Biological Species Concept
The most widely accepted definition of a species is the biological species concept. This states that a species is a group of organisms that can interbreed and produce fertile offspring in nature.
Applying the Concept to Horses and Donkeys:
1. Interbreeding: Horses and donkeys can indeed interbreed. This results in a hybrid offspring called a mule or hinny (depending on the parent sex).
2. Fertility: The key issue is that mules and hinnies are almost always infertile. They cannot reproduce with each other or with either parent species (horses or donkeys).
Conclusion
Because the offspring of horses and donkeys (mules and hinnies) are infertile, the biological species concept dictates that horses and donkeys are considered separate species.
Important Note: While the biological species concept is widely used, it's not perfect. There are other ways to define species, and in some cases, the biological species concept can be difficult to apply.
Further Considerations:
* Genetic evidence: DNA analysis has confirmed significant genetic differences between horses and donkeys.
* Evolutionary history: Horses and donkeys diverged from a common ancestor millions of years ago, which further supports their distinct species status.