Evolution and Natural Selection Part 1

Write what you think the definition of evolution is…

The scientific theory of evolution explains how living things descended from earlier organisms.

How do we know that organisms change over time How do we know that organisms change over time? Fossils, similarities in DNA and protein structures, similar body structures and patterns of early development all provide evidence that organisms have changed over time.

The fossil record provides clues about how and when a new species evolved and how organisms are related.

Similarities in DNA and protein structure: The more similar the DNA sequences, the more closely related the species are.

Similarities in Body Structure: Similar structures that related species have inherited from a common ancestor are known as homologous structures.

Fishes, amphibians, reptiles, birds and mammals all have an internal skeleton with a backbone. This similarity provides evidence that these animal groups all evolved from a common ancestor.

Similarities in Early Development: Scientists also infer evolutionary relationships by comparing the early development of different organisms.