The History of Evolution
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The History of Evolution. Darwin. Lamarck. Cuvier. lion. Species. Species : group of organisms that can interbreed and produce fertile offspring Different species rarely breed Interspecies breeding often results in sterile offspring Ex: Horse x Donkey = Mule Ex: Lion x Tiger = Liger

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The History of Evolution

Darwin

Lamarck

Cuvier


Species

lion

Species

  • Species: group of organisms that can interbreed and produce fertile offspring

    • Different species rarely breed

    • Interspecies breeding often results in sterile offspring

      • Ex: Horse x Donkey = Mule

      • Ex: Lion x Tiger = Liger

    • New species = when unable to successfully reproduce

      • Are horses & donkeys a different species even though they can produce offspring?

tiger

liger


horse

donkey

mule


Jean Baptiste

de Lamarck

  • Acquired Inheritance: Early theory where organisms could acquire and pass traits after birth

  • Cause: environmental changes forced individuals to change

  • Problem: Traits acquired after fertilization cannot be passed to offspring

  • Early Belief: Giraffes & Long Necks

    • Long necks are result of stretching to reach leaves

    • Extra length was passed on to offspring


Geologic change
Geologic Change

  • Early belief:

    • Earth ~6,000 years old

    • Life remained unchanged

  • “New” Observations

    • Rock layers (strata) contained differing fossils

    • Deeper fossils (older) less complex

    • Environmental changes thought to affect life characteristics

    • Uniformitarianism: geologic processes that shape earth are uniform


Charles darwin
Charles Darwin

  • Observed:

    • Organisms have variations based upon environment

    • Similarities between extinct fossils & modern life

    • Marine fossils atop mountains

  • Natural Selection: Process where organisms with favorable traits survive and reproduce

  • Major concept in biology published in The Origin of Species (1859)


Adaptation variation

Variation: Inherited traits that make an individual different from others

Green, flat wings of the insect above

Adaptation: Variation increases the chance of survival

Ability to blend with environment

Adaptation & Variation


Butterflies won't

lay eggs on plants

with fake egg spots


Can you find

the geckos?



Causes of genetic variation
Causes of Genetic Variation

  • Genetic variation increases chances some survive changing environments

  • Gene Pool: All alleles within a population

  • Two main causes of genetic variation:

    1) Mutations: Random genetic changes may affect phenotypes

    2) Recombination: During meiosis, genes recombine in varying patterns


Variation 4 different gametes
Variation: 4 Different Gametes

Chromatids

copied

Crossing-

over

Crossing-

Over

finished

Genetic variation!

Four differing chromatids


Quick Review

  • Features of a species can evolve, or change over time

  • Natural selection is when favorable traits allow survival & reproduction

  • Variations allow an organism to be better suited to its environment


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