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Forests Our Lifeline Notes



A forest is an area with a high density of trees. Today, forests occupy approximately one- third of the Earth's land area. Forests are home to many animals and plant species.
There are three major types of forests- tropical, temperate and boreal forests.

Forest profile:

There are different kinds of plants of varied height and size in the forests. Parts of a tree above the stem, including the branches and leaves are collectively known as the Crown. Trees belonging to the genus Pinus have tapered crowns, while a neem tree has a Crown that looks like a globe. Depending on the height of trees and the types of animals that live there, forests are divided into layers.

Emergent layer:
  • The branches on the topmost layer of the tallest trees are known as the emergent layer.
  • This layer is at a height of 40 m from the ground and receives sunlight in abundance.
  • Eagles, butterflies, bats and certain types of monkeys live here.

Canopy layer:
  • Below the emergent layer is the canopy layer.
  • This layer is formed when trees growing close to each other appear as a roof over the rest of the two floors below.
  • This layer is so dense that very little sunlight penetrates it.
  • The canopy measures from about 20m to 40 meters above the ground.
  • It has an abundance of food; hence, it is a dwelling place for many birds, insects and monkeys.

Understorey layer:
  • The space between the canopy and the forest floor is known as the Understorey.
  • This layer of a forest starts from the foot of trees and grows up to 20 metres from the ground. Plants such as orchids, vines, palms and ferns grow in this region.
  • Many birds, insects and a few animals such as leopards and sloth bears live here.

Forest Floor:
  • This is the ground layer of a forest.
  • The soil is moist and water containing decaying leaves, fruits and animal matter.
  • This layer of forests is home to rabbits, snakes, frigs, earthworms, fungi termite and insects.
  • The decomposers (microorganisms) present on the forest floor decompose the dead plant and animal matter to form fertile soil known as humus.

Interdependence of plants and animals in a forest:

  • The plants and animals in a forest depend on each other for their survival. Plants are autotrophs, so also called producers.
  • Living things that eat other organisms as food are called heterotrophs. All animals are heterotrophs, so also called consumers.
  • Some animals eat only plants, such animals are called herbivores.
  • Carnivores animals eat only other animals, whereas omnivorous animals eat both plants and animals.
  • When animals die, their bodies are eaten by crows, vultures and hyenas. This group of animals is called scavengers.
  • The bodies of dead plants and animals get broken down into simpler substances or are decomposed by decomposers like fungi and bacteria present in the soil. The fertility of soil is increased by these decomposers.
  • The energy from the plants enters the consumers in the form of food. This eventually ends up at the decomposers and is released into the soil. This is again used by the plants forming a cycle known as the cycle of nutrients.

Dependence of plants on animals:
Not only do animals depend on plants, but plants also depend on animals in many ways.
Insects and birds feed on the nectar found in the flowers of plants. This helps in the process of pollination of flowers, which leads to the reproduction of plants.
Fruits and seeds, which are produced after pollination, are dispersed by the animals in different places.

Food Chain:
A Food chain is formed when one organism eats another organism for food.
For example, grasshoppers depend on grass and plants for food. Frogs eat the grasshopper. Snakes eat the frogs for their food. This dependence of organisms on one another for food forms a food chain.
A food chain always starts with plants and ends with carnivorous animals. The primary source of energy of all food chains is the sun that provides energy to the plant to make food.


Food Web:
Multiple food chains are interlinked together to form a food web. A food web is an indicator how closely plants and animals of a region depend on each other. If any one member is affected, the entire food web gets disrupted.

Benefits of Forests:

Purification of Air:

Photosynthesis takes place in all kinds of plants, trees and algae in a forest, which releases oxygen that is used by plants and animals for breathing. Animals breathe out carbon dioxide which is used by plants during photosynthesis. So, a balance is formed between the amount of oxygen and carbon dioxide in the air.
Plants and trees in a forest removed excess water through the stomata present on the underside of the leaves. This process is called transpiration, which helps in the water cycle and keeps the atmosphere cool.

Rainfall Due to Forest:

Rainfall is dependent on forests. Excess water from the trees is released in the form of water vapour by the process of transpiration and helps in the formation of Clouds by a process of condensation, which undergoes precipitation to form rain. The absence of forests and trees may lead to floods, soil erosion, depletion in the water table and poor rainfall.

Prevention of Soil Erosion:

Soil erosion is the removal of the top layer of soil. The roots of the trees hold the soil together and help the water to infiltrate into the soil. In this way, soil erosion due to the runoff water and wind is prevented by the forests. Hence, trees act as windbreakers.

Forests- A Source of Wood:

A well-managed forest is a rich source of timber wood and bamboo, which is used for construction houses, making furniture and building ships. Trees such as teak, shisham, rosewood, oak, willow, and sandalwood are sources of wood.

Forests- A Source of Medicinal Plants and Edible Fruits:

A forest is a storehouse of a variety of medicinal plants, some of which do not grow anywhere else. Quinine, a medicine used to treat Malaria is extracted from the bark of the cinchona tree. All parts of the 'trumpet tree' are used to treat respiratory illness while lemongrass is used to treat fever, colds and coughs.

Forests- A Storehouse of Biodiversity:

The variety of living organisms found in a region form the biodiversity of the region. A Forest is a huge storehouse of biodiversity. Some plants and animals are found only in certain forest regions of the world. For example, the golden lion tamarins are found only in some forests of Brazil etc.

Destruction of Forests:

Deforestation is the destruction of large number of trees in a forest and overuse of forest resources
The following are the reasons for deforestation:
  1. Construction of dams, highways and clearing of forest to convert them into cultivable land and other residential areas.
  2. The need for timber and medicinal plants, resulting in illegal logging and smuggling of the precious forest products.
  3. Construction of resorts in and around forests, leading to their destruction.
  4. Lack of awareness in people about the importance of forests.
  5. Overgrazing in forest by cattle from nearby villages.
  6. Poaching and hunting of animals for their meat, skin and bones causing a decrease in the number of animals and disturbance in the food chain.

Consequences of Deforestation:
  1. With no plants and trees to hold the soil together, the soil gets washed away by strong winds and flowing water.
  2. Things like wood, medicine and various other products, which we obtain from forests, would no longer be available.
  3. The most important consequence of deforestation is the change in climate. Without a forest cover, the amount of carbon dioxide will increase in the atmosphere which will cause global warming.
  4. Animals will lose their natural habitat and they might even die. This will eventually lead to extinction of different species.

Conservation of Forests:

  • Steps must be taken to create awareness about the hazards of deforestation and preserving the rich source of forests.
  • Trees should be planted in wastelands where the forest cover is disappearing. The planting of trees in large numbers is called afforestation.
  • People and students should be encouraged to plant more trees through programs like 'Vanmahotsava'.
  • Awareness and education regarding the importance of forest should be given to people and students.
  • Overgrazing by cattle should be prevented by providing sufficient pastures in the areas near forests.
  • Illegal logging of trees for timber must be prevented.
  • Illegal poaching and hunting of animals must be prevented.

Also Read



Reference Books for class 7 Science

Given below are the links of some of the reference books for class 7 math.

  1. Science for Class 7 by Lakhmir Singh
  2. Science Foundation Course For JEE/NEET/NSO/Olympiad - Class 7
  3. CBSE All In One Science Class 7 by Arihant Experts (Author)
  4. IIT Foundation Physics, Chemistry & Maths for Class 7

You can use above books for extra knowledge and practicing different questions.



Class 7 Maths Class 7 Science





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