Give biological reasons for the following :

Throat infections can lead to ear infections.

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 :

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.