Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

How is a population defined in ecological terms?

1. A mixture of multiple species in a location

2. All the organisms in an ecosystem

3. A group of organisms of one species in a specific area

4. Organisms that do not interact with each other

The correct answer is: A group of organisms of one species in a specific area

In ecological terms, a population is defined as a group of organisms of the same species that live in a specific area at a given time. This definition highlights the focus on a single species, which allows for the study of various dynamics such as reproduction, mortality, and interactions within that particular group. Understanding populations is crucial in ecology as it forms the basis for studying species interactions, population growth, and the impacts of environmental changes. The other definitions do not accurately capture the essence of a population. A mixture of multiple species in a location refers to a community, while all the organisms in an ecosystem encompass multiple species as well as their interactions with the environment, which broadens the scope beyond a single species. Lastly, organisms that do not interact with each other would not represent a population as it is the interactions within a defined group that fundamentally contribute to the study of populations in ecology.