Connect melanin and melatonin and talk about the systemic effect
between them?

Melatonin is released by the pineal gland, that is hormones or neurotransmitter which is related to the sleep. It is influence the sleep wake  cycle. Where as melanin is pigment that naturally colors skin or the hair. More the melanin more the darker the skin or hair.

Melatonin regulates changing in pigmentation by association of melanin into the melanocytes within the skin, leads to the skin to color change. This relation is is also accountable for the yellowish skin color in elderly people and people with insomnia.

answer:

i don't know

explanation:

sorry

answer:

it could come from a variety of sources.

explanation:

..although it was most likely developed through zoonotic transmission, where an infectious disease which usually afflicts when animals jump to humans.