The answer is that they do not live on or in the body of a host.
Annelids have neither an external or an internal shell. Examples of annelids are
earthworms and leeches.
A gateway substance is something that may be menial but could lead to something bigger, an example is weed in the drugs world, weed is not hard to get and is usually a gateway drug to stronger types of drugs and potentially more dangerous
Cells divide for many reasons. For example, when you skin your knee, cells divide to replace old, dead, or damaged cells. Cells also divide so living things can grow. When organisms grow, it isn't because cells are getting larger.
Answer:
look below
Explanation:
1) keep toxic substances out of the cell
2) allows certain minerals in that are needed and keeps others out and uses reciptors to do so
3) they separate vital but incompatible metabolic processes conducted within organelles
