Abiotic factors are non-living factors in an environment.
There is not much light available in a shady forest so plants are in competition for light.
In order to reproduce sexually, organisms compete with each other to find a mate.
If available resources in any environment decrease, the level of competition between organisms increases as they compete with each other for the few resources that are available.
Extremophiles are organisms adapted to living in extreme environmental conditions. Those that live in brine pools are adapted to living in regions of high salt concentrations.