Evolution A How Does Evolution Happen 1 Variation

Evolution

A. How Does Evolution Happen? • 1. Variation – All individuals of a species are different

• How does variation arise? – A. Meiosis • The “crossing over” event shuffles genes

• How does variation arise? – B. Mutation • Mutations can create new versions of genes (alleles)

A. How Does Evolution Happen? • 2. Overpopulation – All species produce more offspring than the environment can support

A. How Does Evolution Happen? • 3. Competition – Individuals compete for resources that are limited

A. How Does Evolution Happen? • 4. Unequal Reproduction – Some individuals reproduce more than others • Usually the better adapted

How can this moth help explain natural selection?

B. Darwin’s Finches • 1. Charles Darwin – A biologist who first described evolution – Noticed similarities/differences of birds on the Galapagos Islands

• Natural Selection – Individuals with the best traits reproduce more often

B. Darwin’s Finches • 2. Darwin’s Finches – One species of finches migrated to the Galapagos Islands – Each population evolved into different species because each island offered different food choices

Evidence for Evolution

Evidence for Evolution • 1. Homologous Structures – Traits that evolved from a common ancestor

2. Embryos • Embryos of many animals look similar early in their development – Implies a common ancestor

3. The Fossil Record • Older Fossils are found lower in the rock layers and show evidence of change