Class 7 Science Our forest Exam Notes

Class 7 Science Our forest Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Covers the following topics:

1.Interdependence of plant & animals

Our Forest is a chapter of the CBSE Class 7 Science syllabus. These exam notes cover the interdependence of plants and animals, how animals depend on plants and plants depend on animals, recycling of nutrients, food chains and food webs, biodiversity in a forest, uses of forests, and conservation of forests.

INTRODUCTION

Forests are one of the most useful renewable resources. They provide habitat to many types of animals and plants. A forest is a biotic community spread over a large area of land, composed of tall trees, herbs, shrubs, climbers and wild animals.

INTERDEPENDENCE OF PLANTS AND ANIMALS

A forest is home to many kinds of plants, animals and microorganisms. These living organisms depend on each other for their survival.

DEPENDENCE OF ANIMALS ON PLANTS

For food: all animals depend, directly or indirectly, on green plants for their food. Herbivores feed on plant material directly, while carnivores feed on herbivores.
For oxygen: plants produce oxygen during photosynthesis, and animals use this oxygen for respiration.
For shelter: some animals depend on plants for shelter and safety. Trees protect animals from rain and shade them from the heat of the sun. Most birds make their nests on the branches of trees. Monkeys, apes and bats also live on trees.

DEPENDENCE OF PLANTS ON ANIMALS

For carbon dioxide: animals produce carbon dioxide during respiration, which is released into the atmosphere. Plants use this carbon dioxide to prepare food by photosynthesis. In this way plants help maintain the balance of carbon dioxide and oxygen in nature.
For pollen and seed dispersal: many insects, birds and bats help in pollination. Some animals help in the dispersal of fruits and seeds.
For supplying nutrients: animal excreta and dead bodies add nutrients to the soil. They act as manure and provide minerals for plant growth.

RECYCLING OF NUTRIENTS IN A FOREST

Plants are called producers because they can produce their own food. They are also called autotrophs. Animals are called consumers because they cannot produce their own food and depend on plants. Animals are also called heterotrophs.
Decomposers are microorganisms that break down the dead remains of plants and animals into simpler substances. They release these nutrients into the soil, water and air.

FOOD CHAIN

The transfer of food from plants through a series of organisms, with repeated eating and being eaten, is called a food chain.
For example, a grasshopper eats a green plant, a frog eats a grasshopper, a snake eats the frog, and an eagle eats the snake.
Plant → Grasshopper → Frog → Snake → Eagle

Food and energy are transferred several times between organisms, but the chain ends with dead animals and plants. The bodies of dead organisms are then broken down into simpler nutrients in the soil by decomposers.

FOOD WEB

All food chains are interlinked. This interconnected network of food chains is called a food web.
For example, grass or plants may be eaten by grasshoppers, rabbits, cattle and deer. These herbivores, in turn, may be eaten by carnivores such as frogs, birds, snakes, tigers or hawks, depending on their food habits.

BIODIVERSITY IN A FOREST

A forest is home to several kinds of plants and animals, which live in close relation with each other.
Forest plants: sal, teak, semal, sheesham, neem, palash, fig, khair, amla, bamboo, etc.
Forest animals: bear, jackal, porcupine, elephant, monkey, lion, tiger, leopard, butterfly, spider, etc.

USES OF FOREST

Forests are beneficial to people in several ways.
Provide timber: timber is used for making furniture, railway sleepers, carts, boats, ships, sports goods, ploughs, etc.
Provide food: tribal people living in forests take tubers, roots, leaves and fruits of plants as food.
Provide medicines: leaves of eucalyptus, neem and tulsi are well known for their medicinal value. Cinchona, ephedra, isabgol and aloe vera also have medicinal value.
Provide other forest products: gum, oil, spices, fodder, resins, bamboo, lac, silk, honey, etc.
Prevent soil erosion and floods: roots of trees bind soil particles together and prevent the soil from being washed or blown away.
Regulate the climate of a place: forests increase water vapour in the atmosphere through transpiration. This keeps the air cool and helps induce rain.
Improve the quality of soil: dead fallen leaves decay and form humus, which increases the porosity and fertility of the soil.
Reduce air pollution: forests reduce pollution by using carbon dioxide for photosynthesis and by collecting suspended particulate matter on their leaves. Trees thus help check global warming.
Control water flow: the thick layer of humus absorbs and holds rainwater like a sponge. The leaves of trees reduce the force of raindrops, allowing a gradual run-off of water. This prevents flash floods and ensures a perennial supply of water to streams, springs and wells.
Provide fuelwood: wood is one of the most important fuels for cooking in many rural areas. Charcoal is also used in winter to keep warm.
Aesthetic value: forests give a beautiful and pleasing look. Many people visit forests for recreation, because the temperature there is lower than normal and the air is pure. Forests are good places for picnics, hunting, hiking, camping, fishing and photography.

CONSERVATION OF FOREST

The maintenance and upkeep of forests is called forest conservation. The following steps should be undertaken:
1. Massive afforestation work should be undertaken to cover large areas of land with useful plants.
2. Large-scale cutting of forest trees must be stopped. If a few trees must be cut, more trees should be planted in their place.
3. Forest fires should be prevented. Huge forest areas are destroyed by fire every year, so people should avoid smoking or cooking in forest areas.
4. Overgrazing by cattle, horses, sheep and goats should be prevented.
5. Forests must be protected from insects and pests.
6. All activities leading to soil erosion should be controlled.
7. Air, water and soil pollution should be reduced so that trees and other vegetation can survive and develop.
8. Plants should be given free of cost to people for growing near their houses.
9. People should be made aware of the impact of forests on their lives through advertisements, television, radio and plays.
10. Guidelines of international organisations such as WWF and UNESCO for forest conservation should be followed.
11. Van Mahotsava, celebrated every year, should be made more popular, meaningful and effective.

3.Dependence of plant on animals   

◊ USE OF FOREST

Forest are beneficial to a man in several ways which are given below.

Forest increases the water vapour in the atmosphere by transpiratoion. Helps in keeping the air cool and also helps in inducing rain.