This question is for sci-fi writing novel. The premise is that this planet is generally habitable, and a human colony has been established.

The point is that, at the equator, day lasts on average 8 hours, going down to almost 4 (or less) during winter and up to 12 (or more) during summer. Night follows suit accordingly, with the total day/night cycle to complete in about 16 hours.

1. What will the effects be on the climate and geography?
2. On biology (local and imported from Earth)?
3. Specifically on humans?
4. Is there anything specific about its orbit and/or moons that I should pay attention to?
5. Any other point in world-building I should be aware?

Thank you very much. This is my very first question in worldbuilding, so feel free to assist me in the proper way of asking, as well.