Table of Contents

A. Tick (✓) the correct option

1. Which one is not a part of biological environment?

✅ (b) water

2. Volcanoes erupt due to—

✅ (a) internal disturbance of the earth

3. Which one brings a sudden change in the environment?

✅ (b) rainfall

4. Identify the term that stands for the topmost layer of the earth comprising loose material—

✅ (b) soil

5. In which year was the Wildlife Protection Act passed in India?

✅ (b) 1972

B. Give a single term for each of the following sentences

A situation or condition in which an organism lives — Environment
The only planet in our solar system where life exists — Earth
The uppermost part of the lithosphere which is rich in silica and aluminium — Sial
The sphere of air that envelopes the earth — Atmosphere
Mass of water on the earth’s surface — Hydrosphere

C. Match the following

Column A	Column B
1. Physical environment includes	(c) Non-living things
2. It is the most dynamic in nature	(a) Atmosphere
3. A narrow zone supporting life	(d) Biosphere
4. They are capable of modifying environment	(b) Human beings
5. Rocks rich in silica and magnesium	(e) Sima

D. Answer the following questions in brief

1. Name the major components of the environment.

The environment is mainly divided into two major components:

(i) Physical Environment

It includes all non-living things around us such as:

land
water
air
soil
mountains
climate

These provide the basic conditions necessary for life.

(ii) Biological Environment

It includes all living organisms such as:

plants
animals
human beings
microorganisms

Both physical and biological environments are closely related and depend upon each other.

2. What is meant by Sima and Sial?

The earth’s crust is mainly made up of two layers called Sial and Sima.

Sial

It is the upper layer of the earth’s crust.
It is mainly made up of silica and aluminium.
Continental regions are mostly composed of sial.

Sima

It lies below the sial layer.
It is mainly made up of silica and magnesium.
Ocean floors are mostly made of sima.

These layers form important parts of the lithosphere.

3. Mention the distribution of water in the Northern and Southern hemispheres.

The distribution of water is unequal in the two hemispheres of the earth.

Northern Hemisphere

Contains more land area and less water.
About 60% land and 40% water.

Southern Hemisphere

Contains more water and less land.
About 80% water and 20% land.

Because of the large amount of water, the Southern Hemisphere is sometimes called the “Water Hemisphere”.

4. Give the literal meaning of four spheres of environment.

The environment is divided into four major spheres. Their literal meanings are:

Sphere	Literal Meaning
Lithosphere	Sphere of land
Hydrosphere	Sphere of water
Atmosphere	Sphere of air
Biosphere	Sphere of life

Together, these spheres make life possible on Earth.

5. What is the atmosphere composed of?

The atmosphere is made up of a mixture of gases, water vapour and dust particles.

Main gases present in the atmosphere:

Nitrogen — about 78%
Oxygen — about 21%
Other gases like carbon dioxide, argon and helium — about 1%

Importance of atmosphere:

Provides oxygen for breathing
Protects the earth from harmful rays of the sun
Helps in weather formation and rainfall
Maintains suitable temperature for life

Thus, the atmosphere is very important for all living organisms.

E. Answer the following questions

1. Differentiate between the physical and the biological environment.

Physical Environment	Biological Environment
Includes non-living things	Includes living things
Consists of land, water, air and soil	Consists of plants, animals and human beings
Does not grow or reproduce	Living organisms grow and reproduce
Provides basic conditions for life	Depends on the physical environment for survival

Explanation:

The physical environment forms the natural surroundings, while the biological environment includes all forms of life living within those surroundings.

2. Why is the earth called the ‘Blue Planet’?

The earth is called the “Blue Planet” because about 71% of its surface is covered with water.

When viewed from space, the large oceans and seas make the earth appear blue in colour.

Water is very important for life, and the abundance of water makes Earth unique among known planets.

3. Define biosphere. Why is it important for us?

The biosphere is the narrow zone of the earth where land, water and air interact to support life.

It includes all living organisms such as:

plants
animals
human beings
microorganisms

Importance of biosphere:

It supports life on Earth.
It provides food, oxygen and natural resources.
It maintains ecological balance.
It connects living organisms with land, water and air.

Without the biosphere, life on Earth would not be possible.

4. Explain with the help of an example how physical and biological components of the environment are interdependent.

Physical and biological components depend on each other for survival and balance in nature.

Example:

Plants need:

sunlight,
air,
water,
and soil

to prepare food and grow.

Animals and humans depend on plants for:

food,
oxygen,
shelter,
and many other needs.

At the same time, plants also benefit from animals and humans through carbon dioxide and nutrients returned to the soil.

Thus, living and non-living components work together and are interdependent.

5. Explain two ways in which human beings are disturbing the natural environment.

Human activities are causing serious harm to the environment in many ways.

(i) Deforestation

People cut forests for agriculture, industries and buildings.

Effects:

loss of wildlife
soil erosion
decrease in rainfall
increase in pollution

(ii) Pollution

Factories, vehicles and human waste pollute air, water and land.