Species that are morphologically similar but reproductively isolated are called ..........

Which one of the following statements is correct about biodiversity?

Identify the incorrect statement with respect to the rules of Binomial Nomenclature.

The process of grouping organisms into convenient categories based on easily observable characters is called:

The system of providing a name with two components is called...

$Nicotiana$ $sylvestris$ flowers only during long days,while $N.$ $tobacum$ flowers only during short days. If raised in the laboratory under different photoperiods,they can be induced to flower at the same time and can be cross-fertilized to produce self-fertile offspring.
What is the best reason for considering $N.$ $sylvestris$ and $N.$ $tobacum$ to be separate species?