Evidence for Evolution
- Biology
- Ages 11–14 · Grades 6–8
What you’ll find out
- The fossil record shows life changing over time, from simple to more complex, with transitional forms.
- Homologous and vestigial structures and similar embryos point to common ancestors.
- DNA comparisons independently confirm the relationships shown by fossils and anatomy.
No sign-up and no real names. In the lesson you check your understanding as you read, and practise until it sticks.
The fossil record
The fossil record, the collection of all fossils found so far, shows that life on Earth has changed enormously over time. Older, deeper rock layers contain simpler organisms, while younger layers contain more complex ones. Some fossil sequences show gradual change: the earliest ancestors of horses were dog-sized animals with several toes on each foot, and over some fifty million years their descendants became larger, with longer legs and a single hoof. The record also shows that most species that ever lived are now extinct.
Clues in living things
Living organisms provide further evidence. A human arm, a cat’s leg, a whale’s flipper and a bat’s wing are used for very different jobs, yet they contain the same set of bones arranged in the same pattern. Such similar structures suggest that these animals share a common ancestor. The early embryos of fish, birds and mammals also look surprisingly alike. Today, comparing DNA confirms these relationships: the more similar two species’ DNA, the more recently they shared an ancestor.
Curriculum links: NGSS MS-LS4-1 · NGSS MS-LS4-2 · England KS3: Genetics and evolution · Cambridge Lower Secondary Stages 7–9: Biology · NCERT Science, Classes 6–8