Page 149 - Health, Population and Environment Education 9

earth from the ultra-violet rays that come from the sun. Plants need carbon dioxide for
preparing food. Air in atmosphere is very important and useful for all the living creatures
living in the earth.
Season change

The earth revolves round the
sun which causes the change
in seasons. The amount of
solar radiation is not even in
all the places on the earth.
It means some parts receive
more amount of solar radiation
while some other parts receive
less amount of it. As a result,
the places receiving more sun
heat have summer season and Fig: 24
the places with less sun heat Season change
have winter season. This also affects the range of temperature, pattern and amount of
precipitation and over all climatic condition of different places. Different types of living
creatures are found in different climatic conditions.
Water
3
About of the total area of the earth is occupied by the water bodies. Water bodies are
4
usually found in low lands and in seas and oceans. Water bodies present on the earth have
made it humid. Water bodies contribute significantly to maintain the mild and moderate
climate which is suitable for living. Water found on the earth is one the reasons for the
existence of different types of living creatures and plants.

Heat and light
Sun is the main source of heat and light on the earth. The heat and light obtained from the
sun is very useful for plants and animals. Plants make food with the help of the sunlight.
Similarly, heat and light help the plants to grow. Heat of the sun is used for generating
solar power. It causes the evaporation process which eventually causes rainfall.

Food
Food is needed by every living thing to survive. Plants prepare their own food by
photosynthesis. Plants provide food to human beings and animals. Herbivorous animals
obtain their food from plants and carnivorous animals obtain their food from other
animals. All these foods for all the living beings are found in nature.

Recycling
Animals and plants living in this earth die ultimately. After they die, they get decayed and
make humus and mix in the top soil. This makes the soil fertile. In fertile soil, plants grow,
bear flowers and fruits which are again consumed by the animals. In this way, the process
of being born and dying has been going on continuously.
GREEN Environment Population and Health Education Book-9 149