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Whenever we feel drowsy or sleepy, we start yawning. Does yawning help us in any way?

When we feel drowsy, rate of breathing is decelerated, that means enough oxygen is not supplied to lungs, it makes us yawn. And when we yawn, we... View Article

On a very cold morning, Boojho and Paheli were talking with each other as they walked down to their school. They observed that the air coming out of their mouth looked like smoke. They were amused and wondered how it happened. Help them find the answer.

On a cold day, the warm and moist air exhaled by us condenses into mist when it comes in contact with the cold air of the atmosphere. This looks... View Article

On average, an adult human being at rest breathes 15–18 times per minute. The breathing rate, however, may differ under different conditions. Arrange the following activities given in the box in order of increasing breathing rates and give a reason for your answer. (sleeping, cycling, brisk walk, watching T.V.)

Sleeping > Watching > T.V. > Brisk Walk > Cycling The breathing rate becomes faster when we are working. The more is strenuous work,... View Article

Which gas present in the air is essential for aerobic respiration? What is the role of oxygen during respiration?

Aerobic respiration occurs in the presence of oxygen gas or O2. Oxygen oxidizes the food and breaks it into smaller molecules so that energy... View Article

Pick the odd-one-out from each of the groups given below on the basis of respiratory organs. Give a reason for your answer. (a) cockroach, grasshopper, snail, ant (b) lizard, cow, earthworm, snake (c) crocodile, whale, dolphin, fish (d) snake, tadpole, crow, goat

Answer: The respiratory system is an organ system responsible for exchanging gases in animals. It is the system that uses oxygen and expels... View Article

Fill in the blanks with suitable words. (a) The roots of a plant take up oxygen from the trapped between the particles. (b) Diaphragm forms the _ of the chest cavity. (c) Exchange of gases in the leaves takes place with the help of . (d) Cockroaches breathe with the help of air tubes called _____.

a) The roots of a plant take up oxygen from the air trapped between the soil particles. The roots use up the oxygen available to them from the... View Article

Mark the following statements as True or False. Exhaled air has more percentage of CO2 than inhaled air.

True The percentage of CO2 in inhaled air is 0.04% whereas in exhaled air it is 4.4%. Therefore, we can say that exhaled air has more... View Article

Mark the following statements as True or False. Insects have spiracles on the lower surface of the body.

False Insects have spiracles on the sides of the body. Spiracles are openings or tiny pores on the surface of some animals, which usually lead... View Article

Mark the following statements as True or False. (a) Oxygen breaks down glucose outside the cells of organisms.

False Oxygen breaks down glucose inside the cells of organisms.. At first, glucose-containing 6 carbon molecules are broken in the cytoplasm of... View Article

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

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