Chapter- 17 Forests - Our Lifeline Class 7th ppt. This Chapter is taken from NCERT Class 7th Science textbook. This ppt is only for Class 7th students.

1. Chapter - 17
Forests : Our Lifeline
Presented by: Swayam R. Khobragade

2. 1) Forest :-
Forest is a natural habitat for many different kinds of plants and
animals. Forests provide food and shelter for animals.
Some common animals found in a forest are :- lion, tiger, elephant,
monkey, deer, zebra, jackal, bison, boar, snake, porcupine, crocodile etc.
Some forest animals

3. ● Some common types of plants found in forests are trees like: teak,
bamboo, fig, saal, sheesham, semal, neem, palash, khair, amla,
kachnar etc. Forests also have several kinds of shrubs, herbs and
grasses, climbers, creepers etc.
Some trees found in the forests.

4. 2) Products we get from forests :-
We get several useful products from forests like wood, spices, gum, oils,
honey, sealing wax, catechu, fodder for animals, medicinal plants etc.
Forest products

5. 3) Characteristics of trees in forests :-
The branchy part of a tree above the stem is called the crown of the
tree. The crown of trees have different shapes.
The branches of tall trees look like a roof over the other plants in the
forest. This is called a canopy.
Trees have different heights, crowns, shapes of leaves, flowers and
fruits.
Some crown shapes of trees.

7. 4) Interdependence of components of forest :-
Forest has different types of plants and animals. They are autotrophs,
heterotrophs, saprotrophs and decomposers.
Autotrophs:- are green plants which prepare food by photosynthesis.
Heterotrophs:- are animals which get their food directly or indirectly from plants.
Saprotrophs:- are animals which feed on dead animals.
Decomposers:- are microorganisms which decompose dead plants and animals
into humus.
Food chain:- Organisms which feed on plants are eaten by other organisms and so
on to form food chains.
Eg : Grass Insects Frog Snake Eagle
There are many food chains in the forest. All food chains are linked together. If any
food chain is disturbed, it affects other food chains.
Every component of forest depends on one another. If we remove one component
like trees, all the other components are affected.
eaten by eaten by eaten by eaten by

8. Interrelationship of plant, soil and decomposers in a forest

9. 5) Balance of oxygen and carbon dioxide in the atmosphere :-
Oxygen During respiration plants and animals take in oxygen and release
carbon dioxide. During photosynthesis plants take in carbon dioxide and
release oxygen. So plants help to maintain the oxygen and carbon dioxide
balance in the atmosphere.
This is why forests are called green lungs.

10. Balance of oxygen and carbon dioxide

11. 6) Importance of forests :-
i) Forest is a natural habitat for a large number of plants and animals.
ii) Forest help in maintaining the oxygen and carbon dioxide balance in the
atm atmosphere.
iii) Forests help in bringing good rainfall.
iv) Forest help to protect soil from erosion.
v) Forest absorb rainwater and helps to maintain water table.
vi) We get medicinal plants, timber and many other useful products from
fore forests.
vii) Many people live in forests and forest provide them with food, water,
shelt shelter and medicines.

12. ★ What would happen if forest disappears?
If forest disappear the following changes occurs:
i) The amount of carbon dioxide in air will increase, resulting in the
solid increase of earth’s temperature.
ii) In the absence of trees and plants, the animals will not get food
and and shelter.
iii) In the absence of trees, the soil will not hold water, which will cause
floods floods.
iv) Deforestation will endanger our life and environment.

13. ❏ Let's Revise
1. We get various products from the forests surrounding us.
2. Forest is a system comprising various plants, animals and microorganisms.
3. In a forest, trees form the uppermost layer, followed by shrubs. The herbs form the
lowest layer of vegetation.
4. Different layers of vegetation provide food and shelter for animals, birds and insects.
5. The various components of the forest are interdependent on one another.
6. The forest keeps on growing and changing, and can regenerate.
7. In the forest, there is interaction between soil, water, air and living organisms.
8. Forests protect the soil from erosion.
9. Soil helps forests to grow and regenerate.
10. Forests are the lifeline for the forest-dwelling communities.
11. Forests influence climate, water cycle and air quality.