Biology · The Living World · NEET
Robert May estimated the total global species diversity to be about 7 million. This is his estimate of how many species probably exist in total, including the ones we have not found yet. In NEET, if the question asks 'According to Robert May', the answer is 7 million.
Both numbers are correct, but they mean different things. 1.7 to 1.8 million is the number of species already KNOWN and DESCRIBED (found, named, recorded). 7 million is Robert May's ESTIMATE of the TOTAL number that actually exist on Earth. Read the question carefully: if it says 'known/described', pick 1.7–1.8 million; if it says 'according to Robert May' or 'global species diversity', pick 7 million.
Because a huge number of species have not been discovered yet. Many live in places that are hard to explore, like deep oceans, dense tropical rainforests, and soil. Many are tiny (insects, microbes). New species are still being found every year. So the exact number is unknown, and scientists can only estimate it. This is why NEET uses the word 'estimate' for the 7 million figure.
A 'described' species means a species that scientists have officially found, studied, and given a proper name to, with a written record. Only about 1.7–1.8 million species have been described this way. The rest of the estimated 7 million are still undiscovered or unnamed.
Not exactly. Biodiversity means the number and variety of all living organisms. The KNOWN biodiversity is the 1.7–1.8 million described species. Robert May's 7 million is an estimate of the TRUE total biodiversity, most of which is still unknown to us.
According to Robert May, the global species diversity is about:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
NCERT states that the number of species known and described ranges between 1.7 and 1.8 million. This refers to biodiversity, the number and variety of organisms present on Earth.
Robert May was a scientist who studied biodiversity. He estimated that the total number of species on Earth is about 7 million, far more than the number we have described so far.
Because most species on Earth have not yet been discovered, especially in oceans, rainforests, and soil. Since we cannot count what we have not found, the total can only be estimated, not counted exactly.
Remember both: 1.7–1.8 million = known and described species; about 7 million = Robert May's estimate of total species. NEET has asked both, so match the number to the wording of the question.
