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Evolution

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Title: Evolution


1
Evolution
2
The History of Life
3
Early history of Earth
  • Earth is thought to have formed about 4.6 billion
    years ago.
  • It began as a hot ball of rock.
  • Meteorites bombarded its surface.
  • Volcanoes shook the planet shot out gases that
    formed an atmosphere.

4
Early history of Earth
  • About 3.9 billion years ago, the Earth cooled
    enough for water vapor to condense.
  • Violent rainstorms occurred the oceans formed.
  • About 3.5 billion years ago, the first living
    organisms appeared.

5
Early history of Earth
6
Fossils
  • Oldest rocks are about 3.9 billions years old.
  • Fossils
  • Any evidence of an organism that lived long ago.

7
Paleontologists
  • Scientists who study ancient life

8
Relative dating technique
  • Based on the premise that the deeper an organism
    is buried in sediment, the older it is.

9
Relative dating technique
10
Radiometric dating technique
  • Involves using radioactive isotopes that give off
    radiation and form a different element.
  • Scientists determine the ages of rocks/fossils by
    comparing the amount of the original radioactive
    element to the amount of the new element formed
    from decay.

11
Radiometric dating technique
12
Radiometric dating technique
  • Example K-40 (potassium-40) decays to form
    Are-40 (Argon-40) in 1.3 billion years.

13
Geologic time scale
  • A type of calendar that allows scientists to
    communicate about events that have occurred since
    Earth was formed.
  • Based on the different types of living organisms
    that have appeared during Earths history.

14
Geologic time scale
  • The scale is divided into 4 eras
  • Precambrian
  • Paleozoic
  • Mesozoic
  • Cenozoic
  • These 4 eras are then subdivided into periods.

15
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16
Precambrian era
  • Contains the oldest evidence of life (around 3.5
    billion years old).
  • Prokaryotes simple eukaryotic organisms (algae,
    sponges jellyfish).

17
Precambrian era
18
Paleozoic era
  • Invertebrates (worms primitive arthropods)
  • Fishes (earliest vertebrates)
  • Plants
  • Amphibians
  • Reptiles

19
Paleozoic era
20
Mesozoic era
  • Dinosaurs
  • Mammals
  • Flowering plants

21
Cenozoic era
  • Mammals flourished.
  • Primates evolved.

22
Spontaneous generation
  • The idea that life was produced from nonliving
    matter.

23
Francisco Reid
  • In 1668, he disproved the theory of spontaneous
    generation of larger organisms.
  • People still believed that microorganisms arose
    spontaneously from a vital force in the air (air
    theory).

24
Louis Pasteur
  • In the mid-1800s, he disproved the air theory
    and established the concept of biogenesis.



25
Biogenesis
  • The idea that living organisms come only from
    other living organisms.

26
Alexander Oaring
  • In the 1930s, he hypothesized that life began in
    the early oceans.
  • He suggested that energy from the sun and
    lightning triggered chemical reactions with the
    primitive atmosphere. The products rained down
    into the oceans to form primordial soup.

27
Oparins molecules
28
Evolution of cells
  • First forms of life were anaerobic, heterotrophic
    prokaryotes, which probably evolved from some
    type of protocell.
  • Competition for nutrients by heterotrophic
    prokaryotes led to the evolution of the first
    autotrophs (similar to archaebacteria).

29
Evolution of cells
  • Photosynthesizing prokaryotes evolved next, which
    increased the oxygen concentration in Earths
    atmosphere.
  • Aerobic respiration evolved with the increase of
    oxygen.

30
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31
The Theory of Evolution
32
Charles Darwin
  • English scientist who is considered the founder
    of modern evolutionary theory.
  • In 1831, he sailed on the HMS Beagle to South
    America the South Pacific.
  • On the Galapagos Islands, Darwin studied
    compared the anatomy of many organisms.

33
Charles Darwin
  • Darwin used his theory of natural selection to
    explain how organisms evolve.

34
Natural selection
  • A mechanism for change in populations that occurs
    when organisms with favorable variations for a
    particular environment survive, reproduce and
    pass these variations on to the next generation.

35
Natural selection
  • Those with less favorable variations are less
    likely to survive and pass on traits to the next
    generation.
  • Each new generation is largely made up of
    offspring from parents with the most favorable
    variations.

36
Natural selection
  • Natural selection is also known as the survival
    of the fittest.

37
Evidence for evolution
  • The following provide evidence for evolution
  • Fossils
  • Anatomical studies
  • Embryological development
  • Biochemistry

38
Fossil evidence
  • Scientists use fossil records to understand the
    general pathway of evolution.

A model of evolution from small-toed to
one-toed horses.
39
Anatomical studies
  • A homologous structure is a modified structure
    that is seen among different groups of
    descendents.

40
Anatomical studies
  • An analogous structure is any body part that is
    similar in function but different in structure.
  • Example Insect and bird wings have the same
    function but are not similar in structure (bird
    wings are made up of a set of bones while insect
    wings are mainly made of chitin).

41
Anatomical studies
  • A vestigial structure is any body structure that
    is reduced in function in a living organism but
    may have been used in an ancestor.

Pelvic bones of a baleen whale.
42
Embryological development
  • In the earliest stage of embryological
    development in a fish, reptile, bird and mammal,
    a tail and gill slits can be seen in all species.
  • As development continues, the embryos become more
    more distinct, in the stages before birth,
    they attain their distinctive forms.

43
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44
Biochemistry
  • Scientists use DNA, RNA and proteins to determine
    levels of relationships among species within
    major taxonomic groups.

45
The Evolution of Species
46
Types of selection
  • Natural selection acts upon the variation in
    populations.
  • There are 3 types of selection
  • Stabilizing selection
  • Directional selection
  • Disruptive selection

47
Stabilizing selection
  • The type of natural selection that favors average
    individuals in a population.
  • Large spiders are at a disadvantage b/c they can
    be seen captured more easily.
  • Small spiders might not be able to catch enough
    prey to survive reproduce.
  • Average-size spiders are just right.

48
Directional selection
  • When one of the extreme forms of a trait is
    favored by natural selection.
  • Woodpeckers feed by pecking holes in trees to get
    insects that live under the bark.
  • One year, the trees are invaded by a species of
    insect that lives deep within the trees.
  • Woodpeckers with long beaks have the selective
    advantage over those with short or average-size
    beaks.

49
Disruptive selection
  • Individuals with either of 2 extreme forms of a
    trait are at a selective advantage.
  • Limpets are shell-covered marine organisms that
    live attached to rocks.
  • On light-colored rocks, white-shelled limpets are
    able to blend in with the rock.
  • On dark-colored rocks, dark-colored limpets are
    able to blend in with the rock.
  • Tan-colored limpets, the intermediate forms, are
    easily spotted on either color rock.

50
Speciation
  • It is the process by which a new species is
    formed.
  • This can only occur when either interbreeding or
    the production of fertile offspring is somehow
    prevented.
  • Isolation can cause speciation.

51
Types of isolation
  • Geographic isolation occurs if a physical barrier
    separates a population into groups.
  • Reproductive isolation occurs when formerly
    interbreeding organisms are prevented from
    producing fertile offspring.

52
Speciation rates
  • Gradualism is the idea that species originate
    through a gradual buildup of new adaptations.
  • It is supported by fossil evidence, such as those
    for the slow steady buildup of adaptations of
    camels horses.

53
Speciation rates
  • Punctuated equilibrium states that speciation
    occurs quickly in rapid bursts, with long periods
    of stability in between.

54
Patterns of evolution
  • Divergent evolution is the pattern of evolution
    in which species that once were all similar to
    the ancestral species become more and more
    distinct.
  • Human feet are different from monkey feet because
    humans began to walk upright on the ground rather
    than swinging through the trees.

55
Patterns of evolution
Monkey feet
Human feet
56
Patterns of evolution
  • Convergent evolution is the pattern of evolution
    in which distantly related organisms evolve
    similar traits.
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