$(a)$ 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) $(a) (i)$ Herbivores,which consume grass,possess a longer small intestine to facilitate the digestion of cellulose. Cellulose is a complex carbohydrate that requires more time to break down,necessitating a longer transit time within the digestive tract.
$(a) (ii)$ Carnivores,which consume meat,have a shorter small intestine because meat is protein-rich and relatively easy to digest,requiring less time for nutrient absorption.
$(b) (i)$ Within the lungs,the trachea branches into smaller tubes called bronchi and bronchioles,which terminate in numerous balloon-like structures known as alveoli. These alveoli are surrounded by an extensive network of blood capillaries,providing a massive surface area for the efficient diffusion of gases.
$(b) (ii)$ The concentration of dissolved oxygen in water is significantly lower than the concentration of oxygen in the atmosphere. Consequently,aquatic organisms,such as fish,must pump water through their gills at a much higher rate to extract sufficient oxygen for their metabolic needs.