3. Anatomical record Animals with different structures on the surface But when you look under the skin… It tells an evolutionary story of common ancestors

Compare the bones (anatomical structures) The same bones under the skin limbs that perform different functions are built from the same bones How could these very different animals have the same bones?

Homologous structures Structures that come from the same origin 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

But don’t be fooled by these… Analogous structures look similar on the outside same function different structure & development on the inside different origin no evolutionary relationship Convergent evolution!! How is a bird like a bug? Solving a similar problem with a similar solution

Analogous structures Dolphins: aquatic mammal Fish: aquatic vertebrate both adapted to life in the sea not closely related Watch the tail!

Because they used to walk on land! Vestigial organs Hind leg bones on whale fossils Why would whales have pelvis & leg bones if they were always sea creatures? Because they used to walk on land!

Vestigial organs Structures on modern animals that have no function remains of structures that were functional in ancestors evidence of change over time some snakes & whales have pelvis bones & leg bones of walking ancestors eyes on blind cave fish human tail bone

Comparative embryology Development of embryo tells an evolutionary story similar structures during development all vertebrate embryos have a “gill pouch” at one stage of development

3. Molecular record Comparing DNA & protein structure everyone uses the same genetic code! DNA 10 20 30 40 50 60 70 80 90 100 110 120 Lamprey Frog Bird Dog Macaque Human 32 8 45 67 125 compare common genes compare common proteins number of amino acids different from human hemoglobin

Phylogeny! Building “family” trees Closely related species are branches on the tree — coming from a common ancestor

“descendants” of wild mustard 4. Artificial selection How do we know natural selection can change a population? we can recreate a similar process “evolution by human selection” “descendants” of wild mustard

“descendants” of the wolf Selective Breeding Humans create the change over time “descendants” of the wolf

I liked breeding pigeons! Artificial Selection …and the examples keep coming! I liked breeding pigeons!

Artificial Selection gone bad! Unexpected consequences of artificial selection Pesticide resistance Antibiotic resistance

Insecticide resistance Spray the field, but… insecticide didn’t kill all individuals variation resistant survivors reproduce resistance is inherited insecticide becomes less & less effective Genetic Drift! The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action. The results of application of new insecticide are typically encouraging, killing 99% of the insects. However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases. This is an example of genetic drift.

So, do individuals or populations evolve? So…what is a species? species population whose members can breed & produce viable, fertile offspring reproductively compatible Distinct species: songs & behaviors are different enough to prevent interbreeding So, do individuals or populations evolve? Eastern Meadowlark Western Meadowlark

Many factors can affect speciation Many factors can affect speciation. (the formation of a new species) But first, populations must be isolated

There are two ways to isolate a population geographically isolated reproductively isolated isolated populations evolve independently based on the conditions they are living in.

Chemical Changes to DNA Small isolated populations Forces of Evolutionary Change So once a population has been isolated….what mechanisms can cause evolution to occur? Gene Flow Genetic Drift Mutation Migration Chemical Changes to DNA Small isolated populations Non-random mating Selection Pressure Natural Selection Sexual Selection

Patterns of Evolution Different patterns of evolution occur in different environments Convergent evolution Divergent evolution (also called adaptive radiation) Coevolution

Convergent Evolution unrelated species When unrelated species live in similar environments in different parts of the world similar environmental pressures similar pressures of natural selection unrelated species

CONVERGENT EVOLUTION EXAMPLE http://evolution.berkeley.edu/evolibrary/home.php Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

common ancestor Adaptive radiation is a type of divergent evolution populations that were once similar change and adapt to different living conditions common ancestor

Adaptive Radiation Example When one species splits into many species to fill open habitats. Darwin’s finches 25

Coevolution Two or more species reciprocally affect each other’s evolution predator-prey disease & host competitive species mutualism pollinators & flowers