Which one of the following is the by-product gas of photosynthesising ?

The branchioles end in millions of tiny interconnected cavities called:

Large amount of water vapour are lost from leaves by which of the following process?

Insects have a protective layer that covers their skin called:

The respiratory system of insects is called:

The water proof layer that protects human skin.

Percentage of oxygen present in the atmosphere.

Name the openings in the respiratory system of insects.

Which part of the organism across around which the gas exchange takes place ?

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