Common ancestors and transitional species | Exit Quiz | Oak National Academy

What does the diagram show?

• a classification key

• a family tree

• a food web

• an evolutionary tree

Answer explanation

An evolutionary tree diagram shows how later species have evolved from earlier ones. (A family tree shows how individuals of the same species are related, a classification key includes yes/no questions, a food web shows feeding relationships.)

Which species, A, B or C, would be called a common ancestor?

Answer explanation

“Common ancestor” is the scientific term used for a species that evolved into several other species. The evolutionary tree shows that species A evolved into species B and C.

Match each species (A, B and C) to the correct description.

• B

• the most recent common ancestor of gorillas and humans

• C

• a common ancestor of orangutans and humans

• A

• a common ancestor of chimpanzees and humans but not of gorillas

Answer explanation

Chimpanzees and humans both evolved from species C, so it is their common ancestor. But gorillas evolved from species B; their common ancestor is chimpanzees and humans. The only common ancestor of orangutans and humans is species A.

Why is *Archaeopteryx* said to be a transitional species between dinosaurs and modern birds?

• It does not have any features of dinosaurs or modern birds.

• It has features of dinosaurs and modern birds.

• It only has features of dinosaurs.

• It only has features of modern birds.

Answer explanation

A transitional species such as *Archaeopteryx* has characteristics of its evolutionary ancestors and characteristics of the modern species it evolved into.

Who correctly explains why *Ambulocetus* is considered to be a transitional species between *Indohyus* and the modern baleen whale?

• Alex: “Ambulocetus has back legs like Indohyus.”

• Laura: “Ambulocetus has a broad front foot like the whale’s flipper.”

• Lucas: “I think it’s because of both of those things.”

Answer explanation

A transitional species such as *Ambulocetus* has characteristics of its evolutionary ancestors and characteristics of the modern species it evolved into.

True or false? This evolutionary tree diagram suggests that all life on Earth evolved from a common ancestor.

• true

• false

Answer explanation

A common ancestor is a species that several other species evolved from. The evolutionary tree diagram shows that all species on Earth evolved from a very early common ancestor (probably a unicellular organism, the very first living thing on Earth).