Letters A through F on the graph below represent different species that are related but show different structural, functional, and behavioral adaptations.
Increasing Level
of Complexity
more
Time (millions of years)
One inference that can be drawn from the graph is that
A) speciation may be either gradual or abrupt.
B) speciation occurs only gradually, over long periods of time.
C) species E is the ancestor of species F.
D) species E resulted from the extinction of species A, B, C, and D.

A) speciation may be either gradual or abrupt.

whats the answer to your question?

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.