Class 7 Science Chapter 6 MCQ

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

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]

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.

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.

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.

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

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]

Here, all these statements are correct told by Paheli. 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.

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.

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

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].

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.

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.

During heavy exercise, anaerobic respiration takes place in our muscle cells. This happens as the oxygen gets used up faster in our muscle cells then can be supplied by the blood. To produce extra energy for exercise, the muscle cells shift to anaerobic respiration. Glucose + No oxygen (in muscles, anaerobic respiration)  Lactic acid + Energy