Question

Which of the following is one of the reasons why prokaryotes are not considered in the estimates of global species diversity?

• A. Prokaryotes are not considered as living organisms
• B. Biologists believe that prokaryotes do not show any species diversity
• C. It is difficult to study prokaryotic species diversity using conventional taxonomic methods
• D. Biologists believe that the species diversity shown by prokaryotes is much less and hence can be ignored

Answer 1

The correct option is C It is difficult to study prokaryotic species diversity using conventional taxonomic methods

Prokaryotes are living organisms that lack a well-defined membrane bound nucleus and cell organelles. They are microscopic and have been known to exist everywhere, right from the place with extreme temperatures to ocean beds and even in the body of other organisms. Thus, indicating to a vast species diversity.

Hence statements a, b and d are incorrect.

According to the IUCN (2004), the total number of described species of plants and animals on earth is more than 1.5 million and a scientifically sound estimate given by Robert May states that the total number of species (plants and animals) in the world is around 7 million.

But these numbers do not include the number of prokaryotic species. This is because -

• Identification and classification of prokaryotic species is not possible by conventional methods which generally involves the comparison of the physical characteristics of a collected specimen with the characteristics of a known species.
• Many prokaryotic organisms are impossible to culture in vitro and hence cannot be studied properly.

Hence option c is the correct reason.