Evidence for Evolution Topic 5.1

Evolution Occurs when heritable characteristics of a species change over time *Characteristics acquired over a lifetime (such as blisters) are not heritable Occurs through natural selection

Evidence: Selective Breeding Humans have been breeding plants and animals purposefully for thousands of years through artificial selection The breeds of these animals greatly vary from their wild counterparts Shows that selection can cause evolution

Evidence: Fossil Record The sequence of the fossil record matches evolutionary theory. Older, simpler fossils are found in the bottom strata of rock layers Newer, more complex fossils are found in the upper strata of rock layers

Evidence: Fossil Record Sequence of the fossil record matches theory: Plant fossils appear on land before animal (herbivores) fossils do Some sequences of fossils are known Link together common ancestors Predicts close living relatives accurately

Evidence: Homologous Structures Homologous structures are structures in different species that may look different, perform different functions but have a common structure and common origin. Ex: forelimbs in humans, cats, whales and bats

Pentadactly limb: Forelimb

Homologous structures are not to be confused with analogous structures Analogous structures have similar functions and may have similar shapes, but do not have a common origin. They have evolved independently of each other

Evidence: Patterns of Variation If populations gradually diverge over time, we should be able to see examples of populations in different stages of divergence Variation within a species that is recognizable, but not enough to be considered a different species.

Peppered moth populations in pre and post industrial England Peppered moths (Biston betularia) have natural variation in their wing colors Melanic: dark colored wings (morpha: typica) Non-melanic: light colored wings (morpha: carbonaria) Peppered moth populations in pre and post industrial England

Explain the trends seen in the graph above

Evidence: Speciation Populations of a species can gradually diverge into separate species by evolution Speciation occurs when a population becomes separated into two or more groups and are cut off from breeding with each other. Over time each group will evolve in different ways, creating distinct characteristics. If the two different populations can no longer successfully breed with each other, they have speciated into two distinct species.

*Speciation occurs often on islands where species are geographically isolated. These populations are endemic: only found in a distinct geographic areas.

Evidence: Speciation Geographical distribution of species matches the idea of gradual speciation *Different species of mockingbirds are distributed in the galapagos islands suggesting the main island was populated first and outlying islands populated from the main island species then speciated.