From which one of the following,the melatonin is derived?

Select the correct match regarding the source and function of the hormone.

Artificial light, extended work-time and reduced sleep-time disrupt the activity of

Melatonin is secreted by ..........

$I.$ Sleep-wake cycle,$II.$ Body temperature,$III.$ Pigmentation,$IV.$ Metabolism,$V.$ Defence capability. All of the above-mentioned activities are influenced/regulated by:

The organ which was considered vestigial until recently but is now confirmed to be an endocrine gland is: