Is so much but I’m answering in my house and i help you ok one is A
The hormone described above is the hormone Melatonin.
Melatonin is a hormone secreted by the pineal gland in the brain, which helps regulate other hormones and maintains the body's circadian rhythm. This rhythm is an internal 24 hour clock that plays a critical role when we fall asleep and when awake. When it is dark the body releases more melatonin.
The food sources available for a particular species in an ecosystem. Also space where they can live and reproduce, but food is the main factor.