Final answer:
Fine-grained environmental variation refers to small-scale differences in environmental conditions within a given area that can have significant impacts on local organisms and their ecological interactions.
Step-by-step explanation:
Fine-grained environmental variation refers to small-scale differences in environmental conditions within a given area. This variation can be due to a range of factors, including differences in moisture, sunlight, soil type, and topography. Such slight variations can have significant impacts on the organisms living in these environments, affecting their growth, behavior, and evolution. For instance, flowering plants may bloom at different times based on their position along a mountain slope—an effect known as an altitudinal cline. Similarly, animal populations can show a range of phenotypic differences across an ecological gradient, as seen in the body size variation of warm-blooded animals along a latitudinal cline.