Rigid skeletons are formed from materials including chitin (in arthropods), calcium compounds such as calcium carbonate (in stony corals and mollusks) and silicate (for diatoms and radiolarians).
Answer:
Peripheral proteins have a carbohydrate extending into the environment.
Explanation:
I think that's the answer but it may not be, if not I have no idea what it is.
Answer:
Demography is the statistical study of human populations. Demography examines the size, structure, and movements of populations over space and time. It uses methods from history, economics, anthropology, sociology, and other fields.