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Evolution of Populations

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Evolution of Populations Chapter 16 (M) – PowerPoint PPT presentation

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Title: Evolution of Populations


1
Evolution of Populations
  • Chapter 16 (M)

2
  • Evolution ? a continuing process of change in a
    population of organisms over long periods of time

3
History
  • 1700s? Scientists believed that Species are
    Fixed and do not change
  • Mid 1700s? fossil records lead Georges Buffon to
    say
  • Earth is older than 6000years
  • Different species arose from variation from a
    common ancestor
  • 1800s? Lamarck explained fossil records species
    diversity

4
Lamarck
  • Proposed the theory of Inheritance of Acquired
    Characteristics? body changes developed during
    an organisms life time could be passed on to the
    offspring

5
Short neck? ate up grass? had to stretch neckto
reach trees

6
Lamarck
  • Acquired characteristics would have to modify DNA
    to be inherited? no evidence of this
  • Lamarcks theory was rejected
  • Set the stage for Darwin

7
  • Variation in the population? long short necks
  • Long necked survived? reproduced? population was
    gradually changed to long necked animals

8
Darwin(1809-1882)
  • Started his voyages at the age of 22 on the HMS
    Beagle
  • Was responsible for collecting specimens of
    fossils
  • He was aware of geological formations of land
    masses? could explain fossils of snails from
    mountains
  • Studied his collections for the next 22 years

9
Darwins Key Observations
  1. Fossils fossil records show that organisms ?
    simpler ? complex
  2. Overproduction of offspring
  3. Limited supply of resources in an environment
  4. Survival in a limited environment depends in part
    on features inherited from parents

10
Information that influenced Darwin
  • Charles Lyell? geologist proposed that the Earth
    was very old and had slowly been changing for
    millions of years
  • Thomas Malthus ? economist ? social problems as a
    result of the exponential growth of the human
    population
  • Artificial selection by breeders

11
Darwin Concluded
  1. Descent with Modification
  2. Natural Selection

12
Descent with Modification
  • All present day organisms are related through
    descent from unknown ancestors in the past.
  • These descendants of earliest organisms spread
    into different habitats? adapted to diverse ways
    of life

13
Natural Selection
  • Individuals whose inherited characteristics adapt
    them best to their environment are most likely to
    survive and reproduce
  • Basic Mechanism of Evolution? Natural Selection

14
Natural Selection
  • Occurs over a vast period of time
  • Individuals undergo selection, but do not evolve?
    Populations Evolve

15
Evidence of Evolution
  • Section 16.4(M)

16
Evidence
  1. Fossil Records
  2. Comparative Anatomy
  3. Embryonic Structures
  4. DNA Homology

17
Fossils
  • Remains, traces or imprints of an organism
    preserved in the earths crust
  • Imprint
  • Mold
  • Cast
  • Petrified

18
Fossil Records
  1. Fossils the order in which they appear in
    layers of rocks
  2. Fossil records show that animals plants have
    appeared in a historical sequence, fossils found
    in rocks of different ages differ because life on
    Earth has changed through time

19
Each Layer represents a particular time period
20
Comparative Anatomy
  • The comparison of body structures in different
    species
  • Homologous Structures
  • Analogous Structures
  • Vestigial Structures
  • Ex common descent? evident in anatomical
    similarities between species in the same
    taxonomic group

21
Homologous Structures
  • Structures that are similar have been derived
    from a common ancestor, but have been adapted to
    different functions.
  • ex humans, cats, whales, bats? all mammals
  • Whales flipper does not have the same function
    as a bats wing

22
Homologous Structures
23
Analogous Structures
  • Body parts similar in function but have different
    structures
  • Ex wings of insects and birds

24
Vestigial Structures
  • Body parts reduced in size appear to serve no
    function

25
Embryonic Structures
  • Embryos of closely related organisms often have
    similar stages in development

26
DNA Homology
  • Comparison of genes and proteins shows the
    relationships between species

27
Darwins Natural Selection A Mechanism of
Evolution
28
Natural Selection
  • Regional and timely
  • Adapts organisms to their local environment
  • Environmental factors vary from place to place
    time to time? adaptation in one situation may be
    useless in another
  • Example Biston betularia? peppered moth

29
Peppered Moth
  • England ? two varieties? dark light
  • 1850? almost all were light? industrial
    revolution? pollution? tree trunks turned black?
    light moths became easy prey
  • Dark survived reproduced
  • End of century ? almost all were dark

30
Biston betularia peppered moth
31
Populations
  • A group of individuals of the same species living
    in the same place at the same time
  • Mainland animal species colonizes a chain of
    distant and isolated islands? separate
    population.
  • These populations adapt to their local
    environments.
  • Over time, the isolated populations would become
    more and more different.
  • And over many generations, the populations could
    become different enough to be separate species.

32
Darwins Finches? adapted to different food
sources ?beak Structures
33
Variation
  • Differences among members of the same Species

34
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35
Adaptation
  • Inherited trait that Improves the Chances Of
    Survival Reproduction
  • Structural? mimicry? organism copies the
    appearance of another species
  • Physiological? changes in the organisms metabolic
    process? penicillin? drug resistant bacteria
  • Behavioral? inherited behavior pattern that
    allows organism to survive

36
Adaptation- Mimicry
  • Monarch? tastes bitter? birds avoid them because
    they get sick
  • Viceroy(extra black lines on wings)? not bitter,
    look act like Monarchs ?birds avoid them

37
Adaptation Camouflage
  • Protective adaptation that allows an organism to
    blend into its surroundings
  • The better the camouflage, the more likely it is
    for the organism to survive and reproduce

38
Adaptation Camouflage
39
Artificial Selection
  • Selective breeding of domesticated plants and
    animals to produce offspring with genetic traits
    that humans value.

40
From Wild Mustard to our Table
41
Pesticides- Natural Selection in Action
  • Spraying crops ?kill insect pests? favored the
    reproduction of insects with inherited resistance
    to the poisons
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