All the individuals of a species that live in a particular area are called a. variation. b. fossil. c. population. d. vestigial structure __ : A relationship in which one organism benefits and the other is unharmed a. commensalism b. analogous structure. c. homologous structure. d. fossil structure.

The answer to the first question is **c. population**. A population is defined as all the individuals of a single species living in a specific geographical area and capable of interbreeding.<br /><br />The answer to the second question is **a. commensalism**. Commensalism is a symbiotic relationship where one organism benefits and the other is neither harmed nor helped.<br />