Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The estimates of the number of species of major taxa on earth do not give any figures for prokaryotes.
Reason (R): Conventional taxonomic methods are not suitable for identifying microbial species, and many species are simply not culturable under laboratory conditions.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both (A) and (R) are true and (R) is the correct explanation of (A).
Assertion (A): The estimates of the number of species of major taxa on earth do not give any figures for prokaryotes. — True. A is about what the global species estimates leave out. The book says these estimates give no figures for prokaryotes; biologists are not sure how many prokaryotic species there are.
Reason (R): Conventional taxonomic methods are not suitable for identifying microbial species, and many species are simply not culturable under laboratory conditions. — True. R is about the difficulty of studying microbes. Usual classification methods do not work for them, and many cannot be grown in the laboratory.
Why R explains A? A species can be counted only if it can be identified. If microbial species cannot be identified by usual methods and cannot even be grown, there is no reliable way to count them, so the estimates leave prokaryotes out. The book itself calls this “the problem” behind the missing figures. So R is the correct explanation of A.
NCERT Extract:
How Many Species are there on Earth and How Many in India? – “… It should be noted that these estimates do not give any figures for prokaryotes. Biologists are not sure about how many prokaryotic species there might be. The problem is that conventional taxonomic methods are not suitable for identifying microbial species and many species are simply not culturable under laboratory conditions. If we accept biochemical or molecular criteria for delineating species for this group, then their diversity alone might run into millions.”