The diagram given below represents the human heart in one phase of its functional activities. Study the same and answer the questions that follow:

(i) Name the phase.

(ii) Label the parts 1, 2, and 3

(iii) Which part of the heart is contracting in this phase? Give a reason to support your answer.

(iv) Draw well labelled diagrams of part 1 and 2 to show the structural differences between them.

Give biological reasons for the following :

Throat infections can lead to ear infections.

Give biological reasons for the following :

The wall of the ventricle is thicker than the auricles.

Give biological reasons for the following :

Wooden frames of doors get jammed during the monsoon season.