Notes On Introduction to Forest - CBSE Class 7 Science
Forests - An ecosystem Forests include varieties of living organisms in them.  Forests are constantly changing ecosystem. The organisms living in the forests are interdependent on each other. Forests either directly or indirectly affect the human beings also. Structure of the forests Plants in the forests are divided into three categories namely, herbs, shrubs and trees. All these categories vary in their size, shape and other characteristics. These are also covered by creepers and climbers. Crown: The part of the tree with branches resting on the trunk is called as crown of the tree. Crowns of different trees exist in different sizes making up storeys in the forest. The horizontal layers formed by crowns of different trees are termed as under storeys. Giant and topmost storey is formed by tall trees. Shrubs and tall grasses make up the middle storey. Lower storey is made up of herbs. Canopy: The roof like structure formed by branches of tall trees is termed to be canopy. Canopy prevents direct downpour of rainfall. This in turn prevents water stagnation in the forests. Soil: The soil of the forest is moist and warm as it is covered with leaves and fruits. Soil in the forest is very fertile and the top most layer of organic matter is called as humus. The floor of the forest is soft and spongy due to dead and decaying matter.  Saprophytic organisms and micro-organisms convert the dead waste into black organic substance called as humus. Forests - Interdependence There is lot of interdependence between organisms in the forests. Organisms living in the forest depend upon abiotic factors like air, availability of water, temperature, sunlight etc. Wild life in the forest include both plants and animals. All these organisms are interdependent on one and other.  Plants can synthesise their own food and store in their body.  Animals make use of this food for survival. Some animals depend on smaller animals for food.  In turn, plants also depend on animals for the processes like pollination and seed dispersal.  Different agents of seed dispersal include animals like monkeys, buffaloes, birds etc.  Animals also add their excreta to the soil which is decomposed to add nutrients to it.  Dead bodies of animals also decay and release nutrients to the soil. These nutrients are utilised by the plants for their growth. Food chain Chain of events occurring in the environment to transfer energy from one level to another is referred to as food chain. Food chains help in studying the interdependence of animals and plants. Each level in the food chain is called as trophic level. Energy is transferred form one trophic level to another level in a food chain. Food chains maintain a balance in the environment by cycling the nutrients absorbed by plants from the soil.  Based on the nutrition of an organism, food chain comprises of different levels which include producers, consumers and decomposers. a) Source of energy: Sun is the ultimate source of energy for all living organisms on earth. b) Producers: Plants are called producers as they prepare their own food by the process of photosynthesis. Photosynthesis involves the conversion of solar energy into chemical energy to synthesise starch. Energy from the sun enters the food chain. Photosynthesis is a process by which green plants can synthesise glucose from raw materials like carbon dioxide and water in the presence of sunlight and chlorophyll. First level in the food chain is occupied by plants. c) Consumers: Based on the food they eat, consumers are categorised into primary consumers, secondary consumers and tertiary consumers. Primary consumers are the animals which directly consume plants. Hence, herbivorous animals occupy the second trophic level in the food chain. Energy from plants is transferred to herbivores. Secondary consumers are the animals which consume herbivores and are called as carnivorous animals. They occupy the third trophic level in the food chain. Energy from herbivores is transferred to carnivores. Tertiary consumers are the carnivores which consume other carnivorous animals. They occupy the top most level in the food chain. Energy from the third level of the food chain is transferred to the final level. d) Decomposers: These organisms occupy different level in the food chain. These play an important role in the food chain as they remove dead and decaying matter from the environment. Decomposers are an important part of the ecosystem. Food web Number of food chains connected to form a network is called a food web. Food web explains the relationship of different organisms in different ways. Conservation of forests Forests proved to be our lifeline should be conserved. Different practices and steps are to be taken to conserve forests. Forests should be protected from over exploitation of the resources provided by them. This requires planned collection of the products they provide us.  Forest fires should be controlled. Necessary steps must be taken during lightnings and storms to control forest fires.  Afforestation should be practiced in order to convert barren lands into forests. Forests should be protected from the diseases caused by various pathogens. Forests should be protected from the action of deforestation and overgrazing. Forests – A case study There are many forests in India. One of the Indian state with great forest resource is Kerala. Kerala Kerala, one of the India's southern states is also known as "God's own country". It is rich in natural vegetation.  The forests are spread over a large area. They are tropical wet, evergreen, partly evergreen, deciduous and dry forests.  Some plants found in these forests are known for their medicinal value.  These forests have given Kerala its healing touch in the form of Ayurvedic medicines for treating various ailments.  Kerala's forests have huge neem trees that can grow up to a height of 50 to 65 feet. The neem tree has high medicinal value and is said to treat around 40 diseases. The wood of the neem tree is used to make a musical instrument called the dhol.  Trees such as the bamboo, which can grow at the rate of 45 inches in a day, the fig tree, the amla tree or the Indian gooseberry, the sal tree, the sandal wood tree, the teak tree and many more are found in these forests. An example of forest is Wayanad Wildlife Forest. Wayanad Wildlife Forest It is a large collection of flora and fauna. Endemic species are the animals and plants found in a specific area. Many endemic species of animals, such as pale-faced monkeys called bonnet macaques, striped-neck mongoose, small Indian civet, striped hyena, jackal, Indian fox, wild bear, giant squirrel, bison, chital and others, are found in this forest.

#### Summary

Forests - An ecosystem Forests include varieties of living organisms in them.  Forests are constantly changing ecosystem. The organisms living in the forests are interdependent on each other. Forests either directly or indirectly affect the human beings also. Structure of the forests Plants in the forests are divided into three categories namely, herbs, shrubs and trees. All these categories vary in their size, shape and other characteristics. These are also covered by creepers and climbers. Crown: The part of the tree with branches resting on the trunk is called as crown of the tree. Crowns of different trees exist in different sizes making up storeys in the forest. The horizontal layers formed by crowns of different trees are termed as under storeys. Giant and topmost storey is formed by tall trees. Shrubs and tall grasses make up the middle storey. Lower storey is made up of herbs. Canopy: The roof like structure formed by branches of tall trees is termed to be canopy. Canopy prevents direct downpour of rainfall. This in turn prevents water stagnation in the forests. Soil: The soil of the forest is moist and warm as it is covered with leaves and fruits. Soil in the forest is very fertile and the top most layer of organic matter is called as humus. The floor of the forest is soft and spongy due to dead and decaying matter.  Saprophytic organisms and micro-organisms convert the dead waste into black organic substance called as humus. Forests - Interdependence There is lot of interdependence between organisms in the forests. Organisms living in the forest depend upon abiotic factors like air, availability of water, temperature, sunlight etc. Wild life in the forest include both plants and animals. All these organisms are interdependent on one and other.  Plants can synthesise their own food and store in their body.  Animals make use of this food for survival. Some animals depend on smaller animals for food.  In turn, plants also depend on animals for the processes like pollination and seed dispersal.  Different agents of seed dispersal include animals like monkeys, buffaloes, birds etc.  Animals also add their excreta to the soil which is decomposed to add nutrients to it.  Dead bodies of animals also decay and release nutrients to the soil. These nutrients are utilised by the plants for their growth. Food chain Chain of events occurring in the environment to transfer energy from one level to another is referred to as food chain. Food chains help in studying the interdependence of animals and plants. Each level in the food chain is called as trophic level. Energy is transferred form one trophic level to another level in a food chain. Food chains maintain a balance in the environment by cycling the nutrients absorbed by plants from the soil.  Based on the nutrition of an organism, food chain comprises of different levels which include producers, consumers and decomposers. a) Source of energy: Sun is the ultimate source of energy for all living organisms on earth. b) Producers: Plants are called producers as they prepare their own food by the process of photosynthesis. Photosynthesis involves the conversion of solar energy into chemical energy to synthesise starch. Energy from the sun enters the food chain. Photosynthesis is a process by which green plants can synthesise glucose from raw materials like carbon dioxide and water in the presence of sunlight and chlorophyll. First level in the food chain is occupied by plants. c) Consumers: Based on the food they eat, consumers are categorised into primary consumers, secondary consumers and tertiary consumers. Primary consumers are the animals which directly consume plants. Hence, herbivorous animals occupy the second trophic level in the food chain. Energy from plants is transferred to herbivores. Secondary consumers are the animals which consume herbivores and are called as carnivorous animals. They occupy the third trophic level in the food chain. Energy from herbivores is transferred to carnivores. Tertiary consumers are the carnivores which consume other carnivorous animals. They occupy the top most level in the food chain. Energy from the third level of the food chain is transferred to the final level. d) Decomposers: These organisms occupy different level in the food chain. These play an important role in the food chain as they remove dead and decaying matter from the environment. Decomposers are an important part of the ecosystem. Food web Number of food chains connected to form a network is called a food web. Food web explains the relationship of different organisms in different ways. Conservation of forests Forests proved to be our lifeline should be conserved. Different practices and steps are to be taken to conserve forests. Forests should be protected from over exploitation of the resources provided by them. This requires planned collection of the products they provide us.  Forest fires should be controlled. Necessary steps must be taken during lightnings and storms to control forest fires.  Afforestation should be practiced in order to convert barren lands into forests. Forests should be protected from the diseases caused by various pathogens. Forests should be protected from the action of deforestation and overgrazing. Forests – A case study There are many forests in India. One of the Indian state with great forest resource is Kerala. Kerala Kerala, one of the India's southern states is also known as "God's own country". It is rich in natural vegetation.  The forests are spread over a large area. They are tropical wet, evergreen, partly evergreen, deciduous and dry forests.  Some plants found in these forests are known for their medicinal value.  These forests have given Kerala its healing touch in the form of Ayurvedic medicines for treating various ailments.  Kerala's forests have huge neem trees that can grow up to a height of 50 to 65 feet. The neem tree has high medicinal value and is said to treat around 40 diseases. The wood of the neem tree is used to make a musical instrument called the dhol.  Trees such as the bamboo, which can grow at the rate of 45 inches in a day, the fig tree, the amla tree or the Indian gooseberry, the sal tree, the sandal wood tree, the teak tree and many more are found in these forests. An example of forest is Wayanad Wildlife Forest. Wayanad Wildlife Forest It is a large collection of flora and fauna. Endemic species are the animals and plants found in a specific area. Many endemic species of animals, such as pale-faced monkeys called bonnet macaques, striped-neck mongoose, small Indian civet, striped hyena, jackal, Indian fox, wild bear, giant squirrel, bison, chital and others, are found in this forest.

#### Activities

 Activity 1 Si.edu has sparked an interactive audiovisual session to explain different organisms of the forest. It brings in information about different layers of the forest forming the canopy. It emphasises on the different associations between plants and animals. It also shows different wildlife living in the forest ecosystem. Different organisms occupying different trophic levels of the food chains in the forest are discussed. They include producers,consumers and decomposers.   Go to Activity Activity 1 Sheppardsoftware.com has compiled a wonderful game to show the organisms living in the forest which occupy the different levels in the food chain. Student has to just follow the instructions to play the game. Student has to categorise the dispalyed organism as producer or consumer or a decomposer.This makes the student well versed in clasiifying the organisms based on their food habits. Go to Activity

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