The abiotic or non living factor in an environment includes sunlight, temperature, pressure, mountain slope, soil, rainfall, land drainage and atmosphere. These physical factors interact with one another. Let us take a soil as an example. This soil can be affected by heavy rainfalls or floods. We refer to the life in an ecosystem as the biotic community. It is a naturally occurring assemblage of plants and animals which are categorized as biotic factors. These factors live in the same environment which are mutually sustaining and are interdependent.
A biotic community has three biological sublevels. The first level is known as the population. This will include humans, dogs, birds and horses from their own population. Population refers to any group of organisms of the same species. They are then defined by space and time in a particular ecosystem. For example, we may refer to the plant-eating fish population river in the summer of 2000. At the same time, a big insect population may have existed.
The second level is known as the species itself. A group of organisms that look alike and are capable of producing fertile or productive offspring in their natural environment is referred as specie. For example in a forest, there are thousands of species of plants as well as insects and other animals. A forest ecosystem will have more species of organisms than a grassland system. Last but certainly not the least is the third level which is the individual. This is the only single member in a particular population.
You can witness relationships in a particular ecosystem. There will be some relationships among biotic factors in the biotic community. There will be also relationships between the biotic community and the physical environment. Finally, there will be relationships among physical factors in the environment too. You can really say that there are a variety of interactions occurring in the ecosystem.