When we breathe out,why does the air passage not collapse?

Name the process of loss of water in the form of vapour from the aerial parts of the plants.

Single circulation,i.e.,blood flows through the heart only once during one cycle of passage through the body,is exhibited by:

$(a)$ State the reason for the following:
$(i)$ Herbivores need a longer small intestine,while carnivores have a shorter small intestine.
$(ii)$ The lungs in human beings are designed to maximize the area for the exchange of gases.
$(b)$ The rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

$(a)$ State two functions of bile juice.
$(b)$ Differentiate between the functions of enzymes pepsin and trypsin.

During deficiency of oxygen in tissues of human beings,pyruvic acid is converted into lactic acid in the