Evolution, Darwin and Evidence

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Evolution, Darwin and Evidence

• Descent with Modification A
  Darwinian View of Life

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Evolution

• Evolution the change over time of the
  genetic composition of populations
• Natural selection populations of organisms can
  change over the generations if individuals having
  certain heritable traits leave more offspring
  than others (differential reproductive success)
• Evolutionary adaptations a prevalence of
  inherited characteristics that enhance organisms
  survival and reproduction

November 24, 1859
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Evolutionary history

• Linnaeus taxonomy
• Hutton gradualism
• Lamarck evolution
• Malthus populations
• Cuvier paleontology

• Lyell uniformitarianism
• Darwin evolution
• Mendel inheritance
• Wallace evolution

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Charles Darwin

• 1809-1882
• British naturalist
• Proposed the idea of evolution by natural
  selection
• Collected clear evidence to support his ideas

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Voyage of the HMS Beagle

• Invited to travel around the world
• 1831-1836 (22 years old!)
• makes many observations of nature
• main mission of the Beagle was to chart South
  American coastline

Stopped in Galapagos Islands 500 miles off coast
of Ecuador
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Darwin found birds

• Collected many different birds on the Galapagos
  Islands.

Finch?
Sparrow?
Thought he found very different kinds
Warbler?
Woodpecker?
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But Darwin found a lot of finches

• Darwin was amazed to find out
• All 14 species of birds were finches

But there is only one species of finch on the
mainland!
Large Ground Finch
Small Ground Finch
Sparrow?
How didone species of finches becomeso many
differentspecies now?
Warbler Finch
Veg. Tree Finch
Warbler?
Woodpecker?
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Darwins finches

• Differences in beaks
• associated with eating different foods
• survival reproduction of beneficial adaptations
  to foods available on islands

Warbler finch
Cactus finch
Woodpecker finch
Sharp-beaked finch
Small insectivorous tree finch
Small ground finch
Warbler finch
Large insectivorous tree finch
Cactus eater
Mediumground finch
Tree finches
Ground finches
Insect eaters
Seed eaters
Vegetarian tree finch
Large ground finch
Bud eater
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Darwins finches

• Darwins conclusions
• small populations of original South American
  finches landed on islands
• variation in beaks enabled individuals to gather
  food successfully in the different environments
• over many generations, the populations of finches
  changed anatomically behaviorally
• accumulation of advantageous traits in population
• emergence of different species

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Seeing this gradation diversity of structure
in one small, intimately related group of birds,
one might really fancy that from an original
paucity of birds in this archipelago, one
species has been taken modified for different
ends.
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Darwins finches

• Differences in beaks allowed some finches to
• successfully compete
• successfully feed
• successfully reproduce
• pass successful traits onto their offspring

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Correlation of species to food source
More observations
Whoa,Turtles, too!
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Essence of Darwins ideas

• Natural selection
• variation exists in populations
• over-production of offspring
• more offspring than the environment can support
• competition
• for food, mates, nesting sites, escape predators
• differential survival
• successful traits adaptations
• differential reproduction
• adaptations become more common in population

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Evolution evidence Biogeography

• Geographical distribution of species
• Examples Islands vs. Mainland Australia Contin
  ents

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Evidence supporting evolution

• Fossil record
• transition species
• Anatomical record
• homologous vestigial structures
• embryology development
• Molecular record
• protein DNA sequence
• Artificial selection
• human-caused evolution

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Fossil record

• Layers of sedimentary rock contain fossils
• new layers cover older ones, creating a record
  over time
• fossils within layers show that a succession of
  organisms have populated Earth throughout a long
  period of time

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Evolution evidence The Fossil Record

• Succession of forms over time
• Transitional links
• Vertebrate descent

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Fossil record

• A record showing us that todays organisms
  descended from ancestral species

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Evolutionary change in horses
550
500
450
Equus
400
350
Body size (kg)
300
250
Merychippus
200
Mesohippus
150
Hyracotherium
100
50
Nannippus
60
55
50
45
40
35
30
25
20
15
10
5
0
Millions of years ago
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Evolution of birds

• Archaeopteryx
• lived about 150 mya
• links reptiles birds

Smithsonian Museum, Washington, DC
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Evolution evidence Comparative Anatomy

• Homologous structures (homology)
• Descent from a common ancestor

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Homologous structures

• Similar structure
• Similar development
• Different functions
• Evidence of close evolutionary relationship
• recent common ancestor

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Analogous structures

• Separate evolution of structures
• similar functions
• similar external form
• different internal structure development
• different origin
• no evolutionary relationship

Dont be fooledby their looks!
Solving a similar problem with a similar solution
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Vestigial organs

• Modern animals may have structures that serve
  little or no function
• remnants of structures that were functional in
  ancestral species
• deleterious mutations accumulate in genes for
  non-critical structures without reducing fitness
• snakes whales remains of pelvis leg bones
  of walking ancestors
• eyes on blind cave fish
• human tail bone

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Vestigial organs

• Hind leg bones on whale fossils

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Evolution evidence Comparative Embryology

• Pharyngeal pouches, tails as embryos

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Evolution evidence Molecular Biology

• Similarities in DNA, proteins, genes, and gene
  products
• Common genetic code

• Closely related species have sequences that are
  more similar than distantly related species
• DNA proteins are a molecular record of
  evolutionary relationships

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Comparative hemoglobin structure
Dog
Lamprey
Frog
Bird
Macaque
Human
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8
45
125
67
10
0
20
30
40
50
60
70
80
90
100
110
120
Number of amino acid differences
between hemoglobin (146 aa) of vertebrate species
and that of humans
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Building family trees

• Closely related species (branches) share same
  line of descent until their divergence from a
  common ancestor

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Artificial selection

• Artificial breeding can use variations in
  populations to create vastly different breeds
  varieties

descendants of the wolf
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Natural selection in action

• Insecticide drug resistance
• insecticide didnt kill all individuals
• resistant survivors reproduce
• resistance is inherited
• insecticide becomes less less effective

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Final words...

• Absence of evidence is not evidence of absence.