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Chapters 22-25 Evolution

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Title: Chs. 14-16: Evolution Author: Brandon Spencer Last modified by: Box Elder School District Created Date: 2/4/2001 10:31:28 PM Document presentation format – PowerPoint PPT presentation

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Title: Chapters 22-25 Evolution


1
Chapters 22-25 Evolution
2
Evolution
  • The definition of Evolution is
  • change over time
  • Biological Evolution is
  • genetic change in population over time
  • process by which modern organisms have descended
    from ancient organisms (slow change over long
    time)
  • Even relatively quick evolution takes hundreds of
    thousands of years

3
History of Evolutionary Theories
  • Plato (427-347 B.C.) 2 worlds 1 perfect, 1
    imperfect. No change in organisms
  • Aristotle (384-322 B.C.) Organisms placed on
    ladder of complexity / perfection (scala
    naturae) No change
  • Judeo-Christian culture tried to explain the
    Creators plan as observable, natural phenomena
    Natural Theology

4
History of Evolutionary Theories
  • Carolus Linnaeus (1707-1832) Designed modern
    taxonomic system (binomial nomenclature)
  • From this system, we can (he didnt) now infer
    evolutionary relationships between different
    groups
  • Geologists
  • Georges Cuvier
  • James Hutton
  • Charles Lyell

5
History of Evolutionary Theories
  • Georges Cuvier (1769-1832) helped develop
    Paleontology study of fossils
  • Discovery of fossils (extinct species,
    similarities to modern species) put some doubt
    into Earths age and the origin of species
  • Cuvier explained differences in strata with
    catastrophism floods, droughts, volcanoes,
    etc. changed local areas drastically over short
    periods of time
  • Organisms did not change, just migrate

6
History of Evolutionary Theories
  • James Hutton (1726-1797) proposed that rocks,
    mountains, and valleys have been changed by
    water, wind, temperature, volcanoes, and other
    natural forces
  • He described the slow processes that shape Earth
    as gradualism

7
History of Evolutionary Theories
  • Charles Lyell (1797-1875) agreed with Hutton
    and said that scientists must always explain past
    events in terms of observable, PRESENT events and
    processes (uniformitarianism what happens
    today happened yesterday)
  • They theorized Earth was much older than a
    few thousand (6,000) years, which didnt
    set well in the traditional
    timeframe of Creationism

8
Age of the Earth
  • We now know Earth is approximately 4.5 billion
    years old
  • Darwin used the work of Hutton and Lyell as a
    basis for his theories of slow change over time.
    Darwins work was a biological duplicate of
    Hutton and Lyells works in geology.

9
Geologists study Earths rocks
  • Fossils are preserved remains of ancient
    organisms
  • As fossils are found that dont resemble
    organisms today, evidence increases that Earth
    has changed and that organisms have changed with
    it
  • Biologists and geologists date Earths past with
    the help of rocks

10
Geological Time Scale
  • RELATIVE DATING
  • Technique used to determine age of fossils
    relative to other fossils in different strata
  • This technique is VERY approximate

11
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12
Geological Time Scale
  • ABSOLUTE (RADIOMETRIC) DATING
  • Using radioactive elements in rock that decay at
    a steady rate to determine age
  • Decay measured in terms of HALF-LIFE
  • Half-life time required for half the
    radioactive atoms in a sample to decay

13
Radioactive Decay
  • During radioactive decay, the atoms of one
    element break down to form something else

Lose a proton
6 protons 4 neutrons
5 protons 4 neutrons
14
  • Rocks contain radioactive elements, each having a
    different half-life
  • EXAMPLES
  • Uranium-238 ? Lead-206 HL 4.5 B yrs
  • Potassium-40 ? Argon-40 HL 1.3 B yrs
  • Carbon-14 ? Nitrogen-14 HL 5770 yrs

15
  • Scientists often date rocks using Potassium-40,
    which decays to form the stable element Argon-40
  • It has a half life of 1.3 billion years
  • This is used to date the oldest rocks on earth

Formed
1.3 B yrs
2.6 B yrs
16
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17
  • Uranium and Potassium are useful for dating rocks
  • Carbon-14 is useful for dating things that were
    once alive such as wood, natural fiber, or cloth
  • C-14 is in the atmosphere living things take it
    in their cells. After the organism dies, it
    doesnt take in any more C-14. We can then
    compare the amounts of C-14 to N-14, knowing its
    half-life, to determine the age of the sample

18
Fossil Evidence
  • Found in Sedimentary rock layers of sand,
    silt, and clay in streams, lakes, rivers, and
    seas form rock that may have trapped living
    organisms
  • Fossil records Show change over time. Some
    time frames are missing, but will show change of
    climate and geography.
  • Ex Shark teeth in Utah
  • How can this be?

19
Jean Baptiste de Lamarck (1744-1829)
  • He also recognized that organisms were adapted to
    their environments and that they change
  • He relied on three ideas
  • A desire to change (innate drive for perfection)
  • Use and disuse (Giraffes necks and vestigial
    organs)
  • Inheritance of acquired characteristics

20
Darwins Dilemma
  • Set sail around the world in 1831 on HMS Beagle
    on a 5 year voyage
  • He had prior knowledge of geology (Lyell was a
    good friend) and agriculture that helped
    influence the development of his theory
  • Anchored all along the way and took samples
    from each place

21
Darwins Dilemma
  • He collected and studied beetles from Brazil,
    birds from Chile, and iguanas, tortoises, and
    finches from the Galápagos Islands
  • He noticed similarities between mainland
    (Ecuador) and Galapagos finches
  • Later, he noticed differences in beak size among
    finches from different islands in the Galapagos

22
Darwins Dilemma
  • Thomas Malthus wrote paper on population growth
    in Great Britain
  • Population grows exponentially
  • Limiting factors on growth (carrying capacity)
  • Food
  • Area
  • Resources

23
Darwins Dilemma
  • Darwin applied Malthus, Huttons, and Lyells
    work to species ability to change, and called
    the mechanism Natural Selection
  • Nat.Sel. Process by which organisms with
    favorable variations survive and produce more
    offspring than less well-adapted organisms
  • He was sure Nat.Sel. was true, but he
    feared public ridicule. So, he kept his
    ideas to himself

24
Darwins Dilemma
  • Alfred Russel Wallace (1823-1913), working
    independently, came to the same conclusions as
    Darwin
  • He sent a manuscript to Darwin, basically for
    proofreading
  • I never saw a more striking coincidence so all
    my originality, whatever it may amount to, will
    be smashed. Charles Darwin
  • Letter to Charles Lyell, June 18, 1858
  • Darwin quickly abridged and published his work
    On the Origin of Species

25
Darwins Natural Selection
  • Ernst Mayr, an evolutionary biologist, has
    dissected the logic of Darwins theory into three
    inferences based on five observations (Pg. 435)
  • Observations
  • Tremendous fecundity
  • Stable populations sizes
  • Limited environmental resources
  • Variation among individuals
  • Heritability of some of this variation.

26
Darwins Natural Selection
  • Observation 1 All species have such great
    potential fertility that their population size
    would increase exponentially if all individuals
    that are born reproduced successfully.

27
Darwins Natural Selection
  • Observation 2 Populations tend to remain stable
    in size,except for seasonal fluctuations.
  • Observation 3 Environmental resources are
    limited.

28
Darwins Natural Selection
  • Inference 1 Production of more individuals than
    the environment can support leads to a struggle
    for existence among the individuals of a
    population, with only a fraction of the offspring
    surviving each generation.

29
Darwins Natural Selection
  • Observation 4 Individuals of a population vary
    extensively in their characteristics no two
    individuals are exactly alike.
  • Observation 5 Much of this variation is
    heritable.

30
Darwins Natural Selection
  • Inference 2 Survival in the struggle for
    existence is not random, but depends in part on
    the hereditary constitution of the individuals.
  • Those individuals whose inherited characteristics
    best fit them to their environment are likely to
    leave more offspring than less fit individuals.

31
Darwins Natural Selection
  • Inference 3 This unequal ability of
    individuals to survive and reproduce will lead to
    a gradual change in a population, with favorable
    characteristics accumulating over the generations.

32
Evidence in Living Organisms
  • Comparative embryology
  • All vertebrate embryos look similar to one
    another in early development, with the
    development of a tail and gill arches
  • Ernst Haeckel made early drawings later exposed
    as frauds.
  • Gave fuel to anti-evolutionists

33
Evidence in Living Organisms
  • Comparative embryology
  • These anatomical similarities indicate similar
    genetics are at work
  • Become more dissimilar as they grow
  • Cell specialization and differentiation
  • Common ancestor?

34
Evidence in Living Organisms
35
Evidence in Living Organisms
  • Comparative anatomy
  • Homologous Structures
  • Analogous Structures
  • Vestigial Organs

36
Evidence in Living Organisms
  • Homologous Structures structures that are
    similar in anatomy, but may serve very different
    functions
  • Ex cat, whale, and human forearm

37
Homologous Structures
Flying
Swimming
Running
Grasping
38
Evidence in Living Organisms
  • Analogous Structures structures that serve
    similar functions, but have evolved independently
    of each other

39
Not homologous analogous
Not homologous not analogous
Homologous not analogous
Homologous analogous
40
Evidence in Living Organisms.
  • Vestigial organs organs that have little or no
    purpose in the organism may become smaller or
    even disappear
  • Ex Tailbone or appendix in humans
  • Ex Tiny leg bones in snakes (boas and
    pythons) thought to come from 4
    legged ancestor

41
Evidence in Living Organisms
  • Comparative biochemistry and molecular biology
  • All cells have DNA, RNA, ribosomes, the same 20
    amino acids and use ATP to do work
  • Similarities in biochemistry indicate relationship

42
Evidence in Living Organisms
  • Cytochrome c is a highly conserved respiratory
    protein containing 104 amino acids in humans

43
Evidence in Living Organisms
  • Amino acid differences of hemoglobin between
    species

44
What Homologies tell us
  • Similarities in structure and chemistry provide
    powerful evidence that all living things evolved
    from a common ancestor
  • Darwin Concluded
  • Living organisms evolved through gradual
    modifications of earlier forms ? descent with
    modification

45
What Similarities tell us
  • Two types of evolution can account for homologous
    AND analogous structures
  • Convergent evolution
  • Divergent evolution

46
What Similarities tell us
  • Divergent evolution two species evolve from a
    common ancestor (speciation)
  • They share similarities in anatomy, biochemistry,
    and embryology due to common ancestry
  • Explains homologous structures

47
What Similarities tell us
  • Convergent two species apparently becoming more
    similar
  • Two species have adapted in similar ways to
    similar environmental conditions
  • NOT due to common ancestry
  • Explains analogous structures

48
Convergent Evolution
  • Ocotillo from California and allauidi from
    Madagascar have evolved similar mechanisms for
    protecting themselves

49
Convergent Evolution
  • Adaptive radiation of anoles has occurred on the
    islands of the Greater Antilles in a convergent
    fashion. On each island, different species of
    the lizards have adapted to living in different
    parts of trees, in strikingly similar ways.

50
Convergent Evolution
51
Convergent Evolution
52
Diversity of Life
  • Fitness
  • Physical traits and behaviors that enable
    organisms to survive and reproduce in their
    environment arises from adaptation.
  • Adaptation allows species to be better suited to
    their environment and therefore can survive and
    reproduce.

53
Evolution on Different Scales
  • Microevolution generation-to-generation change
    in a populations allele frequencies
  • Macroevolution origin of new taxonomic groups
    speciation

54
4 Driving Forces behind Evol.
  • Mutation
  • Any change in the original DNA
  • ONLY ultimate source of variation in a population
  • Gene Flow
  • Movement of genes either into or out of a
    population
  • Migration Immigration (add alleles) and
    Emigration (subtract alleles)

55
4 Driving Forces behind Evol.
  • Genetic Drift
  • Change in the allele frequency in a small
    population by chance alone
  • Bottleneck Effect
  • Founder Effect

56
4 Driving Forces behind Evol.
  • Genetic Drift
  • Bottleneck Effect population undergoes a high
    mortality rate genetic variation decreases
    dramatically
  • Ex Cheetahs

57
Genetic Drift Bottleneck Effect
58
4 Driving Forces behind Evol.
  • Genetic Drift
  • Founder Effect few individuals leave a large
    population to start their own gene pool is very
    limited
  • Ex polydactyly in PA Amish

59
Genetic Drift Founder Effect
60
Genetic Drift Founder Effect
61
4 Driving Forces behind Evol.
  • Selection
  • Natural differential success in the
    reproduction of different phenotypes resulting
    from the interaction of organisms with their
    environment
  • Nature does the selecting

62
4 Driving Forces behind Evol.
  • Selection (Natural)
  • Resistance overuse of insecticides and
    antibiotics have bred resistant species of bugs
    and germs

63
4 Driving Forces behind Evol.
  • Selection
  • Artificial breeding of domesticated plants and
    animals
  • Humans intentionally do the selecting
  • Cabbage, cauliflower, Brussels sprouts,
    kale, kohlrabi and broccoli have a
    common ancestor in one species of wild
    mustard

64
4 Driving Forces behind Evol.
  • Problems with artificial selection not enough
    genetic variation

65
4 Driving Forces behind Evol.
  • Selection (Sexual)
  • Intrasexual selection selection within the same
    sex (competition, usually between males
  • Competition, usually between males
  • Exaggerated anatomy

Bighorn Sheep
Rocky Mountain Elk
Five-horned Rhinoceros Beetles
Stagbeetles
66
4 Driving Forces behind Evol.
  • Selection (Sexual)
  • Intersexual selection one sex selects mate
    based on phenotypes
  • Exaggerated anatomy

67
  • Selection can influence populations in three
    major ways
  • Directional Sel.
  • Stabilizing Sel.
  • Disruptive (diversifying) Sel.

68
Directional Selection
  • Environment selects against one phenotypic
    extreme, allowing the other to become more
    prevalent

69
Disruptive Selection
  • Environment selects against intermediate
    phenotype, allowing both extremes to become more
    prevalent

70
Stabilizing Selection
  • Environment selects against two extreme
    phenotypes, allowing the intermediates to become
    more prevalent

71
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72
Key Points
  1. Natural selection does not cause genetic changes
    in individuals.
  2. Natural selection acts on individuals evolution
    occurs in populations.
  3. Evolution is a change in the allele frequencies
    of a population, owing to unequal success at
    reproduction among organisms bearing different
    alleles.
  4. Evolutionary changes are not good nor
    progressive in any absolute sense.

73
Evolutionary Theory
  • Foundation on which the rest of the biological
    science is built. Collection of carefully
    reasoned and tested hypotheses about how
    evolutionary change occurs.

74
Speciation
  • What is a species?
  • Biological definition a group of closely related
    organisms (population) that can interbreed to
    produce fertile, viable offspring

75
Speciation
  • Why cant/dont populations interbreed?
  • Prezygotic barriers
  • Postzygotic barriers

76
Prezygotic Barriers
  • Ecological (habitat) isolation pops live in
    different habitats and do not meet
  • Parasites generally dont transfer hosts
  • Temporal isolation active or fertile at
    different times
  • Flowering plants pollinate on different days or
    different times of the day

77
Prezygotic Barriers
  • Behavioral isolation differences in activities
  • Mating calls or actions are different

78
Prezygotic Barriers
  • Mechanical isolation mating organs do not fit
    or match
  • Enough said
  • Gametic isolation gametes cannot combine
  • Sperm destroyed in different vaginal cavity
  • Sperm and egg dont fuse due to different
    membrane proteins

79
Postzygotic Barriers
  • Hybrid inviability hybrid zygotes fail to
    develop or reach sexual maturity
  • Hybrid infertility hybrids fail to produce
    functional gametes

80
Summary
  • 2 or more mechanisms may occur at once
  • Ex Bufo americanus and Bufo fowleri are
    ecologically, temporally, and behaviorally
    isolated
  • Bufo americanus breeds in early spring in small,
    shallow puddles or nearby dry creeks
  • Bufo fowleri breeds in late spring in large pools
    and streams
  • Their mating calls also differ

81
Limitations of Biological Species Concept
  • How do you classify organisms that
  • have the potential to interbreed, but do not do
    so in nature?
  • do not reproduce sexually?
  • exist only as fossils?
  • Alternative species concepts (ecological,
    pluralistic, morphological, genealogical) help
    address limitations

82
Modes of Speciation
  • Allopatric (Greek, allos other Latin, patria
    homeland)
  • Speciation due to geographic separation
  • Barrier stops gene flow between populations
  • Evolutionary change acts independently on each
    pop to establish reproductive barriers

83
  • Mitochondrial DNA analysis has shown that certain
    tamarin monkey pops (those separated by wide
    rivers) are diverging toward speciation
  • Where the Amazon is very wide, tamarins on one
    side are brown, but on the other side are white.
    Where the Amazon is narrow, tamarins of both
    colors are found on either side

84
Allopatric Speciation
  • Birds can move freely across the gorge of the
    Grand Canyon squirrels cannot
  • Two species arose when their original pop was
    disrupted by the carving of the canyon

85
  • A. harrisi
  • A. leucurus

86
Allopatric Speciation
  • If not given enough time, speciation will not
    occur
  • Also, even if they do
    come back together, they
    need to interbreed to be the same
    species

87
Allopatric Speciation
  • Figure 24.11
  • Adaptive Radiation evolution of
    many diversely-adapted species from a
    common ancestor
  • Ex Hawaiian archipelago

88
Sympatric Speciation
  • Sympatric (Greek, sym together Latin, patria
    homeland)
  • Speciation occurs in populations that share a
    habitat
  • Results from
  • Ecological isolation
  • Polyploidy (number of sets of chromosomes
    increases)

89
Sympatric Speciation
  • Polyploidy (number of sets of chromosomes
    increases)
  • A result of accidents in meiosis

90
Will Speciation Occur?
  • p q 1
  • p2 2pq q2 1
  • Will speciation occur? You tell me!
  • Hardy-Weinberg PPT 1
  • Hardy-Weinberg PPT 2

91
Evolutionary Time Scales
  • Evolution can take a long time or can occur
    relatively quickly
  • Gradualism
  • Punctuated Equilibrium

92
Evolutionary Time Scales
  • Gradualism big evolutionary changes are the
    result of many small ones over a long period of
    time

93
Evolutionary Time Scales
  • Punctuated Equilibrium speciation occurs fairly
    rapidly then remain constant

94
Evolutionary Novelties
  • Unique and highly specialized organs seem to
    complicated to have been naturally selected
  • Ex eyes are really just photoreceptors some are
    more developed, but all do the basic function
    receive light

95
Evolutionary Novelties
96
Evo-devo
  • Evolutionary development
  • A field of interdisciplinary research that
    examines how slight genetic divergences can
    become magnified into major morphological
    differences between species

97
Evo-devo
  • By blocking expression of one gene, researchers
    forced a chickens foot to develop to resemble a
    ducks foot
  • Two embryos from the same animal

98
Evo-devo
  • Left, a normal chicken leg will develop
  • Right, a normal duck leg will develop from a
    chicken embryo
  • Chicken leg scaled with 4 digits
  • Duck leg smooth and webbed
  • Duck legs, due to one genetic evolutionary
    difference, help ducks do many things chickens
    cannot, like swim
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