Biology · The Living World · NEET
Ernst Mayr gave the biological species concept. He was a famous biologist, and NCERT calls his definition the currently accepted definition of a biological species. NEET asks this as a direct name-match question, so remember: Ernst Mayr = biological species. Do not mix him up with Carolus Linnaeus (who gave binomial nomenclature) or R.H. Whittaker (who gave the Five Kingdom classification).
It says a species is a group of organisms that can naturally breed among themselves and produce fertile offspring. "Fertile" is the key word — the young must also be able to have their own babies. So members of one species can mate and keep the group going, while members of different species usually cannot.
Because two different species can sometimes mate and make a living hybrid, but that hybrid is usually sterile (cannot reproduce). Example: a horse and a donkey mate to make a mule, but the mule is sterile. So horse and donkey are still counted as two separate species. Fertile offspring is the real test of being one biological species.
The taxonomic (Linnaean) definition groups organisms by shared visible characters — how they look. The biological species concept goes deeper: it asks whether they can interbreed and produce fertile young. So one is based on appearance, the other is based on reproduction. NEET can test both, so keep them separate.
They usually cannot, and that is exactly what makes them different species. If two groups can freely interbreed and give fertile offspring, they belong to the same species. If they are kept apart by reproductive barriers (they cannot mate, or the young are sterile), they are different species.
Study the four statements (A–D) and select the two correct ones. A. Definition of biological species was given by Ernst Mayr. B. Photoperiod does not affect reproduction in plants. C. Binomial nomenclature system was given by R.H. Whittaker. D. In unicellular organisms, reproduction is synonymous with growth.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Yes. NCERT Chapter 1 (The Living World) notes that Ernst Mayr gave the currently accepted biological definition of species, and NEET 2016 tested it directly. It is a high-yield one-mark fact.
A lion and a lioness can mate and produce cubs that can also reproduce, so all lions are one species. But a horse and a donkey give a sterile mule, so they stay two species.
Not well. It is based on sexual interbreeding, so it does not fit organisms that mainly reproduce asexually, like many bacteria. For NEET, just remember the definition and Mayr's name; the exceptions are advanced detail.
Mayr's concept defines a species by ability to interbreed and give fertile young (reproduction-based). The taxonomic species is defined by shared observable characters (appearance-based). Both terms describe the lowest taxonomic category.
