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.

Cockroaches breathe with the help of air tubes called “tracheae”. Cockroach has spiracles on the sides of its body and trachea or air tube throughout inside its body for the process of breathing and respiration.

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.

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.

The fish lives in water and uses the oxygen dissolved in water for breathing. Since the amount of oxygen dissolved in water is low as compared to the amount of oxygen in air on land, therefore, the rate of breathing is much higher in fish than the land animals like man, dog and sparrow. A higher rate of breathing provides more oxygen to fish from water.

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.

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

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

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.

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

The fish has special organs of breathing called “gills”. The gills help the fish to use oxygen which is dissolved in water. Gills are projections of the skin. Gills have blood vessels for the exchange of respiratory gases as oxygen and carbon dioxide.

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.

All the organisms which obtain energy by anaerobic respiration can live without the oxygen. Yeast is an organism which can live without oxygen of air because it obtains energy by the process of anaerobic respiration. Those organisms which obtain energy by the process of an aerobic respiration are called anaerobes. Yeast is an anaerobe. It can survive in the absence of oxygen and converts glucose into alcohol. Therefore, it used in wine industry to make alcohol.

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

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.

The breathing is a physical process while cellular respiration is a bio-chemical process.

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

During exhalation, ribs moves down and inwards, while diaphragm move upwards and relaxes. This reduces the size of the chest cavity and air is pushed out of the lungs.

Smoking destroys the lung tissue gradually due to which breathing becomes very difficult. Smoking also damages the health of non-smokers who inhale the air containing tobacco smoke. And smoking kills gradually. Many people die every year from disease caused by smoking. The bad habit of smoking must be avoided to lead a healthy life.

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

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].

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.