The biome in which an organism resides affects just about everything. In general, the biome is everything that surrounds an organism, including other organisms. Population ecology is generally the study of how animal populations change over time. So, the way the biome interacts with a population would be how population ecology is affected. For example, there's a big problem with fungal infections in amphibians, where this fungus lives in ponds, infects frog skin, and causes the frogs to die. So, when that fungus enters a pond, it becomes part of the frog's biome. That fungus can then infect the frogs and change their population. This is just a simple example, but any changes in the biome will ultimately affect the population in some way.