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Earthworms and frogs breathe through their skin because of which the skin of both the organisms is (a) moist and rough. (b) dry and rough. (c) dry and slimy. (d) moist and slimy.

(d) moist and slimy. Earthworm and frogs both breathe through their skin because of which their surface becomes moist and slimy. The main... View Article

Fish breathe with the help of gills which are richly supplied with blood vessels. The gills help the fish to (a) take in oxygen from the air. (b) take in oxygen dissolved in water. (c) absorb nutrients present in water. (d) release waste substances in water.

(b) take in oxygen dissolved in water. Fishes use gills for the exchange of gases. As the water enters through the mouth it flows through... View Article

Breathing is a process that (i) provides O2 to the body. (ii) breaks down food to release energy. (iii) helps the body to get rid of CO2. (iv) produces water in the cells. Which of the following gives the correct combination of functions of breathing? (a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iii) (d) (ii) and (iv)

c) (i) and (iii) Breathing is the process of inhaling oxygen into the body and exhaling carbon dioxide out of the body. It provides O2 to the... View Article

Yeast is used in the wine and beer industries because it respires (a) aerobically producing oxygen. (b) aerobically producing alcohol. (c) anaerobically producing alcohol. (d) anaerobically producing CO2.

(c) anaerobically producing alcohol. Yeast respires anaerobically to produce ethanol and CO2. Due to this property, it is used in the... View Article

Sometimes when we do heavy exercise, anaerobic respiration takes place in our muscle cells. What is produced during this process? (a) alcohol and lactic acid (b) alcohol and CO2 (c) lactic acid and CO2 (d) lactic acid only

d)Lactic acid only Explanation While doing heavy exercise such as running, cycling, weightlifting, etc., we need high energy which creates an... View Article

In towns and cities, generally, the bore wells have to be dug very deep to get water as compared to bore wells dug in villages. Give suitable reasons.

The reason is that the excessive use of water which depletes the groundwater. Towns and cities have asphalted roads and vast areas of soil are... View Article

Gardeners gently dig up the soil around the roots of garden herbs (plants) frequently. Give reasons.

Gardeners gently dig up the soil around the roots of garden herbs (plants) frequently because: It helps the plant roots to penetrate deep into... View Article

Why is soil erosion relatively less in dense forests as compared to barren, open fields?

In dense forests, the tree cover (canopy) prevents rain water from directly falling on the’ ground/soil. Also roots of the vegetation bind... View Article

Continuously water-logged soils are disadvantageous for plant growth. Why?

The main functions of roots are water absorption and uptake of oxygen from the pore space of the soil. But in waterlogged soils, water takes the... View Article

Rajasthan is a desert state in India. Once while travelling to Rajasthan by train, Boojho observed several streams and rivulets of rainwater during the journey but to his surprise, he did not see streams of water in the desert region even during rains. Help Boojho find a suitable explanation for this.

A large area of desert is covered by rocks and sand. When rain water falls on the land, it percolates immediately downwards in the gaps between... View Article

A man digging a pit found that he could dig with ease initially but digging became difficult as he went deeper. He could not dig beyond a depth of 5 feet. Provide a suitable scientific explanation.

It is easier to dig soil initially because the upper layer of the soil consists of topsoil and subsoil. These two horizons are composed of loose... View Article

Is it a good practice to remove grass and small plants that are growing in an open, unused field? Give a reason to support your answer.

No, because the soil surface is covered by plants. Their roots connect the soil particles and hold them in place. It prevents soil erosion,... View Article

How can a farmer convert acidic soil to neutral soil?

It is possible to convert acidic soil into neutral soil by adding lime to the soil. Lime is alkaline and neutralizes the acidity of the soil... View Article

Which of the following situations – ‘A’ or ‘B’ – is advantageous for the absorption of water and minerals? Why? Situation ‘A’: Growth and branching of roots in the C-horizon. Situation ‘B’: Growth and branching of roots in A and B horizons.

Situation ‘B’ is advantageous to plants because A and B-horizons are rich in water, minerals and humus. This layer is rich in... View Article

Read the following statements and give the appropriate terms for each of them. (a) The process of breakdown of rocks by the action of wind, water, sunlight. (b) Removal of topsoil during heavy rains or strong winds. (c) Accumulation of wastes in the soil generated by human activity which alter the features of the soil. (d) The process of movement of water into deeper layers of soil.

(a) Weathering The scenes of the world are continuously mutating. Sun, rain, frost, and wind are breaking down even the most solid of the rocks... View Article

The components of loamy soil are , and __.

sand, clay and slit Loamy soil is a mixture of sand, clay and silt. Besides these particles, the loamy soil contains humus in it. This... View Article

The soil has particles of different sizes. Arrange the words given below in increasing order of their particle size. (Rock, Clay, Sand, Gravel, Silt)

The words according to increasing order of their particle size are, Clay < Slit < Sand < Gravel < Rock Soil is usually referred to... View Article

Read the following statements with reference to the soil. i) Weathering is a very fast process of soil formation. ii) Percolation of water is faster in sandy soils. iii) Loamy soil contains only sand and clay. iv) Topsoil contains the maximum amount of humus. Choose the correct statements from the above. (a) (ii) and (iv) (b) (i) and (iii) (c) (ii) and (iii) (d) (i) and (ii)

a) (ii) and (iv) Statements (ii) and (iv) are correct. Options (i) and (iii) are wrong. (i) Weathering is a slow process of soil formation... View Article

Soil conservation measures are mainly aimed at protecting which of the following? (a) Plants (b) Topsoil (c) Subsoil (d) Soil organisms

b) Top soil Topsoil is nutrients making and also rich in humus. It is fertile to grow plants. The topsoil is the topmost layer of the soil. It... View Article

Availability of water and minerals in the soil for maximum absorption by roots is in the – (a) B-horizon (b) C-horizon (c) A-horizon (d) surface of soil

c) A-horizon A-horizon is also known as topsoil. This layer is basically porous, soft, and also can retain water. It contains the maximum... View Article

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