Storis and knowledge

Deforestation  Excessive cutting of tree in a forest is called defforestation. It leads to soil erosion. When large stretches of forest land are cleared for growing crops, raising livestock of building industries, they are exposed to nature factor. Devoid of natural vegetation, the soil in These areas get eroded by wind and flowing water. Afforestation  Planting of more trees and a large scale in place of cut down tree is called affirmation. If the tree have to be cut down from the forests up for various need then new trees should be planted in the place of the cut down trees. Grasses should be grown on hill slopes to prevent soil erosion gases do not  need much area and spread very quickly. Grasses hold the soil in place and prevent it from getting eroded.

 Muscular System  we know that our body make movement by the help of movable joints. Bones cannot move by themselves. The bones are attached which muscles and flexible like rubber plates. Muscles work by contraction and relaxation. White strong fibres which attach muscles with the bone are known as tendons. There are about 650 different muscles in our body. Muscles work in pairs. When one muscles contract the other is relax. How does muscles work? Muscles produce Movement in the body by pulling on the bones. Therefore, to separate muscles are needed to move a joint. When muscles contracts,it becomes shorter and thicker. When a muscle relaxes,it becomes longer and thinner. For example,the movement of arms are controlled by to muscles ---biceps and triceps.If we want to pull up our arms, the bicep which are are joined to the armsin front contract, while the triceps which are at the back of the arms relax . If you want to low down our arms ,our biceps relax while the ...

Bones  when we touch our hands,feet,back etc.We feel soft skin and under skin, we find hard structures. These Structures are bones. Bones from the framework of our body these are hard and of white colour.Bones are mainly made of calcium and phosphorus.The bones are filled with a soft, fatty substance called the bone marrow.White blood cells (WBC )and red blood cell (RBC)are performed in the bone marrow. RBC are present in the hemoglobin of the body.WBC fight against the introduction and protect our body organ the disease. Bones have tiny pores to connect them with nerves and blood vessels.The bones in different part of the body are different.The framework of bones is called skeleton. Human skeleton and how does it work you will learn in next page