Bellringer What is genetic drift? What are two mechanisms (ways it is caused) of genetic drift? Once done answering the bellringer question on your sheet, please add questions (2 per page) and a summary to your Darwin and Natural Selection Notes. Summary 3 things you learned 2 things you found interesting 1 question you still have

Evidence for Evolution

Learning Targets Explain three ways natural selection can change the distribution of a change in a population Explain the evidence for evolution with regards to the fossil record, geographic distribution of organisms, anatomical structures, embryology, and molecular biology. Be able to compare and contrast homologous, analogous, and vestigial structures.

Review of Natural Selection Remember Darwin came up with the Theory of Evolution. Natural selection leads to Descent with Modification – traits are passed down from generation to generation and sometimes undergo changes or modifications over time

Three ways natural selection can change the distribution of a population    Disruptive

This is __________ Selection: Favors phenotypes at one extreme of a trait’s range. 1. Directional

This is __________ Selection: Intermediate phenotype favored and becomes more common in population 2. Stabilizing

This is __________ Selection: Occurs when BOTH extreme phenotypes are favored, intermediate phenotypes selected against. 3. Disruptive

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Evidence for Evolution  Evidence for Evolution Fossil record Shows change over time. Fossils of extinct species provide evidence of shared ancestry and how organisms and the environment have changed over time. Biogeography Differences and similarities between organisms in different locations around the world. Provides evidence of how modern species share a common ancestor but have evolved to fit environments in different locations.

Evidence for Evolution Anatomical strucures comparing body structures, similarities and differences. Molecular record comparing protein & DNA sequences. The greater the similarities in DNA and protein sequences, the more likely two organisms share a common ancestor. Universal genetic code (ATGC) provides evidence that ALL life forms are related.

Evidence for Evolution Embryology comparison of stages of embryonic development between organisms of different species. Embryos of closely related species have similar stages of development.

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Anatomical Structures  Anatomical Structures Homologous structures-structures that come from the same origin, but have different functions. homo- = same -logous = information Forelimbs of human, cats, whales, & bats same structure on the inside same development in embryo different functions on the outside evidence of common ancestor Divergent Evolution (similar ancestor, but due to isolated environments evolve to adapt best to environment)

Anatomical Structures  Anatomical Structures Analogous structures:  structures that have a similar function but do NOT have similar internal structure. look similar on the outside same function different structure & development on the inside different origin no evolutionary relationship Convergent Evolution (similar living environments, adapted in similar way).

Convergent evolution (Analogous structures)  Convergent evolution (Analogous structures) evolving similar solutions to similar problems 3 groups with wings Does this mean they have a recent common ancestor?

Analogous or Homologous? Dolphins: aquatic mammal Fish: aquatic vertebrate both adapted to life in the sea not closely related

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Anatomical Structures Vestigial Structures: Remnants of structures that may have had important functions in an ancestral species but have no clear function in the modern species  shows common ancestry with adaptations to changing environments.

Discuss with a Partner What are the Main Evidences for Evolution? Which do you feel is the strongest support of Natural Selection? Why?