CBSE – 7th Standard Science

Chapter 17 – Forests: Our Lifeline

Chapter 17 

Forests: Our Lifeline


  • Forest provides a home for many animals and plants.
  •  Several other trees, shrubs, herbs and grasses are found in the forest.
  • The trees were also covered with different types of creepers and climbers
  • The forest floor provides favorable conditions for seeds to germinate and develop into seedlings
  • The branches of the tall trees look like a roof over the other plants in the forest, it is called a canopy.


  • Branchy part of a tree above the stem is known as the crown of the tree they are of different types and sizes.
  • These had created different horizontal layers in the forest.
  • Giant and tall trees constituted the top layer followed by shrubs and tall grasses, and herbs formed the lowest layer.
  • Every part of the forest is dependent on the other parts.
  • If one component is removed all other components would be affected.


  • The plants help to provide oxygen for animal respiration.
  • They also maintain the balance of oxygen and carbon dioxide in the atmosphere.
  • That is why forests are called lungs.
  • Micro-organisms eat .the dead plant and animal tissues and convert them into a dark coloured substance called humus.



  • The micro-organisms which convert the dead plants and animals to humus are known as decomposers, nutrients of the dead plants and animals are released into the soil.


  • Dead animals become food for vultures, crows, jackals and insects.
  • The decaying animal dung also provides nutrients to the seedlings to grow.
  •  In this way, the  nutrients are cycled. So, nothing goes waste in a forest
  • Trees take in water from their roots and release water vapour into the air through evaporation.
  • Many people also live in the forest.
  • Some of them may belong to different tribes. Depend mostly on the forests.
  • The forest provides them with food, shelter, water and medicines.
  • Larger number of herbivores means increased availability of food for a variety of carnivores.
  • The wide variety of animals helps the forest to regenerate and grow.
  •  Decomposers help in maintaining the supply of nutrients to the growing plants in the forest.
  • Therefore, the forest is a ‘dynamic living entity’   full of life and vitality.”
  • The forest also acts as a natural absorber of rainwater and allows it to seep. It helps maintain the water table throughout the year.
  • Forests not only help in controlling floods but also help maintain the flow of water in the streams so that we get a steady supply of water.,
  •  If trees are not present, rain hits the ground directly and may flood the area around it.
  • Heavy rain may also damages the soil.
  •  Roots of trees normally bind the soil together, but in their absence the soil is washed away or eroded.
  • Forests provide us with oxygen.
  • They protect soil and provide habitat to a large number of animals.
  • Forests help in bringing good rainfall in neighboring areas.
  • We get various products from the forests surrounding us.
  • Forest is a system comprising various plants, animals and micro-organisms.
  • In a forest, trees form the uppermost layer, followed by shrubs.
  • The herbs form the lowest layer of vegetation.
  • Different layers of vegetation provide food and shelter for animals, birds and insects.
  • The various components of the forest are interdependent on one another.
  • The forest keeps on growing and changing, and can regenerate.
  • In the forest, there is interaction between soil, water, air and living organisms.
  • Forests protect the soil from erosion.
  • Soil helps forests to grow and regenerate.
  • Forests are the lifeline for the forest-dwelling communities.
  • Forests influence climate, water cycle and air quality.
  • Cutting of these forests is called as deforestation


  • The effects of deforestation are very large, such as