Question

Nicotiana sylvestris flowers only during long days and 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?
A. They are physiologically distinct.
B. They are morphologically distinct.
C. They cannot interbreed in nature.
D. They are reproductively distinct.

Answer 1

Hint:
Before we proceed into the problem, it is important to know the definition of species.
Flowering occurs at distinct photoperiods in N. Sylvestris and N. tobacum. The term species can alternatively be defined as the most fundamental category in the taxonomy system. Taxonomy is a scientific technique for categorizing organisms based on biological properties. Species can also be characterized by their common evolutionary history and ancestors.

Complete step by step answer:
Both Nicotiana sylvestris and Nicotiana tobacum can be intentionally cross-pollinated to produce fertile offspring, but they are unable to interbreed freely in nature. As a result, they belong to separate species.
They also have different physiological traits that distinguish them from one another as a species. They share the same reproductive process, yet pollen from one species frequently fails to develop and fertilize pollen from another.
Therefore, the best reason for considering N. sylvestris and N. tobacum to be separate species is they cannot interbreed in nature.

Option ‘C’ is correct

Note:
Nicotiana sylvestris blooms exclusively on long days, whereas Nicotiana tobacum blooms only on short days. They can be coaxed to flower at the same time and cross-pollinated to create self-fertile offspring if cultivated in the laboratories under distinct photoperiods.