During respiration,the exchange of gases takes place in:

Why do veins have thin walls as compared to arteries?

What is common for $Cuscuta$,ticks,and leeches?

Kidneys are located in the thoracic cavity, one on either side of the backbone.

$(a)$ Name the following:
$(i)$ Part where air is filtered by fine hair and mucus.
$(ii)$ Part which terminates in balloon-like structures.
$(iii)$ Balloon-like structures where exchange of gases takes place.
$(iv)$ Part which separates the chest cavity from the abdominal cavity.
$(b)$ Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?

Draw the diagram of the alimentary canal of a human and label the following parts:
Mouth,Oesophagus,Stomach,Intestine.