NCERT Science Class 7, Respiration in Organisms | Solutions of CBSE Sample questions following CCE scheme


CBSE Board, Class 7
NCERT Science - Respiration in Organisms
CBSE Sample Questions with Solutions (Following latest CCE scheme of examinations) 
Q.1: Why we get muscle cramps after heavy exercise?
Solution: During heavy exercise the demand for energy is high. But the supply of oxygen to produce energy is limited. Then anaerobic respiration takes place in the muscle cells to fulfill the demand of energy.

Glucose  in absence of oxygen > Lactic Acid + Energy

The cramps occur only when the muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps. 

Q.2: Why we feel hungry after a physical activity?
Solution: During a physical activity we need more energy. Whenever a person needs extra energy he/she breathes faster. As a result, more oxygen is supplied to our cells. It speeds up the breakdown of food and more energy is released. Due to rapid breakdown of food we feel hungry.

Q.3: How does the exchange of gases occur in breathing?
Solution: When we inhale air it passes through our nostrils to nasal cavity. From nasal cavity the air reaches our lungs. The exhaled air follows same route to go out. Breathing in and out involves the movement of the diaphragm and the rib cage.

Q.4: Write short notes on -
     (i)        Inhalation and Exhalation
    (ii)        Gills
     (i) Inhalation: The process of taking in of air rich in oxygen into the body is called ‘inhalation’. During inhalation, ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs. Exhalation: The process of giving out of air giving out of air rich in carbon dioxide is known as ‘exhalation’. During exhalation, ribs move down and inwards while, diaphragm moves up to its former position. This movement reduces the size of our chest cavity and air is pushed out.
    (ii)      Gills: Gills in fish help them to use oxygen dissolved in water and thus, help them in breathing. Gills are projections of their skin. These are well supplied with blood vessels for exchange of gases.  

Q.5: Do the plants also respire?
Solution: Like all other organisms, plants also respire for their survival. They take oxygen from the air and give out carbon dioxide. In the cells oxygen is used to breakdown glucose into carbon dioxide and water as in other organisms.

Q.6: How do the plants breathe in oxygen?
Solution: In plants each part can independently take in oxygen from air and give out carbon dioxide. Leaves of the plants have tiny pores called ‘stomata’ for exchange of oxygen and carbon dioxide. Roots take up air from the pores (air spaces) present between the soil particles.  

Objective Questions / Short Questions
Q.1: Fill in the blanks:
       (a)       Breathing is a part of ________.
       (b)       The food has _______ which is released during _____.
       (c)       Yeasts can survive in the absence of air. They are called ________.
       (d)       All living organisms ________ to get energy from food.
       (e)       ________ are used in wine, beer industry and bakery.
        (f)       Blood in our body is oxygenated by the organ known as ________.
       (g)       Breathing rate in human beings in normal condition is ________ times in a minute.
       (h)       The site of cellular respiration is ________.
         (i)       Cockroach breath through _________.
        (j)       Earthworms breathe through their _________.
       (k)       The process of breakdown of food in the cell with the release of energy is called ____________.
Solution: (a) respiration (b) stored energy, respiration (c) anaerobes (d) respire (e) yeasts (f) lungs (g) 15-18 (h) mitochondria (i) spiracles (j) skin (k) cellular respiration.

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