Which of the following statement$(s)$ is/are true about the heart?

$(a)$ Name the hormone which is released into the blood when its sugar level rises. Name the organ which produces this hormone and its effect on blood sugar level. Also,mention the digestive enzymes secreted by this organ with one function of each.
$(b)$ Explain the need for chemical communication in multicellular organisms.

On which type of food does salivary amylase act in the buccal cavity,and what is the name of the initial product formed due to the action of this enzyme?

$(a)$ Draw the structure of a nephron and label the following parts on it:
$(i)$ Renal artery
$(ii)$ Bowman's capsule
$(iii)$ Glomerulus
$(iv)$ Collecting duct
$(b)$ Name four substances in the initial filtrate which are selectively reabsorbed as the filtrate flows along the tubule.

Explain the three pathways of breakdown of glucose in living organisms.

Name the following with reference to the alimentary canal:
$(a)$ $(i)$ The largest gland.
$(ii)$ The gland that secretes digestive enzymes as well as hormones.
$(iii)$ The part where digested food is absorbed.
$(b)$ What are villi? Mention their function.