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Evidence for Evolution. Fossils. Evidence for evolution. Fossils. Show: Evolution Primer: How do we know evolution happens?. Evidence for evolution. DNA All life uses the same 4 DNA bases: thymine, adenine, guanine, cytosine

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Evidence for Evolution

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Evidence for evolution

Evidence for Evolution



Evidence for evolution1

Evidence for evolution

  • Fossils

Evidence for evolution

  • Show: Evolution Primer: How do we know evolution happens?

Evidence for evolution2

Evidence for evolution

  • DNA

  • All life uses the same 4 DNA bases: thymine, adenine, guanine, cytosine

  • Biochemical pathways trace evolutionary relationships just as fossils do

Evidence for evolution3

Evidence for evolution

  • Sense of smell

  • All mammals have many genes for smell—about 3 % of all their genes

  • In humans, that’s about 1,000 genes.

    • BUT 300 genes in humans are useless-DO NOT work

    • WHY?

  • Whales, dolphins also have odor genes useful in air, but not water

    • BUT: NONE of the genes in whales and dolphins works. Whale’s blowhole is used for breathing, not smelling.

Evidence for evolution4

Evidence for evolution

  • Homology: characteristics that organisms share from a common ancestor

  • Good example: limbs of tetrapods

Evidence for evolution5

Evidence for evolution

  • Biogeography: the geographic distribution of species tells stories that geology and evolution can shed light on

  • e.g.: Dinosaurs that can’t swim, but are found on several continents  says those continents were once connected

Evidence for evolution

The finches on the Galapagos are thought to have evolved from a single species of ancestral finch, probably the generic sort of seed-eating finch shown in the center. When a population of finches was reproductively isolated on one of the islands, it adapted over time to feed on a new food source. After time, it was sufficiently different from its ancestor to be considered a new species.

Evidence for evolution6

Evidence for evolution

  • Artificial selection

    • Humans can mimic the selection process, bend evolution to our will (sometimes!!) and produce useful plants and animals.

    • Check out corn (teosinte)



  • Traits that are successful in their environment

  • An adaptation to one environment may be NEUTRAL or UNFAVORABLE in another environment

  • May be simple—heavier coat in colder climate—or complex—the mammalian eye



  • Adaptations are specific to the environment.

    • A zebra’s coat pattern is camouflage in the African savannah. It would not be advantageous in a North American grassland.

    • Running speed is advantageous for a cheetah on the savannah. But cats in the rainforest (e.g., jaguar) are not fast. Strength and stealth are more important than speed there.

Adaptation examples mimicry

How could such mimicry evolve?

What is the advantage to the orchid?

Is there a cost or benefit to the wasp?

Some orchids (a kind of flower) mimic wasps. They look enough like a female wasp to fool males into ``mating’’ with them and thus transfer their pollen

Adaptation examples: mimicry

Adaptation examples more mimicry

Adaptation examples: more mimicry

  • Katydids have evolved a body form that looks like a leaf.

  • Why? What is the advantage to the katydid?

Adaptation examples still more mimicry

Adaptation examples: still more mimicry

  • Non-poisonous king snakes mimic poisonous coral snakes

  • Many examples of mimicry in nature



  • One species evolves into another OR splits into two.

  • How can this happen?

    • Geographic isolationallopatric speciation

Biodivrsity patterns hotspots

Biodivrsity patterns: hotspots

Birds in south america

Birds in South America

History of life

History of life

  • As previous picture shows:

    • Complex creatures and structures have evolved

    • But simple life forms still common and dominate in many habitats ``Earth still belongs to the bacteria’’

    • Speciation generates diversity; extinction reduces it



  • The disappearance of a species from Earth

  • Local disappearance is called extirpation

Evidence for evolution

  • 99% of ALL species that have ever existed are extinct



  • Two kinds:

  • Background: the regular, consistent, extinction of species over millions and hundreds of millions of years

    - Result of environmental change, species interactions

  • Mass: the relatively sudden extinction of a great number of species in a short period of time (few million years, or less)

Evidence for evolution

This graph shows extinction rates. You can see that five times in the last 600 million years, the rate has spiked up. Those are MASS EXTINCTIONS. The last one is when the dinosaurs died. Between mass extinctions, there is a more steady extinction rate, called BACKGROUND EXTINCTION.

6 th mass extinction

6th mass extinction?

  • We are in the midst of a 6th mass extinction.

  • First one caused by human activity.

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