I chose the answer that said "Transition to socialist and communist government systems, and creation of labor unions."
Answer: You picked the correct answer, "They all inherited their traits from a common ancestor."
Explanation: Well, one I had a test on this question too and I got it right. Second, if all species shown have something in common (structures) than they most likely got it from a common ancestor.
They are called paleontologists.
The species was a keystone species.
Keystone species are the species that ''hold the ecosystem together''.
They have an important role in the trophic networks (food chains) and often they can even afflict changes in the abiotic part of the ecosystem (change the composition of soil, purify the water, lower the effect of the wind etc)
Therefore, when a keystone species is removed it affects greatly the whole ecosystem.
