Under the biological species concept, what criterion is used to assign populations of organisms to the same biological species?
a. a very similar appearance
b. being able to interbreed and produce fertile offspring
c. relating to the environment in the same way
d. having 99% of their genes in common
The correct answer and explanation is :
The correct answer is:
b. being able to interbreed and produce fertile offspring
Explanation:
The biological species concept (BSC), primarily developed by evolutionary biologist Ernst Mayr in the 20th century, defines species based on their ability to reproduce and produce fertile offspring. According to this concept, populations of organisms are considered to belong to the same species if they can interbreed under natural conditions and produce offspring that are fertile and capable of reproducing themselves. This criterion emphasizes reproductive isolation as the key factor in determining whether two populations belong to the same species or not.
Reproductive isolation can be due to various factors, such as geographic isolation, behavioral differences, or physical incompatibilities that prevent successful mating. If two populations can interbreed but their offspring are sterile or cannot reproduce (like the mule, a hybrid of a horse and donkey), they are considered different species under this concept.
For example, horses and donkeys are two distinct species because, while they can interbreed to produce a mule, the mule is typically sterile, meaning it cannot reproduce. This reproductive isolation is the primary reason they are classified as separate species under the biological species concept.
Why the other answers are incorrect:
- a. a very similar appearance: Similar appearance (morphological similarity) can sometimes be used to group organisms, but it is not a reliable criterion for species identification, as organisms with similar appearances may not be able to interbreed (e.g., some species of frogs that look alike but are reproductively isolated).
- c. relating to the environment in the same way: Environmental factors alone don’t determine species boundaries. Two species can occupy the same ecological niche but still be reproductively isolated.
- d. having 99% of their genes in common: While genetic similarity can indicate relatedness, it does not guarantee that two populations can interbreed successfully or produce fertile offspring. Species can have very similar DNA but still be reproductively isolated.
Thus, the biological species concept centers on the ability to reproduce and have viable offspring, making option b the correct choice.