All the fossils ever found, and their ages, provide a body of evidence called the fossil record.

A species that several other species evolved from. For example, tigers and lions share a common ancestor.

A diagram that shows the evolutionary relationships between different groups of organisms.

A species that shows intermediate characteristics from evolutionary ancestors and modern species.

Common ancestors and transitional species

Biology

Pupils will learn about random genetic mutation as a source of heritable variation, and that evolution occurs through the natural selection of genetic variants linked to advantageous phenotypes that are best suited to the environment.

Pupils learned that (phenotypic) variation between individuals of the same species means some individuals are better adapted to compete, which can lead to natural selection and cause the heritable characteristics of a species to change (evolve) over generations.

Fossil evidence, selective breeding and explaining evolution

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

a common ancestor of orangutans and humans

the most recent common ancestor of gorillas and humans

a common ancestor of chimpanzees and humans but not of gorillas

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

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

It has features of dinosaurs and modern birds.

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

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.”

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

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

organisms from which current, living organisms are descended

changes in the characteristics of a species over many generations

changes in an individual organism during its lifetime

differences between living individuals of the same species

Match each term to the correct definition.

All the fossils ever found and their ages.

The habitat where a fossil is discovered.

The mineralised remains of a single dead organism.

These fossils are part of the fossil record. They are all evolutionary ancestors of the modern whale. Starting with the earliest ancestor, sort them into order. End with the most recent ancestor.

A fossil proves that all members of the species looked exactly the same.

Fossils show us exactly what the living organisms looked like.

From a fossil we get evidence of an organism’s size, shape and body structures.

Most fossils are complete and intact when they are found.

Scientists must use their judgement/ imagination to interpret fossil evidence.

Andeep: “There are many fossils out there which we haven’t yet found.”

Jun: “We have only found fossils from the past 10 thousand years.”

Sam: “It’s rare for organisms to become fossils. Conditions aren’t often right.”

Sofia: “Plants, fungi and bacteria can’t be turned into fossils.”

Who explains why there are gaps in the fossil record?

It shows how many species there have ever been.

It shows how the features of species have changed over time.

It shows similarities and differences between organisms now and from the past.

It shows that some species are now extinct.

How does the fossil record provide evidence for evolution?

This lesson will be removed by end of Summer Term 2025.

Common ancestors and transitional species

Lesson outcome

This lesson will be removed by end of Summer Term 2025.