These DAV Class 7 Science Notes and DAV Class 7 Science Chapter 15 Notes – Forests act as excellent revision resources, particularly in preparation for board exams.
Forests Class 7 DAV Notes
→ Forest: An area with a high density of trees is called forest.
→ Components of a forest:
- Biotic Component: The living beings in the forest make biotic components. Plants, animals, fungi, bacteria, etc. are the biotic components.
- Abiotic Component: The non-living things make the abiotic components of a forest. Soil, air and water are abiotic components.
→ Food Chain: Green plants prepare food through the process of photosynthesis. This food is utilised by other living beings. The consumption of food by various organisms happens in the form of a chain. This is called food chain. An example of a simple food chain is given below:
Grass → Deer → Lion
In this case, grass is the producer, deer is the primary consumer and lion is the secondary consumer. This can be shown as follows:
Producer → Primary consumer → Secondary consumer
→ Food Web: Many food chains are interlinked in a forest environment. This makes the food web. So, food web is a web which is made by interlinking of various food chains.
→ Decomposers: Bacteria, fungi and some worms feed on dead and decaying materials. While doing so, they decompose the dead and decaying materials and return the raw materials back to the environment. Due to this, these organisms are called decomposers.
→ The Layers of Forest:
→ Forest Floor Layer: This layer comprises decomposing leaves, animal droppings, dead trees and animals. All of them decay and form humus in the soil. This enhances the soil fertility.
→ Understory Layer: This layer is made of bushes, shrubs and young trees. These plants are adapted to live in the shade of the canopy.
→ Canopy: The mass of intertwined branches of a tree makes the canopy. This is also called the crown of a tree. This part of the tree receives the maximum sunlight and that is why this is the part where maximum food is produced.
→ Emergent Layer: This layer exists in tropical rainforest. It is composed of a few scattered trees which tower over the canopy.
→ Crown of Trees: The branches, twigs and leaves at the top of the trunk of a tree make the crown. The shape of the crown is affected by the climate in which a tree grows.
→ The crown of the trees near equator is almost flat at top. This is due to the maximum amount of sunlight falling near the equator. The flat crown gets maximum sunlight and hence is able to produce the maximum food.
→ The crown of trees in Arctic Circle is cone-shaped. The sunlight reaches obliquely in these areas. Conical shape is more suited to exploit sunlight in these conditions.
→ Importance of Forests:
- Forests are the habitat for a variety of living beings.
- Agriculture and animal husbandry are dependent on forests.
- Forests help in improving the moisture in the atmosphere and thus help in bringing precipitation.
- Forests clean the air by maintaining the balance of oxygen and carbon dioxide in the atmosphere.
- Forests produce lot of humus and thus help in maintaining soil fertility.
- Forests help in recharge of groundwater.
- Forests prevent soil erosion.
- Forests are source of a variety of resources; like medicinal herbs, forest produce and raw materials for industrial products.
→ Deforestation: Indiscriminate cutting or over harvesting of trees for timber or pulp, or to clear the land for various human activities is called deforestation.
→ Consequences of Deforestation:
- Clearing of forests disturbs the carbon cycle. This leads to excess of carbon dioxide in the atmosphere.
- Clearing of forests hampers the natural recharge of groundwater. This leads to shortage of drinking water.
- Clearing of forests leads to soil erosion and ultimately to desertification.
- Clearing of forests results in increased occurrences of floods and draughts.
- Many species lose their habitat and become extinct because of deforestation.
→ Some Common Trees in India:
→ Banyan: This is a huge tree. Its branches send of new shoots which form roots and go into the ground. Such roots provide additional support to the banyan tree.
→ Teak: This tree is used in making furniture and doors. Its bark has some medicinal values.
→ Neem: Neem is very popular because of its medicinal properties. Neem leaves and seeds are used in making many ayurvedic medicines.
→ Eucalyptus: Eucalyptus is a tall tree with whitish trunk. Eucalyptus oil is used in making various medicines. The pulp of eucalyptus is used in making paper.
→ Deodar: This is also known as Himalayan Cedar. It is a large evergreen tree which reaches a height of 40-50 m. Its trunk can be upto 3 m in diameter. Its wood is used for making matchsticks.
→ Sal: It is a large deciduous tree. It is worshipped among the Buddhists and Hindus.
→ Amalatas: Because of its yellow flowers, it is also known as the Golden Shower Tree. It is an ornamental plant.
→ Ashoka: This tree is considered as sacred. It is used for its ornamental value.
→ Forest: An area with dense tree cover is called forest.
→ Biotic components: Living beings in an ecosystem.
→ Abiotic components: Non-living things in an ecosystem.
→ Producers: Green plants are called producers because they produce food.
→ Primary consumers: Herbivores are called primary consumers because they directly take food from plants.
→ Secondary consumers: Carnivores are called secondary or tertiary consumers because they indirectly take food from plants.
→ Food chain: A linear chain showing relationship among prey and predator.
→ Food web: A network of may food chains.
→ Deforestation: Indiscriminate cutting of trees to make way for human activities.
→ Crown: A combination of branches, twigs and leaves of trees.