Paheli Boojho Chapter 10 Class 7 science Respiration in Organisms:
Boojho noticed that when he released his breath after holding it for some time, he had to breathe heavily. Can you tell him why it was so?
Every animal breaths. The rate of breathing is fixed in every such organism. When we hold our breath for a few moments oxygen content decreases in our body. To compensate for this when we open mouths we breathe heavily.
Paheli wants to know why we yawn when we are sleepy or drowsy.
Our body has great feedback control. During sleepiness and drowsiness oxygen level in the body is lesser. Yawning brings more oxygen and compensate oxygen level.
Fact: Yawning increases the amount of oxygen in the brain. So, this is good for the brain and increases mental alertness.
Boojho wants to know how much air a person can hold in the lungs?
Answer: It is the maximum air that we can exhale after forceful inhalation and some air that still remain in the lung. It is about 6ltr.
Boojho wants to know if cockroaches, snails, fish, earthworms, ants and mosquitoes also have lungs
Answer: All animals including fishes, snails, earthworms etc need oxygen. Different organisms may have different mechanisms for oxygen intake and out i.e. different respiratory mechanisms.
Cockroaches have tracheal tubes inside the body. They do not breathe but exchange the air from these tubes.
Similarly, Snail respires through its surface; Fishes have gills that filter oxygen from water. Earthworm respires through their wet skin. Ants and mosquitos have respiratory systems similar to cockroaches and respire through such tubes.
Fact: Cockroaches, ants and mosquitos belong to a similar group of animals which we call Insects. So, they have similar mechanisms.
Boojho has seen in television programmes that whales and dolphins often come up to the water surface. They even release a fountain of water sometimes while moving upwards. Why do they do so?
Whales and dolphins are advanced animals. They have lungs like us. They come to the top of water surface and brings in the air through its top hole. The fountain we see is the water whales push to remove the water from the hole.
Paheli wants to know whether roots, which are underground also take in oxygen? If so, how?
Roots also need oxygen. They fulfil this requirement from the air spaces between the soil particles.
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