Which term defines a group of organisms of the same species living in the same habitat at the same time?

The term that defines a group of organisms of the same species living in the same habitat at the same time is "population." A population is a fundamental concept in ecology, emphasizing the importance of studying groups of the same species as they interact within their environment. This allows for the examination of how these organisms reproduce, compete for resources, and adapt to their surroundings.

In contrast, other terms such as "polysome" refer to a complex of ribosomes actively translating an mRNA molecule, which is unrelated to organisms or their habitats. "Polyspermy" describes a condition in sexual reproduction where more than one sperm fertilizes an egg, which is not relevant to the definition of a group of organisms. "Positive feedback" refers to a process in which an initial change leads to further changes in the same direction, often seen in biological systems like hormone regulation, but does not pertain to the definition of a group of organisms based on species and habitat.