The part of the leaf of a terrestrial plant on which stomatal opening is seen:

The water proof layer that protects human skin.

Percentage of oxygen present in the atmosphere.

The branchioles end in millions of tiny interconnected cavities called:

Give an example of small organism in which the ratio of surface area to volume is high.

Guard cells become turgid by actively transporting which of the following ions ?

Carbon dioxide and oxygen diffuse in and out of leaves through small openings called:

Write the name of the process of stomatal opening and closure.

The most numerous cells in the epithelium of the bronchus and bronchioles are called:

The respiratory system of insects is called: