Class 7 Science Chapter 6 MCQ

Fish is the odd one, as most fish breathe through their gills and do not have lungs.

The process of releasing energy from food is called respiration. Respiration occurs in all the living cells. The process of respiration involves taking in oxygen into the cells, using it for releasing energy by burning food, and then eliminating the waste products carbon dioxide and water from the body.

It is not only the human beings who need energy but also all the other animals and plants also require energy.

Here, all these statements are correct. Hence, your answer will be option [D]

When we breathe in or inhale, then two things happen at the same time. First is, the muscles between the ribs contract causing the rib cage to move upward and outward and second is, the diaphragm contracts and moves downward. The upward and outward movement of the rib cage, as well as the downward movement of the diaphragm, both increases the space in the chest cavity and make it larger. When we breathe out or exhale, even then two things happen at the same time. First is, the muscles between the ribs relax causing the ribcage to move downward and inward and second is, the diaphragm relaxes and moves upward. The downward and inward movement of rib cage, as well as the upward movement of diaphragm, both decreases the space in our chest cavity and make it is smaller.

Exhaled air contains more carbon dioxide than inhaled air. The air which we inhale contains a lower proportion of carbon dioxide. And during respiration when oxygen breaks down glucose food, then some carbon dioxide is produced. So, the exhaled air that comes out after the process of respiration contains a higher proportion of carbon dioxide.

The number of times a person breathes in one minute is called breathing rate. The average breathing rate in an adult human being at rest is 15 to 18 times per minute. During running, the breathing rate of an adult human being can increase up to 25 per minute or even more.

The process of respiration is the reverse of photosynthesis. This is because photosynthesis is the making of food like glucose by absorbing sunlight energy whereas respiration is the breaking of food like glucose to release energy.

The breakdown of food like glucose to release energy can occur in the presence of oxygen as well as in the absence of oxygen. Based on these, there are two types of respiration as aerobic respiration and anaerobic respiration.

Earthworms and frogs have moist and slimy skin that helps them to absorb the oxygen for respiration.

When extra energy is needed, anaerobic respiration can take place in our muscles for a short time not a long time.

The amount of air available to the person is less than that available on the ground.

Fish has special organs called gills that help it to use oxygen dissolved in water. Gills are projections of the skin that are well supplied with blood vessels for exchange of gases.

The accumulation of lactic acid in the muscles causes muscle cramps. During running or heavy exercise, we get muscles cramps. Generally, muscle cramps mean a painful contraction of muscles are called cramps. During heavy exercise some of our muscles respire anaerobically. The anaerobic respiration by muscles bring about partial breakdown of glucose or food to form lactic acid. This lactic acid accumulates in the muscles and reason for pain.

Here, all these statements are correct. Hence, your answer will be option [D]

Breathing is a process by which air rich and oxygen is taken inside the body and air rich in carbon dioxide is expelled from the body, with the help of respiratory organs. It is a continuous process which goes on all the time and throughout the life of an organism.

The breathing rate of a person increases when he does gym or weightlifting. Remember, the breathing rate of a person is a slowest when he is sleeping because minimum energy is required by the body during sleep which can be provided by a slow rate of breathing. The breathing rate of a person increases with increased physical activity (like exercise, running, gym, weightlifting etc.). When the breathing rate increases, greater amount of air goes into the lungs. With more air going into the lungs, the blood can absorb oxygen at a faster rate. Thus, faster breathing supplies more oxygen to the body cells for producing more energy or by the rapid breakdown of food needed for doing physical exercise etc.

Here, all these statements are correct. Hence, your answer will be option [D].

Here, all these statements are correct. Hence, your answer will be option [D].

Here, all these statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence your answer will be option [D].

The breathing rate in children is higher than that of adults. Children breathe about 20 to 30 times per minute.

Yeast is single-celled organisms that respires anaerobically producing alcohol and carbon dioxide. Glucose + No oxygen (Anaerobic respiration in yeast)  Alcohol + CO2 + Energy The alcohol is used in wine and beer industry, while the CO2 is used in bread making.

Here, all the statements are correct. Hence your answer will be option [D].

Test tube (A) contains a snail in water. The snail will use of oxygen for respiration and produce carbon dioxide. Test tube (B) contains a “water plant” in water. The water plant will do photosynthesis by using carbon dioxide and water and produce oxygen. The water plant will use some of this oxygen for respiration and produce carbon dioxide. This carbon dioxide will then be used by the plant in photosynthesis. Test tube (C) contains both, a snail and a water plant. The carbon dioxide produced by the respiration is snail will be all used up by the water plant in photosynthesis. We conclude that the test tube containing only snail will have the highest concentration of CO2 because there is no plants to use up the carbon dioxide produced during the respiration in snail.