Final answer:
A population refers to a group of organisms of the same species that live in the same area and interact with each other, which is described by option a) The members of a species in a given area. Studied by ecologists, these populations can be analyzed in various aspects such as density and reproductive rates.
Step-by-step explanation:
The definition that best describes a population is: a group of organisms of the same species, all living in the same area and interacting with each other. Populations are crucial units for ecologists to study because they can determine how healthy or stable the populations are, understand the interactions among individuals within a population, and examine how populations interact with their environment. For example, when considering the angelfish population in a section of the ocean, we are referring to all the angelfish that are interacting and reproducing in that particular area.
Ecologists study many aspects of a population, including its density, dispersion, and birth and death rates. Populations are comprised of conspecifics—organisms that are all members of the same species—and are identified by where they live, which may have natural or artificial boundaries. A species, to clarify, is defined as a group of individuals that are genetically related and capable of breeding to produce fertile offspring.