What separates species if not their physical appearance?
We separate species based on their reproductive compatibility. According to the biological definition of species, two organisms belong to the same species if they can interbreed to produce viable, fertile offspring.
To explore this concept a little further, let’s take the mule as an example — the offspring of a female horse and a male donkey. In this case, two different species generated a viable offspring. So why we still consider horses and donkeys different species?
Mules result from the mating of two species, but they cannot produce offspring of their own. Photo credit: George Potter on Unsplash
The answer to that question is that the mule is infertile — it can’t generate its own offspring. Therefore, it didn’t meet all of the requirements for a successful reproduction: healthy, viable, and fertile.
“Because members of a species can interbreed, the species as a whole has a common gene pool, a collection of gene variants. On the other hand, genes are not exchanged between different species. Even if organisms of different species combine their DNA to make offspring, the offspring will be sterile, unable to pass on their genes,” the Khan Academy explains.
Speciation also has an important role in the evolutionary process. Different species have their own gene collection or gene pool.
This prevents the exchange of genes and maintains species separated from each other during evolution. This process explains why we have a great variety of living organisms, each one playing its role in the ecosystem. If it weren’t for speciation, we would still be unicellular organisms swimming in the ocean.