Basic Science Solutions for Class 7 Science Chapter 11 Respiration In Plants And Animals are provided here with simple step-by-step explanations. These solutions for Respiration In Plants And Animals are extremely popular among Class 7 students for Science Respiration In Plants And Animals Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Basic Science Book of Class 7 Science Chapter 11 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Basic Science Solutions. All Basic Science Solutions for class Class 7 Science are prepared by experts and are 100% accurate.

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Earthworms do not have any special organ for breathing. They use their skin to breathe.

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Insects have openings on the sides of their body called spiracles, through which they inhale air. The inhaled air gets distributed throughout the insect's body through the network of trachea.

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The number of times we breathe air in and out in a minute can be defined as the rate of respiration.

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In the leaves of plants, various small openings, called stomata, are present. Plants exchange gases through these openings.  

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Loosening of soil causes the gaps between soil particles to enlarge, which helps in the easy exchange of gases between the atmosphere and the roots of plants, which also breathe.

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Strenuous activities, such as running, swimming and dancing, require a huge amount of oxygen. When this demand of oxygen is not fulfilled, the muscles start respiring anaerobically.

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The hair and nasal membrane present in the nasal cavity perform the following functions.
• They purify the air entering the nose.
• They moisten the air.
• They regulate the temperature of the air.

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Tadpoles and fish have to utilise the oxygen dissolved in water. They have organs called gills for this purpose. The gills have several filaments supplied with numerous capillaries. Water enters through the mouth of a fish or a tadpole and flows over the filaments of the gills. The oxygen dissolved in the water diffuses into the capillaries and the carbon dioxide in the capillaries is released into the water.  

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The rate of respiration increases after exercise because, when we are engaged in strenuous activities, our body utilises much more energy than usual. This requirement of a higher amount of energy during exercise is met by an increase in the respiration rate, which increases the amount of oxygen made available to the body.

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Following are the steps involved in respiration:

(a) External respiration: Inhalation of oxygen by an organism from the atmosphere and exhalation of carbon dioxide back to the atmosphere is termed external respiration.

(b) Internal respiration: Internal respiration refers to breaking down of glucose by oxygen in all the cells of the body.  Oxygen, from the respiratory organs of an organism, is distributed to all the cells of the body of the organism where it breaks down glucose to release energy.

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The type of respiration in which there is no requirement of oxygen is called anaerobic respiration. It occurs mostly in microbes. During anaerobic respiration, products such as lactic acid and alcohol are produced.

                 Glucose        Ethanol + CO2 + ATP (Energy)
                 Glucose       Lactic acid + ATP (Energy)

Anaerobic respiration in microbes is utilized in the industrial production of lactic acid and alcohol.
We make use of this process to provide instant energy to muscle cells during strenuous activities such as running, swimming etc., when the amount of oxygen in our body becomes insufficient to perform aerobic respiration.

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Take two transparent glasses and fill them half with water. In both glasses, add lime powder and cover them with cardboard pieces. Make two holes in each cardboard piece and insert straws in all the four holes. Mark the straws 1, 2, 3 and 4. Straws 2 and 4 should be placed in such a way that they remain suspended in the air in half-filled glasses and do not touch the water surface.
Now, inhale from straw 2 using your mouth and exhale into the other glass using straw 3. Limewater in the second glass, into which air has been exhaled, turns milky because of the presence of a larger amount of CO2 in the exhaled air. This shows that exhaled air contains carbon dioxide.

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The path of air from the nose to the lungs is described below.
• Air from the atmosphere is inhaled through the two openings in the nose called nostrils.
• The nostrils lead the air to the nasal passage or nasal cavity. The nasal cavity contains numerous nasal hair and mucus membranes. These hair filter the air we inhale by trapping the dust particles that enter the nose along with the air.
• The nasal cavity leads this filtered air to the pharynx that finally leads the air to the windpipe or trachea through the larynx.
• The larynx is also called the voice box, as it is responsible for the generation of speech.
• The trachea leads the air to the lungs through a pair of bronchi. 

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Our body has a circular, dome-like muscle present right below the lungs. This muscle is called the diaphragm. The diaphragm acts like a pump to create a vacuum in our chest cavity. When we inhale, the diaphragm gets flattened, and at the same time, the ribcage moves upward and outward. This leads to an increase in the volume of our thoracic/chest cavity. As the volume increases, the pressure of air outside the lungs increases and air rushes into our lungs through our nostrils.

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Oxygen enters our lungs from the atmosphere through the nose. In the lungs, millions of balloon-like structures, called alveoli, are present. Air from bronchioles reaches these alveoli, which are surrounded by a very fine mesh of capillaries. These capillaries have very thin walls that allow oxygen to diffuse into the blood from each alveolus. Haemoglobin present in the red blood cells of blood combines with oxygen and is carried to each cell of the body through blood.

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1. Oxygen combines with haemoglobin in the blood to form oxyhaemoglobin.
2. The lungs have millions of air sacs called alveoli.
3. Carbon dioxide and water are formed during internal respiration.
4. Anaerobic respiration is also known as fermentation.
5. The larynx is responsible for speech.
6. The tiny openings on stems and fruits that plants use for breathing are called stomata.
7. Alcohol is formed during anaerobic respiration.
8. The opening and closing of the stomata are controlled by guard cells.



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