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NCERT Solutions for Class 8 Science Chapter 7 : Conservation Of Plants And Animals

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Chapter 7 : Conservation Of Plants And Animals

We saw in Class VII that Paheli and Boojho had visited the forest along with Prof. Ahmad and Tibu. They were eager to share their experiences with their classmates. Other children in the class were also eager to share their experiences as some of them had visited Bharatpur Sanctuary. Some others had heard about Kaziranga National Park, Lockchao Wildlife Sanctuary, Great Nicobar Biosphere Reserve and Tiger Reserve, etc.

7.1 Deforestation And Its Causes

A great variety of plants and animals exists on earth. They are essential for the wellbeing and survival of mankind. Today, a major threat to survival of these organisms is deforestation. We know that deforestation means clearing of forests and using that land for other purposes. Trees in the forest are cut for some of the purposes mentioned below:

 1. Procuring land for cultivation.
 2. Building houses and factories.

7.2 Consequences Of Deforestation

Paheli and Boojho recalled the consequences of deforestation. They remembered that deforestation increases the temperature and pollution level on the earth. It increases the level of carbon dioxide in the atmosphere. Ground water level also gets lowered. They know that deforestation disturbs the balance in nature. They were told by Prof. Ahmad that if cutting of trees continues, rainfall and the fertility of the soil will decrease.

7.3 Conservation Of Forest And Wildlife

Having become aware of the effects of deforestation, Paheli and Boojho are worried. They go to Prof. Ahmad and ask him how forests and wildlife can be saved.

Prof. Ahmad organises a visit to a biosphere reserve for Paheli, Boojho and their classmates. He selects a place named Pachmarhi Biosphere Reserve. He knows that the plants and animals found here are similar to those of the upper Himalayan peaks and to those belonging to the lower western ghats. Prof. Ahmad believes that the biodiversity found here is unique. He requests Madhavji, a forest employee, to guide the children inside the biosphere reserve. He explains that preserving areas of such biological importance make them a part of our national heritage.

7.4 Biosphere Reserve

Children along with Prof. Ahmad and Madhavji enter the biosphere reserve area. Madhavji explains that biosphere reserves are the areas meant for conservation of biodiversity. As you are aware that biodiversity is the variety of plants, animals and microorganisms generally found in an area. The biosphere reserves help to maintain the biodiversity and culture of that area. A biosphere reserve may also contain other protected areas in it. The Pachmarhi Biosphere Reserve consists of one national park named Satpura and two wildlife sanctuaries named Bori and Pachmarhi (Fig. 7.1).

7.5 Flora And Fauna

As the children walk around the biosphere reserve they appreciate the green wealth of the forest. They are very happy to see tall teak trees and animals inside the forest. Suddenly, Paheli finds a rabbit and wants to catch it. She starts running after it. Prof. Ahmad stops her. He explains that animals are comfortable and happy in their own habitat. We should not disturb them. Madhavji explains that some animals and plants typically belong to a particular area. The plants and animals found in a particular area are termed flora and fauna of that area.

7.6 Endemic Species

Soon the group quietly enters the deep forest. Children are surprised to see a very big squirrel. This squirrel has a big fluffy tail. They are very curious to know about it. Madhavji tells them that this is known as the giant squirrel and is endemic to this area.

7.7 Wildlife Sanctuary

Soon Paheli sees a board with ‘Pachmarhi Wildlife Sanctuary’ written on it.

Prof. Ahmad explains that, like reserve forests, wildlife sanctuaries provide protection and suitable living conditions to wild animals. Madhavji further explains that sanctuaries are places where killing (poaching) or capturing of animals is strictly prohibited.

7.8 National Park

On the roadside there was another board on which was written ‘Satpura National Park’.

Children are now eager to go there. Madhavji tells them that these reserves are large and diverse enough to protect whole sets of ecosystems. They preserve flora, fauna, landscape and historic objects of an area. Satpura National Park is the first Reserve Forest of India. The finest Indian teak is found in this forest.

7.9 Red Data Book

Prof. Ahmad explains about Red Data Book to the children. He tells them that Red Data Book is the source book which keeps a record of all the endangered animals and plants. There are different Red Data Books for plants, animals and other species. (For further details about Red Data Book.

7.10 Migration

The excursion party then enters deeper into the forest under the guidance of Madhavji. They sit near the Tawa Reservoir to relax for some time. Paheli observes some of the birds near the river. Madhavji tells the children that these are the migratory birds. These birds have flown here from other parts of the world.

7.11 Recycling Of Paper

Prof. Ahmad draws the attention of the children to another cause of deforestation. He tells them that it takes 17 full grown trees to make one tonne of paper. Therefore, we should save paper. Prof. Ahmad also tells that paper can be recycled five to seven times for use. If each student saves at least one sheet of paper in a day, we can save many trees in a year. We should save, reuse used paper and recycle it. By this we not only save trees but also save energy and water needed for manufacturing paper. Moreover, the amount of harmful chemicals used in paper making will also be reduced.

7.12 Reforestation

Prof. Ahmad suggests that the answer to deforestation is reforestation. Reforestation is restocking of the destroyed forests by planting new trees. The planted trees should generally be of the same species which were found in that forest. We should plant at least as many trees as we cut. Reforestation can take place naturally also. If the deforested area is left undisturbed, it reestablishes itself. In natural reforestation there is no role of human beings. We have already made a tremendous damage to our forests. If we have to retain our green wealth for generations, plantation of more trees is the only option.



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NCERT Solutions for Class 8 Science Chapter 8 : Cell – Structure And Functions

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Chapter 8 : Cell – Structure And Functions

You have already learnt that things around us are either living or non-living. Further, you may recall that all living organisms carry out certain basic functions. Can you list these functions?

Different sets of organs perform the various functions you have listed. In this chapter, you shall learn about the basic structural unit of an organ, which is the cell. Cells may be compared to bricks. Bricks are assembled to make a building. Similarly, cells are assembled to make the body of every organism.

8.1 Discovery Of The Cell

Robert Hooke in 1665 observed slices of cork under a simple magnifying device. Cork is a part of the bark of a tree. He took thin slices of cork and observed them under a microscope. He noticed partitioned boxes or compartments in the cork slice (Fig. 8.1).

8.2 The Cell

Both, bricks in a building and cells in the living organisms, are basic structural units [Fig. 8.2(a), (b)]. The buildings, though built of similar bricks, have different designs, shapes and sizes. Similarly, in the living world, organisms differ from one another but all are made up of cells. Cells in the living organisms are complex living structures unlike non-living bricks.

8.3 Organisms Show Variety In Cell Number, Shape And Size

How do scientists observe and study the living cells? They use microscopes which magnify objects. Stains (dyes) are used to colour parts of the cell to study the detailed structure.

There are millions of living organisms. They are of different shapes and sizes. Their organs also vary in shape, size and number of cells. Let us study about some of them.

8.4 Cell Structure And Function

You have learnt that each living organism has many organs. You have studied in Class VII about the digestive organs which together constitute the digestive system. Each organ in the system performs different functions such as digestion, assimilation and absorption. Similarly, different organs of a plant perform specific/specialised functions. For example, roots help in the absorption of water and minerals. Leaves, as you have learnt in Class VII, are responsible for synthesis of food.

8.5 Parts Of The Cell

Cell Membrane
The basic components of a cell are cell membrane, cytoplasm and nucleus (Fig. 8.7). The cytoplasm and nucleus are enclosed within the cell membrane, also called the plasma membrane. The membrane separates cells from one another and also the cell from the surrounding medium. The plasma membrane is porous and allows the movement of substances or materials both inward and outward.

8.6 Comparison Of Plant And Animal Cells

If you recall Activities 8.3 and 8.4, you should be able to compare plant and animal cells. Observe the plant and animal cell carefully in Fig. 8.7 (a), (b).

Let us tabulate the similarities and disinguishing features of plant and animal cells. Only a few features are mentioned. You may add more in Table 8.1.