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Evolution

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Evolution All the changes that have transformed life from its earliest forms to what we see today. Evolution is the result of genetic changes that occur in constantly ... – PowerPoint PPT presentation

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Title: Evolution


1
Evolution
  • All the changes that have transformed life from
    its earliest forms to what we see today.

2
Evolution is the result of genetic changes that
occur in constantly changing environments.
3
Natural Selection
  • Populations change in response to their
    environment.
  • Acts on phenotype of an organism.
  • (Not genotype)

4
Natural Selection
  • Determines the differential survival of groups of
    organisms

5
Phenotype
  • Observable characteristics
  • (green eyes, brown hair, purple flowers, etc.)

6
Genotype
  • Genetic makeup of an organism determined by a
    pair of alleles.

7
Allele
  • Alternative form of a gene for each variation of
    a trait.

8
Gene
  • Unit of hereditary information
  • Located on a chromosome
  • Contains DNA

9
Gene Pool
  • Total genes in a population at any one time

10
Homozygous
  • Having two identical alleles for a trait

11
Heterozygous
  • Having two different alleles for a trait

12
Mutation
  • Change in DNA of a gene or chromosome
  • Mutations occur constantly in a gene pool

13
Reproductive Isolation
  • Prevention of mating between formerly
    interbreeding groups.
  • or
  • The inability of these groups to produce fertile
    offspring

14
Geographic Isolation
  • Physical barrier divides a population
  • These two groups are not able to mate
  • gt may lead to new species

15
Speciation
  • Formation of a new species

16
Mass Extinction
  • An episode in which many species suddenly become
    extinct

17
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18
Punctuated Equilibrium
  • Evolutionary model
  • Rapid changes to a species in a short time,
    followed by periods of little change.

19
Gradualism
  • Model of evolution involving slow, gradual
    changes to a species over time.

20
Gradualism vs. Punctuated Equilibrium
21
Bacteria
  • First form of life on Earth
  • Evolved 3.5 billion years ago (prokaryotes)
  • Eukaryotes (complex) formed 1.5 billion yrs ago

22
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23
Multicellular life
  • Evolved 570 Ma (Cambrian explosion of life!)
  • Multicellular more than one cell
  • Jellyfish-type creatures were first forms

24
Vertebrates
  • Have a backbone
  • 1st were jawless fish
  • Amphibians 1st on land
  • Almost all land animals larger than a fist

25
Arthropods
  • Have an exoskeleton
  • (Hard outer shell)
  • First animals on land (scorpion)
  • Crabs, lobsters, insects, spiders

26
Reptiles
  • Evolved from amphibians
  • Diversified into many forms after the Permian
    mass extinction (250 Ma).

27
Dinosaurs
  • Evolved from reptiles and dominated the Mesozoic
    Era
  • Were wiped out by a large body that impacted
    Earth 65 million yrs ago

28
Mammals
  • Were very small during the Mesozioc
  • Became the dominant life form after the
    Cretaceous mass extinction (65 Ma)
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