Question

Q.7. Give reasons for the foowing:
(a) Arteries are thick walled.
(b) Blood goes only once in one cycle through the heart in fishes.
(c) Plants have low energy needs.
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Answer 1

Answer:

a) because they flow is very fast

b) because there is only one chambered heart

c) because they do not have to work and make there own food with the help of photosynthesis and release oxygen

Answer 2

Answer:

arteries are thick walled to enable them to withstand the high pressure of blood ejected from the heart  pushing the blood out . plants have lower energy needs as compared to animals because they do not move.in a large plant there are many dead cells like sclerenchyma because of which they need less energy.

Explanation: