Question

Nicotiana sylvestris requires long days for flowering while Nicotiana tobacum requires short days for flowering. When both these were grown in a laboratory under controlled conditions of different photoperiods, they could be induced to
flower at the same time and also could be artificially cross pollinated to produce fertile offspring.

Which would be the best reason to classify N. sylvestris and N. tobacum under separate species?

• A. They are morphologically and physiologically different from
  each other.
• B. They cannot interbreed in nature.
• C. They are reproductively different.
• D. They produce different secondary metabolites.

Answer 1

The correct option is B They cannot interbreed in nature.

A "species" is a group of organisms that are capable of breeding within the group naturally to produce fertile offsprings.

Both Nicotiana sylvestris and Nicotianna tobacum could be made to cross pollinate artificially to produce fertile offsprings but they are incapable of interbreeding freely in nature. Hence they belong to different species.

They also exhibit different physiological characteristics which differentiates them form one another as a species. They use the same reproductive mechanism but majorly, pollen of one species fail to grow and fertilise another species naturally.