CBSE – 7th Standard Science

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