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Respiration In Organisms

Class 7th Science CBSE Solution

Exercise
Question 1.

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


Answer:

When an athlete runs, he or she losses a lot of energy. To get more energy, he/she breathes faster and deeper than usual for the faster breakdown of food to release energy because an athlete needs to supply more energy to make muscle cells to do work at a much higher rate than normal.


Question 2.

List the similarities and differences between the aerobics and anaerobic respiration.


Answer:

Similarity

(i) In both the types of respiration, the energy released.

(ii) In both the types of respiration, carbon dioxide produced.

Differences:


Question 3.

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


Answer:

Sneezing removes the foreign particle like dust , smoke , pollen etc from the inhaled air , thus ensuring good air quality inside our body.

When dust laden air is inhaled, the dust particles get trapped in the nasal hair and irritate the inner lining of the nostril cavity which is lined by nasal hair and remains wet due to mucus secretion.

This causes sneezing as a result of which the dust particles are expelled and clean air enters our body.





Question 4.

Take three test-tubes. Fill 3/4th of each with water. Label them A, B and C. Keep a snail in the 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?


Answer:

Tube A: Only snail.

Tube B: Only water plant.

Tube C: Snail + Water Plant.


Test-tube C would have the highest concentration of carbon dioxide (CO2).

Test tube A would have the highest concentration of carbon dioxide (CO2) because test tube A contains snail that exhales CO2

Test tube B contains a plant which takes in CO2 for photosynthesis and gives out O2. Hence, more O2 concentration found in test tube B.

Test tube C contains both a water plant and a snail. Snail release CO2 which gets used up by the plant, Hence less CO2 concentration than tube A

the concentration of CO2test tube A > C > B. Hence test tube A has a max concentration of CO2.


Question 5.

In cockroaches, air enters the body through
(i) lungs (ii) gills
(iii) spiracles (iv) skin


Answer:

A cockroach has small openings called spiracles on the sides of its body (see the picture attached).

Oxygen-rich air rushes through spiracles into the tracheal tubes, diffuses into the body tissue, and reaches every cell of the body.


Question 6.

During heavy exercise, we get cramps in the legs due to the accumulation of
(i) carbon dioxide (ii) lactic acid
(iii) alcohol (iv) water


Answer:

During vigorous physical exercise, anaerobic respiration takes place in human muscles because oxygen is used faster in the muscles compared to its supply by the blood. Thus, sudden buildup of lactic acid poison our muscles and cause muscular cramps.


Question 7.

Normal range of breathing rate per minute in an average adult person at rest is:
(i) 9-12 (ii) 15-18
(iii) 21-24 (iv) 30-33


Answer:

Correct option: (ii) 15-18
Normal range of breathing rate per minute in an average adult person at rest is 15-18.


Question 8.

During exhalation, the ribs
(i) move outwards
(ii) move downwards
(iii) move upwards
(iv) do not move at all


Answer:

(ii) move downwards

During exhalation, ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the chest cavity and air is pushed out of the lungs.


Question 9.

Match the items in column I with those in column II.


Answer:

(a)-(iii), (b)-(iv), (c)-(i), (d)-(v), (e)-(ii), f(vi).


Yeast : Alcohol


Yeast get energy through anaerobic respiration. They are known as anaerobes. In the absence of oxygen, glucose breaks down into alcohol and carbon dioxide.


Diaphragm : Chest cavity


A large, muscular sheet called diaphragm forms diaphragm the floor of the chest cavity. The movement of the diaphragm and the rib cage are involved in the breathing.


Skin : Earthworm


The skin of earthworm is moist and slimy through which they respire.


Leaves : Stomata


The leaves of the plants have tiny pores called stomata for exchange of oxygen and carbon dioxide.


Fish : Gills


Fishes respire through gills. Gills are projections of the skin.


Frog : Lungs and skin


Frogs have pair of lungs for respiration, they also respire through their skin which is moist and slippery.


Question 10.

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

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

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

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

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

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


Answer:

(i) False.


During heavy exercise, we breathe faster and deeper than usual for faster breakdown of food to release energy.


(ii) False.


Photosynthesis doesn’t take place at night whereas respiration occurs in plants throughout the day and night.


(iii) True.


Though frogs have pair of lungs like human beings, they can also breathe through their skin, which is moist and slippery.


(iv) False.


Fishes do not have lungs. In fishes, gaseous exchange takes place through gills.


(v) True.


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.



Question 11.

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

(i) The air tubes of insects.

(ii) Skeletal structures surrounding chest cavity

(iii) Muscular floor of chest cavity

(iv) Tiny pores on the surface of leaf.

(v) Small openings on the sides of the body of an insects

(vi) The respiratory organs of human beings

(vii) The openings through which we inhale

(viii) An anaerobic organism

(ix) An organism with tracheal system


Answer:



Question 12.

The mountaineers carry oxygen with them because:

(a) At an altitude of more than 5 km there is no air.

(b) The amount of air available to a person is less than that available on the ground.

(c) The temperature of air is higher than on the ground.

(d) The pressure of air is higher than that on the ground.


Answer:

The mountaineers carry oxygen with them because the amount of oxygen availability to a person is less than that availability on the ground.