Question

True species are A) interbreeding B) sharing the same niche C) feeding on same food D) reproductivly isolated?

Answer 1

I think that both A and D together make up the best answer, however, the answer given by the instructor is D.

Explanation:

True species are reproductively isolated, meaning they only interbreed with each other and produce viable offspring. This can be due to geographic isolation, or it can be due to certain appearances or behaviors that enable the members of a species to recognize each other.

Answer 2

Answer is D.
We may say 'members' of a species can interbreed, but this word is not mentioned in the question. That leads us to our answer, i.e. species are reproductively isolated.

Explanation:

Species is unit of classification and only naturally defined category. Several definitions of the term species are available.

• Species is a group of living organisms which randomly interbreed among themselves to produce viable offspring but do not do so with members of other species. (Members of a species may differ in morphology.)
• Species are naturally defined reproductively isolated populations. (Member of one species will never interbreed with member of another species in natural environment.)

(No two species can share the exact same niche, i.e. members of different species can not share same resources in nature for a long time. This is Gause's competitive exclusion principle.)

Both first and second definitions fall short when organisms are asexually reproducing. Hence there is an attempt to define species as a genetic unit: Earnst Mayr, who gave us biological species concept later proposed genetic species concept--

• Species is a naturally protected genepool. Member of a species is just a vehicle carrying genes from earlier generation to the next.

(This definition was still inefficient to accommodate extinct organisms and their species. )

Palaeontologist George Gaylord Simpson came up with an acceptable evolutionary species concept.

• A species is a lineage (ancestral descendant sequence of populations) that evolves separately from other such lineages and it has its own past affinities and future evolutionary tendencies.