Answer: Serotonin
Explanation:
Serotonin is an hormone, derived from the amino acid, tryptothan. It is involved in vasodilation, sleep regulation, mood changes, capillary permeability, and causes contraction of smooth muscles like that of the stomach to signal hunger.
Water or other molecules move down their concentration gradient without any energy.........
difference - simple diffusion uses help of transporting protein in the membrane whereas osmosis uses no help.
a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membran.
An herbivore would belong to the second trophic level in an ecosystem. An herbivore is an animal that eats only plants, making it a consumer at the second level. The first trophic level is always made up of producers, or organisms that undergo photosynthesis such as plants.