Question

Give reason- 1) Arteries are thick walled. 2) veins have valve 3)Blood goes only once in one cycle through the hesrt in fishes. 4) Plants have low energy needs as compared to animals.

Answer 1

artries are thick walled because blood pressure is high in artries

in veins valves are present because the blood does not flow in another direction

blood goes once in heart of fishes because their blood is oxegenated from gills and directly sent to different body parts