Science STD 7 Chapter 6: Respiration in Organisms - Exercises

Science STD 7 Chapter 6: Respiration in Organisms - Exercises

1. Why does an athlete breathe faster and deeper than usual after finishing the race?

During a race, an athlete's body needs more energy. To produce this extra energy, the body requires more oxygen. When the athlete finishes the race, the body's cells are temporarily deficient in oxygen. To compensate for this oxygen debt and to break down the lactic acid produced during anaerobic respiration, the athlete breathes faster and deeper. This increases the supply of oxygen to the cells, leading to a complete breakdown of food and the release of more energy.

2. List the similarities and differences between aerobic and anaerobic respiration.

Similarities Differences
Both are processes by which organisms get energy from food. Aerobic respiration occurs in the presence of oxygen, while anaerobic respiration occurs without oxygen.
Both involve the breakdown of glucose. Aerobic respiration produces carbon dioxide, water, and a large amount of energy. Anaerobic respiration produces alcohol (in yeast) or lactic acid (in muscles) and a small amount of energy.
Both occur in living cells. Aerobic respiration is more common in most organisms. Anaerobic respiration is common in organisms like yeast or in muscle cells during strenuous exercise.

3. Why do we often sneeze when we inhale a lot of dust-laden air?

We often sneeze when we inhale dust-laden air because the dust particles irritate the lining of our nasal cavity. Sneezing is a reflex action that forcefully expels these foreign particles from the inhaled air, ensuring that only clean air enters the lungs. This protects our respiratory system from foreign particles.

4. Take three test-tubes. Fill 3/4th of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO₂?

Test tube **A** will have the highest concentration of $CO_2$. This is because the snail in test tube A will be performing respiration, taking in oxygen and releasing carbon dioxide, without any plant to absorb the carbon dioxide. In test tube B, the plant will use $CO_2$ for photosynthesis. In test tube C, the plant and snail will balance each other's gas exchange, keeping the concentration of $CO_2$ lower than in test tube A.

5. Tick the correct answer:

  1. (a) In cockroaches, air enters the body through
    1. lungs
    2. gills
    3. spiracles
    4. skin
  2. (b) During heavy exercise, we get cramps in the legs due to the accumulation of
    1. carbon dioxide
    2. lactic acid
    3. alcohol
    4. water
  3. (c) Normal range of breathing rate per minute in an average adult person at rest is:
    1. 9-12
    2. 15-18
    3. 21-24
    4. 30-33
  4. (d) During exhalation, the ribs
    1. move outwards
    2. move downwards
    3. move upwards
    4. do not move at all

6. Match the items in Column I with those in Column II:

Column I Column II
(a) Yeast (iii) Alcohol
(b) Diaphragm (iv) Chest cavity
(c) Skin (i) Earthworm
(d) Leaves (v) Stomata
(e) Fish (ii) Gills
(f) Frog (vi) Lungs and skin

7. Mark T if the statement is true and 'F' if it is false:

  1. (i) During heavy exercise the breathing rate of a person slows down. (T/F)

    F

  2. (ii) Plants carry out photosynthesis only during the day and respiration only at night. (T/F)

    F

  3. (iii) Frogs breathe through their skins as well as their lungs. (T/F)

    T

  4. (iv) The fishes have lungs for respiration. (T/F)

    F

  5. (v) The size of the chest cavity increases during inhalation. (T/F)

    T

8. Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

[Image of the word search puzzle]

  1. (i) The air tubes of insects

    TRACHEAE

  2. (ii) Skeletal structures surrounding chest cavity

    RIBS

  3. (iii) Muscular floor of chest cavity

    DIAPHRAGM

  4. (iv) Tiny pores on the surface of leaf

    STOMATA

  5. (v) Small openings on the sides of the body of an insect

    SPIRACLES

  6. (vi) The respiratory organs of human beings

    LUNGS

  7. (vii) The openings through which we inhale

    NOSTRILS

  8. (viii) An anaerobic organism

    YEAST

  9. (ix) An organism with tracheal system

    INSECT

9. The mountaineers carry oxygen with them because:

  1. At an altitude of more than 5 km there is no air.
  2. The amount of air available to a person is less than that available on the ground.
  3. The temperature of air is higher than that on the ground.
  4. The pressure of air is higher than that on the ground.

Suggested Activities and Projects

1. Observe fish in an aquarium. You will find flap like structures on both sides of their heads. These are flaps which cover the gills. These flaps open and close alternately. On the basis of these observations, explain the process of respiration in the fish.

Outline: This activity aims to help you understand how fish breathe. The flapping movement of the flaps covering the gills allows water to pass over the gills. The fish takes in water through its mouth and forces it out over the gills. Gills are well-supplied with blood vessels, which facilitates the exchange of gases. Oxygen dissolved in the water is absorbed into the blood, while carbon dioxide is released from the blood into the water.

2. Visit a local doctor. Learn about the harmful effects of smoking. You can also collect material on this topic from other sources. You can seek help of your teacher or parents. Find out the percentage of people of your area who smoke. If you have a smoker in your family, confront him with the material that you have collected.

Outline: This project focuses on raising awareness about the dangers of smoking. You would research the harmful effects, such as lung damage and cancer, and present this information. You would also conduct a small survey in your area to find the percentage of smokers and discuss the negative effects with a family member who smokes, encouraging them to quit.

3. Visit a doctor. Find out about artificial respiration. Ask the doctor: (a) When does a person need artificial respiration? (b) Does the person need to be kept on artificial respiration temporarily or permanently? (c) From where can the person get supply of oxygen for artificial respiration?

Outline: This activity is about understanding artificial respiration. A doctor would explain that a person needs artificial respiration when they are unable to breathe on their own, such as during a medical emergency. The need can be temporary (e.g., during surgery) or permanent (e.g., in cases of severe lung damage). The oxygen supply for artificial respiration comes from oxygen cylinders or a medical-grade oxygen concentrator.

4. Measure the breathing rate of the members of your family and some of your friends. Investigate: (c) If the breathing rate of children is different from that of adults. (d) If the breathing rate of males is different from that of females. If there is a difference in any of these cases, try to find the reason.

Outline: This project involves collecting and analysing data on breathing rates. You would measure the breathing rate of family members and friends and observe the differences. Children generally have a higher breathing rate than adults because their bodies need more energy for growth. While there can be minor variations, there is generally no significant difference in the resting breathing rates of males and females.