Answer:
Reproductive isolation is the very factor that causes the development of what we call "species" according to the biological species concept. The reason cats and dogs are different species is that they can't mate, so we call them "reproductively isolated."
Answer:
A nickel is a five-cent coin struck by the United States Mint. Composed of 75% copper and 25% nickel
Taking in oxygen is very important because it allows your cells to do things, like make energy from the food you eat. Plants 'breathe' too, but they do it through tiny openings in leaves called stomata. Stomata open and close to allow the intake of carbon dioxide and the release of oxygen.