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

• a common ancestor of orangutans and humans

• C

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

• A

• the most recent common ancestor of gorillas and humans

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).