3rd Class Science Our Environment Environment

   Environment

Every things in our surrounding, whether living or non living constitute environment. Environment includes everything, that is, vegetation, water, microorganisms, soil, rocks, and atmosphere.

         Components of Environment

All the things that exist in the environment has been classified into two groups on the basis of living and non living. Living things are called Biotic components and non-living things are called Abiotic components. Plants, animals, humans, microorganisms etc. are biotic components whereas water, air, soil, rock etc. are abiotic components.

         Soil

Soil is a natural resource made up of tiny particles of broken rock, mineral, clay and humus etc. Plants are grown in the top layer of the soil. Soil contains nutrients, water, minerals, humus, and air, which are essential for the growth of the plants. Many living organism like ants, beetles, earth worm, worms, snails etc. make their homes in the soil. Earthworm increases the fertility of the soil by making it porus. Survival on the earth is not possible without soil.

       Formation of Soil

Soil is formed by the process of weathering of rocks. Breaking of rocks into smaller particles takes place because of wind, rain and the heat of the sun. Dead plant and animals got mixed up with those broken pieces and results in the formation of soil. It takes thousands of years to break rocks into fine particles. Different types of soils are found in different places of India.  

       Layers of Soil

The earth is made up of three layers of soil:

Top Soil

Sub Soil

Bed Rock

       Top Soil

This uppermost layer is rich in minerals and humus. Humus makes the soil fertile. This layer is soft and can retain water. Hence most plants are grown in this layer.

It also provides habitat to many organisms like earth worm, rat, snakes, beetles etc. This layer is dark in colour.

         Sub Soil

It lies below top soil, and is comparatively harder and contains less amount of humus and other nutrients. It is red or grey in colour.

         Bed Rock

It lies below subsoil and is soft porus on the upper side and hard non porus in the inner side. It can't be dig manually.

Look at the following picture of the layers of rock:

           Types of Soil

Mainly three types of soil are found:

Sandy Soil

Clayey Soil

Loamy Soil

         Sandy Soil

It is made up of small fine grains particles that makes it porus. It has very less water holding capacity. Because particles of sandy soil are loosely packed and can allow water to easily pass through it. Soil transported by wind generally consists of sandy soil.

       Clayey Soil

This soil consists of very fine particles which are stick together. Since particles in clayey soil are closely packed, they provide little aeration. Its water holding capacity is very good. Clayey soil is very good for the growth of plants. This soil is also used in making toys, pots and other articles.

         Loamy Soil

It contains a mixture of sand, clayey and humus altogether. Its water holding capacity and air carrying capacity is satisfactory for the growth of plants, as compare to the sandy and clayey soil. Maximum amount of humus is present in this soil. The size of particles in loamy soil is less than that of sandy soil and greater than that of clayey soil.

         Soil Degradation

Insensible activities of human have deteriorated one of the major life supporting resource of this earth.

Cutting down of trees every day in order to satisfy the needs of large population has resulted in soil erosion.

Soil erosion is the process of removal of top layer of the soil, by wind or running water. Overgrazing and use of chemicals as fertilizers has also spoiled our soil and made it unfit for the growth of plants.

Growing same crops year after year on the same piece of land has resulted in the loss of nutrients from the soil.

Crops should be grown in rotation. If cereal crops like wheat, rice, jowar, bajra are grown in one year the next year leguminous plants like pulses should be grow to restore the essential nutrients in the soil. Legumes add nutrients to the soil naturally. The above process is called crop rotation and a good practice to prevent infertility.

       Conservation of Soil

Soil can be conserved by stopping ruthless cutting down of trees and motivating people towards afforestation. It will also stop soil erosion. Overgrazing should also be avoided for the conservation of soil.

Manures and fertilizers - Due to repeated growing of crops in the same field reduces or absorbs certain essential nutrients of the soil, making it infertile. Fertility of the soil can be maintained with the help of manures and fertilizers. Manures like gobar khad and fertilizers like urea, phosphates and nitrates are added to the soil to restore its nutritive value.

Construction of dams against the rivers controls the damage of soil by flood and fast flowing water.

    Coconut is grown in which one of the following types of soil?

(a) Clayey soil

(b) Loamy soil

(c) Sandy soil

(d) All of these

(e) None of these

Answer: (c)

Explanation

Coconuts are mostly found on sea beeches and sea beaches are rich in sandy soil. Therefore, option (c) is correct and rest of the options is incorrect.

     Which one of the following supplies minerals to the plants?

(a) Humus

(b) Fertilizers

(c) Manures

(d) Rhizobium bacteria

(e) All of these

Answer: (e)

Explanation

Humus is dead decayed organic matter that supplies minerals to the soil. Fertilizers and manures also add up nutrients to the soil. Rhizobium bacteria lives in the roots of pulses plants and fix atmospheric nitrogen into usable form for the plants. Therefore, option (e) is correct and rest of the options is incorrect.