Give reasons for the following:
(a) Arteries are thick walled.
(b) Blood goes only once through the heart in fishes.
(c ) Plants have low energy needs.

Explain : Blood goes only once through the heart in fishes.

Which of the following statements are true? 1) Arteries have thick walls. 2) Arteries carry blood from heart to body parts. 3) Arteries have low blood pressure. 4) Pulmonary artery carries Oxygenated blood.

How can you explain the following ? (i) Auricles have thinner walls than ventricles. (ii) Blood flows under pressure in the arteries. (iii) Heart has striped muscles unlike other viscera. (iv) There is a slight gap between auricular systole and ventricular systole.

Give reasons for the following : (i) The muscular walls of ventricles are thicker than the walls of atria. (ii) Arteries have thick elastic walls.

Give reasons for the following: (i) Binary compounds of oxygen and fluorine are called fluorides. (ii) Fluorine forms only one oxoacid HOF. (iii) Noble gases have very low melting and boiling points.

Give the technical terms used for the following: Blood passes twice through the heart to supply once to the body.