Species - LeFonch

What is a Species?

A species is a distinct group of organisms that have more similarities with members within the species than with other species.
Two organisms in the same species can interbreed, producing viable and fertile offspring.
All members of a species have a constant genomic structure and number of chromosomes.
Different species have different numbers of chromosomes, preventing breeding viable offspring.
For example Horses have a diploid of 64 chromosomes and donkeys 62 chromosomes. Their hybrid, mules, have 63 diploid chromosomes. This means that even haploid chromosomes cannot be formed in order for reproduction.
Two organisms can look very different but look alike for the most part. This does not resolve if they belong to the same species.
For example the African fish eagle and the bald eagle are both very similar, but are separate species as they cannot interbreed.
On the opposite spectrum, dog breeds look very different but they can all interbreed and are part of the same species.

A species is the smallest group in taxonomy, underneath a genus.
When writing about species, the genus name is mentioned first, and then the species name.
For example Apatosaurus ajax, or A. ajax.
However it can further be separated into sub-species. Sub-species can generally be defined as closely related enough to breed but very different morphologically.
For example dogs and wolves look very different but can still breed. Thus dogs are generally considered a sub-species of wolves, called Canis lupus familiaris.

An endemic species means that the species is restricted to only a certain area.
Endemic species are usually endangered as they are prone to man-made threats.
In geographically isolated areas, unique species may evolve.
Most common examples are species that develop in remote lakes or islands.
A very well known example are Darwin's finches. The finches all evolved from a common ancestor that came upon an isolated island in the Galapagos. Over time the finches had all adapted to different diets due to competition over food and became distinct species.