Solved examples for class 7 science : Chapter 10

    Respiration in Organisms

    I. Multiple Choice Questions (MCQs).
    Q.1. All the organisms get energy through the process of
    a) respiration
    b) egestion
    c) transportation
    d) none of these

    Answer (a) respiration
    Q.2. Breathing is also called
    a) internal respiration
    b) cellular respiration
    c) external respiration
    d) all of these
    Answer: (c) external respiration
    Q.3. The double membranous layer that surrounds lungs is called
    a) alveoli
    b) bronchi
    c) pleura
    d) epiglottis
    Answer: c) pleura
    Q.4. An acid that accumulates in the muscles and causes cramps after heavy exercise, is
    a) formic acid
    b) citric acid
    c) tartaric acid
    d) lactic acid
    Answer: (d) lactic acid
    Q.5. An organ that is used by earthworms, leeches and frogs (under water) for the exchange of gases, is
    a) moist skin
    b) spiracles
    c) gills
    d) none of these

    Answer: a) moist skin

    II. Fill in the blanks by selecting appropriate words from the given list:
    List : downward, energy, chest cavity, breathing rate, fermentation
    Q.1. The anaeorbic respiration is also known as ______________ when it is carried out by yeast to produce alcohol.
    Q.2. In human, lungs are present in ______________.
    Q.3. The number of times a person breathes in a minute is called his ___________.
    Q.4. During inhalation, ribs move outwards while diaphragm moves ___________.
    Q.5. Like other living organisms plants also respire to get ______________ from the food.

    Answer:
    1- fermentation,
    2- chest,
    3- breathing rate,
    4- chest cavity,
    5- energy
    III. Match the items of Column A with those of Column B.

    Answer: 1-(b), 2- (d), 3- (e), 4-(a), 5-(c)

    IV. Write ‘T’ for the true and ‘F’ for the false statements.
    Q.1. All the organisms including plants, animals and microorganisms need energy.
    Q.2. Different animals have different organs for taking in oxygen and giving out carbon dioxide.
    Q.3. In aquatic animals like fishes and tadpoles, spiracles are the breathing organs.
    Q.4. In humans both lungs are surrounded by a double membranous layer called pleura.
    Q.5. Plants use oxygen and give out carbon dioxide only during the day.
    Answer: – 1-T, 2-T, 3-F, 4-T, 5- F
    V. Very Short Answer Questions.

    Q.1. Give the composition of O2 and CO2 in inhaled as well as exhaled air.
    Answer: The taking in of the air rich in oxygen into the body is called inhalation and giving out of air rich in carbon dioxide is called exhalation.

    Q.2. How do the organisms get energy?
    Answer: All the organisms get energy through respiration.

    Q.3. Why do all the organisms need energy?
    Answer: All living organisms perform many activities such as movement, locomotion, growth, reproduction, etc., and for these activities require energy.

    Q.4. When does anaerobic respiration occur in our body?
    Answer: Anaerobic respiration takes place in the absence of oxygen.

    Q.5. How does exchange of gases occur in unicellular organisms?
    Answer: In unicellular organisms like Ameoba and Paramecium, exchange of gases occur by diffusion through their body surface.

    VI. Short Answer Questions.
    Q.1. How does exchange of gases occur in whales and dolphins?
    Answer: Whales and dolphins live in water. They have lungs which can take in oxygen only from the air because of this, they have to come on the surface of water to breathe. They breathe through a blowhole present on their head.

    Q.2. How does respiration occur in insects?
    Answer: Insects have a network of air tubes called trachea that helps in gaseous exchange. Oxygen rich air rushes through spirales into tracheal tube and diffuses into the body tissues. Now, this oxygen-rich air reaches to every cell of the body. Similarly, carbon dioxide from the cells goes into the tracheal tubes and moves out through spiracles.

    Q.3. Differentiate between breathing and respiration.
    Answer: Following are the differences between breathing and respiration

    Q.4. Name the kinds of respiration and explain each one in brief.
    Answer: Depending on the presence or absence of oxygen, respiration is of two types :

    (i) Aerobic Respiration – When break down of food (glucose) takes place in the presence of oxygen, carbon dioxide and water are formed with a release of energy.
    (ii) Anaerobic respiration-When the break down of food takes place in the absence of oxygen and release very small amounts of energy.

    Q.5. Differentiate between aerobic and anaerobic respiration.
    Answer:

    Q.6. How can you say that different animals have different methods for exchange of gases?
    Answer:
    • In unicellular organisms like Ameoba and Paramecium, exchange of gases occur by diffusion through their body surface.
    • Earthworms, Leeches and frog (under water) use their moist skin for the exchange of gases.
    • In insects like cockroaches and grasshoppers many small pores are present on their lateral sides of the body. These pores are called spiracles.
    • Insects have a network of air tubes called trachea that helps in gaseous exchange.

    Thus we can see that the different animals have different methods for taking in oxygen and giving out carbon dioxide.

    VII. Long Answer Questions.
    Q.1. Describe respiratory system of human beings with the help of a well-labelled diagram. Also explain main organs of respiratory system.
    Answer: In humans, a special system is present that helps in taking in oxygen and giving out carbon dioxide. This system is called respiratory system.

    Main organs of respiratory system are:-
    (a) Nasal Cavity: Air enters the nasal cavity through nostrils. Hair present inside the nasal cavity filter the air by trapping the dust particles and germs present in air.

    (b) Trachea (wind pipe): It is a tube like structure that allows the air to enter in the lungs. (c) Bronchi: Trachea branches into two tubes which are called bronchi. These bronchi enter into Lungs.

    (d) Lungs: Lungs are present in chest cavity. These are two in numbers. Each lung is surrounded by a double membranous layer called pleura. Inside each lung the bronchus branches in smaller tubes called bronchioles. Each bronchiole terminates in a sac like structure called alveoli. Each alveolus is surrounded by a network of blood capillaries.

    Q.2. (a) What do you mean by breathing in humans? Also explain the mechanism of breathing.
    (b) How will you demonstrate the role of diaphragm in breathing?

    Answer: (a) Breathing involves taking in oxygen and giving out air rich in carbon dioxide with the help of respiratory organs. The taking in of the air rich in oxygen into the body is called inhalation and giving out of air rich in carbon dioxide is called exhalation.

    Mechanism of breathing: Breathing involves movement of rib cage and diaphragm.
    During inhalation ribs move outwards and upwards while diaphragm moves downward. Hence, the size of the chest cavity increases. The air pressure inside the lungs decreases, while the atmospheric pressure increases. Now air rushes into lungs from the outside and lungs get filled with air.

    During exhalation, the ribs move inward and downward while diaphragm moves upward to its former position. This reduces the size of chest cavity. So, the air pressure increases in the lungs while atmospheric pressure decreases and air is pushed out of the lungs.

    b) To demonstrate the role of diaphragm in breathing we need a transparent plastic bottle, balloon, straw, bubblegum.

    Procedure : Cut off the bottom of a transparent plastic bottle. Make a hole through the cap.
    Attach a balloon to a straw and pass this straw through the hole present in cap. Use bubblegum to fix this straw in the cap. Stretch a rubber sheet or balloon across the cut end of the bottle. Pull this balloon or rubber sheet down and then push it up. Observation : Pulling of the rubber sheet down result in filling up the balloon with air and pushing of the rubber sheet causes deflation of balloon.

    Q.3. Describe respiration in plants with the help of a suitable diagram.
    Answer: Plants take in oxygen and release carbon dioxide by the process of respiration. But in a plant, each part can independently exchange gases from their surroundings. In green parts of the plant, special pores are present that help in exchange of gases. These pores are called stomata. But in non-green plants instead of stomata Lenticels are present that help in exchange of gases. The shoot, the part above the ground, of a plant takes oxygen from atmosphere but underground parts as roots take oxygen from the air spaces present between the soil particles.

                                                    

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