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EVOLUTION

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Title: THE THEORY OF EVOLUTION Author: Chicago Public Schools Last modified by: Kaplan, David B Created Date: 3/12/2009 4:45:28 PM Document presentation format – PowerPoint PPT presentation

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Title: EVOLUTION


1
EVOLUTION
  • CHAPTER 15

2
Natural Selection the Evidence for Evolution
  • Ch. 15, Sec. 1

3
Evolution
  • Gradual change in a species over time due to
    adaptations,
  • There are exceptions
  • Science is Tentative
  • Development of new organisms from preexisting
    types of organisms
  • Living things come from other living things
  • New species come from other species

4
  • Characteristic changes in a population involve
    changes to genes
  • These changes then get passed along through the
    genes
  • Who do you get your genes from?
  • Supported by a lot of evidence and data
  • Fossil, Anatomical, DNA

5
Charles Darwin (1809-1882)
  • Started off studying medicine
  • 1831 signed on for a 5 year journey of South
    America on the HMS Beagle
  • Enjoyed nature making observations
  • Noticed similar looking organisms on different
    continents

6
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7
Darwins Clues
  • Collected fossils
  • Observed the adaptations of plants animals
    allowing them to survive in particular
    environments
  • Adaptation a trait (which is coded for by DNA
    in a gene) that allows an organism to be
    successful in its environment
  • Like tools that help them get the job done

8
How are these organisms adapted to their
environment?
9
Galapagos Islands
  • One of Darwins stops on the Beagle
  • Group of volcanic islands off the west coast of
    South America

10
  • Home to several species of finches
  • Each species is adapted to the type of food eaten

11
Darwins Hypotheses
  • Darwin hypothesized that all the species
    descended from ancestral finches
  • The ancestral finches flew to the Galapagos
    Islands over from mainland South America
  • Population changed over time to adapt to the
    environment

12
Darwins Observations
  • 1. Overproduction
  • Most species produce large numbers of offspring
    (ex rabbits)
  • But why isnt the earth overrun by rabbits?
  • The environment will set a limit on how big the
    population gets by causing deaths or limiting
    births
  • 2. Competition within a species.

13
Observations cont.
  • 3. Variation
  • Within populations organisms have different
    traits because of variations in genes
  • Variations can be inherited (who do you get your
    genes from?)
  • Populations have multiple alleles for any given
    trait (dark fur/light fur, tall ears/short ears,
    etc.)

14
In summary
  • Organisms that have superior traits/tools are
    better adapted
  • Therefore theyre more likely to survive
  • Therefore theyre more likely to reproduce and
    pass on the genes for the superior traits/tools
  • What chooses the superior traits?

15
ArtificialSelection
  • Darwin worked with breeding different variations
    on pigeons
  • Artificial Selection humans select good traits
    in organisms to breed
  • Ex prettier roses, bigger chickens, sweeter
    oranges
  • YOU see it all the time
  • Darwin hypothesized
  • Something like Artificial Selection must be
    acting on the organisms living in the wild

16
Natural Selection
  • Natural Selection mechanism for change in
    populations organisms with favorable variations
    survive, reproduce, pass on the variation to
    the next generation (offspring)
  • Organisms with the best adaptations (helpful
    traits, good tools) are most likely to survive
    reproduce
  • Through inheritance the adaptations will become
    more frequent in the population

17
Who gets to evolve?
  • It is the population that evolves, not the
    individual
  • If you like swimming, can you choose to evolve
    gills?
  • An individual can be born with a mutation
  • If the mutation is an advantage (good tool) for
    living in a particular environment then that
    individual will be more likely to survive pass
    on that mutation to its offspring

18
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19
Structural Adaptations
  • Why are these structures adaptations?

20
  • Mimicry structural adaptation allowing one
    species to resemble another species

21
  • Camouflage adaptations allows species to blend
    in with surroundings

22
Rapidly Developing Physiological Adaptations
  • Evolution is not always a slow process
  • Evident in antibiotic resistance (bacteria evolve
    too)

23
  • Resistance of insects to pesticides

24
  • Increased toxicity of snake poison

25
Fossil Evidence
  • Fossils show that over time species have
    gradually changed their form
  • A transitional species will have characteristics
    of both the ancient and modern organism
  • There has to be something in between
  • Ex Do children automatically become adults?
  • Ex Modern whales evolved from an ancient, land
    mammal

26
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27
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28
Anatomy Evidence
  • Studying anatomy can uncover structural evidence
    of a common ancestor
  • Homologous Structure similar in build,
    different function anatomical structures in
    different species inherited from a common ancestor

29
Homologous Structures
  • An early ancestor of all 4 species had a forelimb
    with similar structure (common ancestor)

30
Analogous Structures
  • Have closely related functions, but are built
    differently does not indicate a common ancestor

31
  • Vestigial Structures serve no function but
    resemble structures with functional roles in
    other animals

32
Embryology
  • Embryology the study of how organisms develop
  • Early stages of vertebrate embryos look very
    similar
  • As development continues embryos of different
    species start looking less alike

33
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34
DNA Evidence
  • All living organisms have DNA in common
  • DNA codes for proteins
  • The more closely related two species are.
  • The more similar their DNA.
  • The more similar the proteins made in their
    bodies are

35
Mechanisms of Evolution
  • Ch. 15, Sec. 2

36
Population Genetics
  • Gene Pool all the alleles for a particular
    trait in a population are pooled together
  • ex all the alleles for short fur and long fur,
    all the alleles for brown fur and black fur
  • Allelic Frequency percentage of a specific
    allele in the gene pool
  • of brown fur alleles of black fur alleles
  • Genetic Equilibrium maintaining the same
    frequency of alleles over time

37
Hardy-Weinberg Equation - can be used to measure
whether the observed genotype frequencies in a
population differ from the frequencies predicted
by the equation.
  • pq1 p22pqq21
  • pDOMINANT ALLELE (A)
  • qrecessive allele (a)
  • p2HOMOZYGOUS DOMINANT (AA)
  • 2pqHeterozygous (Aa)
  • q2homozygous recessive (aa)

38
Conditions for H-W to occur
  • Large Population
  • Isolated (no immigration or emigration)
  • No Mutations
  • Random Mating
  • No Natural Selection

39
Changes in Genetic Equilibrium
  • Mutations can cause variations to be added to the
    gene pool of a population
  • Genetic Drift chance events changing a
    populations genetic equilibrium

40
Natural Selection Acts on Variations - red
(before) blue (after)
  • Stabilizing selection natural selection that
    favors average individuals in a population

41
Natural Selection Acts on Variations - red
(before) blue (after)
  • Directional selection natural selection favors
    one of the extreme variations of a trait

42
Natural Selection Acts on Variations - red
(before) blue (after)
  • Disruptive selection individuals with either
    extreme of a traits variation are selected for

43
Evolution of a Species
  • Changes to a gene pool can lead to the evolution
    of a new species
  • Speciation members of similar populations can
    no longer interbreed

44
Biogeography Field Video
  • Geological Isolation physical barriers divide a
    population
  • ?
  • Over time, the ? divided populations may become
    two species that can no longer interbreed, even
    if reunited

45
Reproductive Isolation
  • Occurs when formerly interbreeding organisms can
    no longer mate and produce fertile offspring 2
    types
  • 1. Genetic Isolation genes of two populations
    are so different they cannot produce fertile
    offspring
  • 2. Behavioral isolation (ex one population
    mates in the spring, another population mates in
    the fall)

46
  • Change in Chromosome Numbers mistakes in cell
    division lead polyploid individuals (abnormal
    sets of chromosomes)
  • Polyploids can be sterile, unable to reproduce
  • Polyploids can also reproduce and generate a new
    species through interbreeding

47
Speciation Rates
  • Gradualism species originate through gradual
    change of adaptations
  • Punctuated Equilibrium speciation occurs in
    quick, rapid bursts
  • The fossil record supports both

48
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49
Patterns of Evolution
  • Divergent Evolution species that were once
    similar evolve to look differently
  • Adaptive Radiation ancestral species evolving
    to fit into a lots of different habitats

50
Field Museum Video
  • Convergent Evolution very distantly related
    organisms evolving similar traits

51
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52
  • Hummingbird moths are night-flying insects whose
    behavior and appearance are similar to those of
    hummingbirds. Explain how these two organisms
    demonstrate convergent evolution and analogous
    structures.
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