(a) What is meant by aquatic animals and terrestrial animals?
(b) From where do the aquatic animals and terrestrial animals obtain oxygen for breathing and respiration?

(a) Terrestrial animals live on land. They respire through lungs. Examples of terrestrial animals are human beings, cows, cats, dogs, etc.
Aquatic animals live in water. They have a special organ for respiration. They are called gills. An example of aquatic animals is fish.
(b) Aquatic animals obtain the oxygen dissolved in water for breathing and respiration. Terrestrial animals obtain oxygen present in air for breathing and respiration.