Is the brain an organ or an organ system?

In a certain ecosystem owls are predators for mice. the owl population increases and they eat more mice this causes the mouse population to decrease what happens next? a.the birth of mice increases. b. the birth rate of owls increases c. the population of owls decreases d. the population of mice increases

Which mechanism of transport takes place when solute particles move from a region of high concentration to a region of low concentration? active diffusion isotonic osmosis

Where does the esophagus lead to in a frog?