Question

Give reason for the following
A) arteries are thick walled
B) blood goes only once in one cycle through the heart in fishes
C) plants have low energy needs

Answer 1

(a) Since arteries have to carry blood from heart to distant body parts, blood flows in them with a very high pressure. To sustain this high pressure arteries are thick walled.

(b) Heart of fishes has 1 atrium and 1 ventricle. So, they have single circulation system i.e. the heart receives deoxygenated blood into the atrium and pumps oxygenated blood through veins to the gills. Therefore in fishes blood only passes once through the heart.

(c) Plants are the primary producers in our ecosystem i.e. they receive energy directly from sun and only 10% of this energy is passed from one trophic level to the next which means plants have much more energy than others down the trophic level. Also, plants produce their own food which means they don’t need energy to gather food and digest it. Additionally plants are static and don’t need energy for locomotion. Because of all these reasons plants have low energy needs.

Answer 2

A) because the pressure of blood flowing through the arteries is more