things and physical conditions.

Answer

Make two lists and compare living things and physical conditions.

Question 8

Why are human-made ecosystems such as farms necessary but need to be sustainable?

Steps only

Farms feed people, and sustainable methods protect soil, water, and wildlife.

Answer

Farms feed people, and sustainable methods protect soil, water, and wildlife.

Question 9

If hare numbers fall in the food web, how could other populations change?

Steps only

Plants may rise; hare-eating predators may fall or switch prey.

Answer

Plants may rise; hare-eating predators may fall or switch prey.

Discover, Design, and Debate

Textbook pages 208–209

Question Project 1

How can a school or park clean-up reduce waste?

Steps only

Sort litter safely, record the common types, and plan ways to reduce them.

Answer

Sort litter safely, record the common types, and plan ways to reduce them.

Question Project 2

How can you research an Indian community’s connection with an animal?

Steps only

Research a specific tradition respectfully and verify it with reliable sources.

Answer

Research a specific tradition respectfully and verify it with reliable sources.

Question Project 3

How can you record changes in a tree over four weeks?

Steps only

Make four weekly observations and compare them.

Answer

Make four weekly observations and compare them.

Question Project 4

What can students do to create a sustainable garden or farm?

Steps only

Use local plants, compost, water carefully, and protect soil and useful insects.

Answer

Use local plants, compost, water carefully, and protect soil and useful insects.