High tides and low tides are caused by the Moon. The Moon's gravitational pull generates something called the tidal force. The tidal force causes Earth and its water to bulge out on the side closest to the Moon and the side farthest from the Moon. These bulges of water are high tides.
A covalent bond is also called a molecular bond. it’s the chemical bond that involved the sharing of electron pairs between the atoms.
A community will be affected by the extinction or migration of a single species because all species in a community interact and are interconnected. The community can be affected in a number of ways including changing population sizes and disrupting symbiotic relationships.
I say it's in both because every cell has a Nucleus.