Question

The species diversity of an evolutionary lineage will increase when more new member species originate than are lost to extinction. In this hypothetical example, by 2 million years ago, both lineage A and lineage B have given rise to four species, and no species have become extinct (denoted by a dagger symbol). By time 0, however, lineage A contains only one species while lineage B contains eight species. Part A Consider the period from 2 million years ago to time 0. For lineage A, how many speciation and extinction events occurred from 2 million years ago to time?

Answer 1

Answer:

A. 2 speciation events and 5 extinctions

B. 5 speciation events and 1 extinction

Explanation:

As we can see from the diagram, there were only 2 ,aim speciation events for lineage A. The extinction events were 5 for the A lineage. Hence, as the extinction event was more rapid than the speciation event so lineage A contains only one species.

On the other hand, the diagram shows that for lineage B there were 5 speciation events and just 1 extinction event. Hence, the number of species in lineage B were more at the time zero as just one extinction had occurred.