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Evolution

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Evolution Evidence of Evolution Homologous structures = structures that have different mature forms but develop from the same embryonic tissue Evidence of Evolution ... – PowerPoint PPT presentation

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Title: Evolution


1
Evolution
2
Evolution
Modern Humans
  • Definition Change in a population of organisms
    over time.
  • Human evolution illustrated on a cladogram

3
Theories of Evolution
  • Jean-Baptiste Lamarck 1809 published his theory
    of evolution
  • Mechanism of Evolution Inheritance of Acquired
    Characteristics

4
Theories of Evolution
  • Charles Darwin 1859 published his theory of
    evolution in the major work, On the Origin of
    Species
  • Mechanism of Evolution Natural Selection

5
The Original Manuscript
  • Most important book on biology ever published!

6
Lamarcks Ideas
  • Organisms change over time
  • Organisms are adapted to their environment
  • They are continually changing and acquiring
    features more suitable for their environment.
  • Continued ?

7
Larmarcks Ideas
  • During an organism's lifetime, there is selective
    use or disuse of its organs and traits. If a
    trait isnt used?its lost.

8
Larmarcks Ideas
  • Traits that are used are passed on to their
    offspring. Over time, this process leads to the
    change in a species. (hence the term
    inheritance of acquired characteristics)

9
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10
Darwins Ideas on Evolution
  • Variation organisms show variation in each of
    their traits height, colors of eyes/hair/skin,
    resistance to disease, etc.
  • Natural selection Organisms better suited to
    their environment survive and reproduce (also
    known as survival of the fittest).
  • Fitness ability to survive and leave offspring.
    No offspring No fitness.

11
Worksheets
  • Natural Selection and fur color
  • Evolution comparison of Lamarck (acquired
    characteristics) and Darwins (natural selection)
    ideas on evolution.

12
Darwins ideas on Evolution
  • In the early 1800s, when Darwin was born, people
    thought the Earth was a few thousand years old.
  • But by the 1820s, scientists hypothesized the
    Earth was millions of years old.
  • 5000 years
  • 5,000,000 years

13
Darwins ideas on Evolution
17-11 MYA
5 MYA-present
  • An ancient Earth was necessary to support
    Darwins ideas on evolutionpopulations change
    over (long, long periods of) time.

35,000,000YA
12-6 MYA
55,000,000YA
14
Microevolution according to Darwins Ideas on
Natural Selection
Natural Variation in population of bacteria
15
Macroevolution according to Darwins Ideas on
Natural SelectionSpeciation formation of new
species
16
Genes and Variation
  • Most phenotypes (traits) are polygenic.
  • A graph of these traits often shows a bell curve.

17
Stabilizing Selection
  • If individuals near the center of the bell curve
    have higher fitness ( leave a greater amount of
    fertile offspring) then stabilizing selection
    occurs.

18
Directional Selection
  • If individuals at one end of the bell curve have
    higher fitness then directional selection occurs.

19
Disruptive Selection
  • If individuals at both ends of the curve have
    higher fitness than those in the middle then
    disruptive selection occurs.

20
Genetic Drift
  • If a small population is isolated from others of
    the same species, it is possible that just be
    chance one allele may become more common in a
    population.

21
Genetic Drift
  • For example The Bronx, NY, becomes built up and
    trees are cut down. Few squirrels are able to
    survive. However, one section of the Bronx is
    set aside for the development of the Bronx Zoo.
    Trees are NOT cut down in this area. By chance,
    several of the gray squirrels in the area of the
    zoo have black fur (a variation in fur color).
    Over time, the allele for black fur becomes
    common in this population.

22
How do new species form?Example Galapagos
Finches
  • A small group of a species of finch arrives on
    one of the Galapagos Islands
  • These finches do not usually fly across open
    waterthey may have gotten lost or were blown
    there by the wind.

23
Speciation continued!
  • Over time these original finches may have ended
    up on other of the Galapagos Islands through some
    chance occurrence.
  • USUALLY the finches do NOT fly from one island to
    another.

24
Speciation continued!
  • The Galapagos Islands had different environments.
  • Some had a low elevation and were dry with little
    plant material.

25
Speciation continued!
  • Others had a higher elevation with greater
    rainfall and many plants.

26
Speciation continued!
  • Directional selection occurs
  • One island may have seeds that are large and
    difficult to open.
  • Birds with a larger, thicker beak will have the
    highest survival rate on this island

27
Speciation continued!
  • Directional selection occurs
  • Another island may have seeds that are small and
    easy to open
  • Birds with a small, thinner beak will have the
    highest survival rate on this island

28
Speciation continued!
  • Reproductive Isolation if the populations
    remain separate, and their gene pools continue to
    change, eventually they can no longer mate with
    each otherthey are then TWO NEW SPECIES!!!
  • On the Galapagos Islands this processes resulted
    in the evolution of 13 different finch species.

29
  • Darwins Finches

30
Evidence of Evolution
  • Fossil Record

31
Evidence of Evolution
  • Comparative Anatomy
  • Homologous structures structures that have
    different mature forms but develop from the same
    embryonic tissue

32
Evidence of Evolution
  • Vestigial organ organ that serves NO useful
    function in an organism.
  • Wisdom teeth
  • Appendix

HUMANS
Fingernails on Seals Fin
33
Embryology
NOTE Similarity of embryos of all of these
animals
34
Evidence of Evolution
  • Similarities and dissimilarities in DNA code.
  • Complete worksheet bar graph.
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