An ecosystem has multiple entities which are influenced by each other in a way or more, not only by biotic components but by abiotic components as well. A species is a unique kind of an entity where different individuals are capable of reproducing their offsprings. Interspecies reproduction does not take place or produces sterile offspring.
Species are made up of populations which is dependant on the geographical area. Some species are spread across a limited area, for instance – island, mountain top etc. The single population in such regions constitute for the entire species. This population is extremely endangered and hence are at high risk of becoming extinct. Some other species are spread across places.
Species refers to an individual entity which produces its own offspring, for instance, horses can produce their offspring but, a zebra and horse would produce a Zorse, a donkey and a horse would produce a mule which is not fertile and hence mules are not called species since they are incapable of reproducing. Hence we conclude that horses and donkeys are two different species.
A population, on the other hand, are a category of individuals belonging to the same species, living in a particular region which contains genetic variation within themselves. In the case of migration, it can be across multiple ecosystems. If a population is isolated for longer durations from other populations, they may become genetically different and hence become their own species.
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