Which of the following describes a biotic factor in an ecosystem?

A biotic factor in an ecosystem refers to any living component that influences or interacts with other organisms within that ecosystem. This includes all forms of life, such as plants, animals, fungi, and microorganisms. By understanding that these living elements play crucial roles in various ecological processes—like competition for resources, predation, and symbiosis—it's clear why the definition of a biotic factor is inherently tied to these living organisms.

In contrast, the other options presented pertain to abiotic factors, which include non-living components of an ecosystem that can also have significant effects on the living organisms. For instance, temperature changes, geological formations, and weather patterns, while highly influential in shaping the environment and habitat, do not include living beings and thus do not fit the description of biotic factors. Therefore, the choice highlighting living components encapsulates the essence of what biotic factors represent in any given ecosystem.