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Evolution
• Genetic change in a lineage over time
• first convincing case put forth by
– Charles Darwin
Artificial Selection in Agriculture
Artificial Selection
Agriculture
Corn looks very different from its ancestor
Artificial Selection
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Fig. 21.5-1
SCIENTIFIC THINKING
Question:
change?
Can artificial selection lead to substantial evolutionary
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
SCIENTIFIC THINKING
Question:
Can artificial selection lead to substantial evolutionary
change?
Hypothesis: Strong directional selection will quickly lead to a large
shift in the mean value of the population.
Experiment: In one population, every generation pick out the 20% of
the population with the most bristles and allow them to reproduce to
form the next generation. In the other population, do the same with
the 20% with the fewest number of bristles.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
SCIENTIFIC THINKING
Question:
Can artificial selection lead to substantial evolutionary
change?
Hypothesis: Strong directional selection will quickly lead to a large
shift in the mean value of the population.
Experiment: In one population, every generation pick out the 20% of
the population with the most bristles and allow them to reproduce to
form the next generation. In the other population, do the same with
the 20% with the fewest number of bristles.
Initial
population
Number of Individuals
Low
population
0
10
20
30
40
Mean
Mean
Mean
High
population
50
60
70
80
90
100
110
Bristle number in Drosophila
Result: After 35 generations, mean number of bristles has changed
substantially in both populations.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
SCIENTIFIC THINKING
Question:
Can artificial selection lead to substantial evolutionary
change?
Hypothesis: Strong directional selection will quickly lead to a large
shift in the mean value of the population.
Experiment: In one population, every generation pick out the 20% of
the population with the most bristles and allow them to reproduce to
form the next generation. In the other population, do the same with
the 20% with the fewest number of bristles.
Initial
population
Number of Individuals
Low
population
0
10
20
30
40
Mean
Mean
Mean
High
population
50
60
70
80
90
100
110
Bristle number in Drosophila
Result: After 35 generations, mean number of bristles has changed
substantially in both populations.
Interpretation: Note that at the end of the experiment, the range of
variation lies outside the range seen in the initial population.
Selection can move a population beyond its original range because
mutation and recombination continuously introduce new variation
into populations.
Evidence of Natural Selection
Darwin’s finches
Evidence of Natural Selection
Peter and Rosemary Grant studied medium ground finch
Natural Selection
Figure 21.4
Selection against melanism.The red circles indicate the frequency of
melanic Biston betularia moths at Caldy Common in Great Britain.
Green diamonds indicate frequencies of melanic B. betularia in
Michigan, and the blue squares indicate corresponding frequencies in
Pennsylvania.
Fig. 22.12
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• For patients treated with the drug 3TC, which interferes with
genome replication in HIV, 3TC-resistant strains become 100%
of the population of HIV in just a few weeks.
Fig. 22.13
Evolution of Super bugs: MRSA, or methicillin-resistant Staphylococcus aureus.
Multi-drug resistant tuberculosis; Clostridium difficile, etc
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fossil Evidence of Evolution
Whale “missing links”
Anatomical Evidence for
Evolution
• Vestigial
structures: have
no apparent
function, but
resemble structures
their ancestors
possessed
Vestigial structures of a
whale
Anatomical Evidence for
Evolution
• Humans
– Muscles for wiggling ears
• Boa constrictors
– Hip bones and rudimentary hind legs
• Manatees
– Fingernails on their fins
• Blind cave fish
– Nonfunctional eyes
Anatomical Evidence for
Evolution
Homology of the bones of the forelimb of
mammals
Anatomical Evidence for
Evolution
Convergent evolution of fast swimming predators
Anatomical Evidence for
Evolution
Developmental similarities reflect descent
from a common ancestor
Evolution
• A unifying theme in Biology
• Explains the diversity and unity we observe
Charles
Darwin
• Naturalist on
HMS Beagle in 1831
• Galapagos Islands
• the origin of new
species
Origin of Species, 1859
• Two main points
– 1. Evolution explains the unity and diversity of
life
• “descent with modification”
– 2. Natural selection was the main cause of
evolution
• differential reproductive success leads to adaptation
Evolution
• Individuals do not evolve
• Populations are the smallest units that can
evolve
– a group of interbreeding individuals belonging
to a particular species sharing a common
geographic area
• Discussed “microevolution” in BIO 150
Origin of New Species
• Biological species concept
– a population or group whose members have the
potential to interbreed with one another in
nature to produce viable, fertile offspring, but
who cannot successfully interbreed with other
such groups
– does not work for everything
• asexual, extinct, geographically separated???
• Species are based on interfertility, not physical
similarity.
• For example, the eastern and western meadowlarks
may have similar shapes and coloration, but
differences in song help prevent interbreeding
between the two species.
• In contrast, humans have
considerable diversity,
but we all belong to the
same species because of
our capacity to interbreed.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 24.2
Speciation
• Evolution of reproductive barriers
– the key biological event in the origin of new
species
– any factor that impedes two species from
producing fertile hybrids, thus contributing to
reproductive isolation
– prezygotic and postzygotic
Tab. 22.1
Tab. 22.1.contd.
https://www.youtube.com/watch?v=z922by9_6Fw
Later found Prezygotic isolation- different songs
https://www.youtube.com/watch?v=kUdeEw2BPsQ
Types or Modes of Speciation
Fig 24.6
Types of Speciation
• Allopatric speciation
– speciation event in which the initial block to
gene flow is a geographic barrier that
physically isolates the populations
Reasons for Geographic Isolation
Example of Allopatric speciation
Fig 24.7
Periodic Isolation in Alpine Buttercup
snowfield
snowline fringe
stony debris
sheltered
boggy
a.
Glaciers
recede
Glaciers link alpine zones into one
continuous range.
Glaciation
Mountain populations become isolated,
permitting divergence and speciation.
Alpine zones are reconnected. Separately
evolved species come back into contact.
b.
a(1): © Photo New Zealand/Hedgehog House; a(2): © Jim Harding/First Light; a(3): © Colin Harris/Light Touch
Images/Alamy; a(4)-(5): © Focus New Zealand Photo Library.
Fig. 22.16
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• The key to allopatric speciation is whether the
separated populations have become different enough
that they can no longer interbreed and produce fertile
offspring when they come back in contact.
Fig. 24.8
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Types of Speciation
• Sympatric speciation
– formation of new species within the range of
the parental population
– Much less common
– Polyploidy
– Or disruptive selection
Polyploidy and Sympatric Speciation
What Causes Reproductive
Isolation to Evolve?
• Selection
– May cause the initial isolation if populations
are adapting to different environments
– May lead to reinforcement of isolating
mechanisms
• Random changes
Reinforcement in European Flycatchers
Pied
flycatcher
Pied
flycatcher
Collared
flycatcher
Collared
flycatcher
Macroevolution
• Origin of taxonomic groups higher than the
species level
• evolutionary change substantial enough to
view its products as new genera, families or
phyla
• Has a random component
Macroevolution
• The study of
– major evolutionary innovations
• bird feathers, insect wings
Macroevolution
• The study of
– evolutionary trends
Fig. 21.13
Oligocene
30MYA
45MYA
50MYA
55MYA
60MYA
Hyracotherium
(browsers)
Orohippus
Eocene
Hyracotherium
40MYA
Epihippus
35MYA
Mesohippus
(browsers)
Mesohippus
Anchitherium
(browsers)
Merychippus
(mixed feeders)
Neohipparion
(grazers)
Nannippus
(grazers)
Equus
(grazers)
Equus
Dinohippus
Onohippidion
Astrohippus
Pliohippus
Calippus
Protohippus
Cormohipparion
Nannippus
Merychippus
Parahippus
Desmatippus
25MYA
Miohippus
20MYA
Archaeohippus
15MYA
Kalobatippus
Miocene
Anchitherium
10MYA
Hypohippus
5MYA
Hipparion
browsers
grazers
mixed feeders
Megahippus
Pliocene
Neohipparion
Pleistocene
Pseudhipparion
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Macroevolution
• The study of
– trends in biodiversity
• extinctions and radiations
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
0
Fig. 22.18
Cretaceous
100
200
Triassic
Millions of years ago
Permian
300
Devonian
400
Ordovician
500
600
0
200
400
600
Number of families
800
1000
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Millions of
years ago
First hominids
100
Extinction of
the dinosaurs
200
Flowering plants
and first birds
Mammals and dinosaurs
300
Reptiles
Insects and amphibians
400
Colonization of
land by animals
500
600
Fig. 21.10
Vertebrates
Plants
Diversification of multicellular
life and algae
2200
2700
Oldest eukaryotes
Oxygen increases
in the atmosphere
3500
3800
Oldest fossils
First signs of life
4600
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Ground and Cactus Finches
Geospiza
fuliginosa
Geospiza
fortis
Geospiza
magnirostris
Fig. 22.14
Camarhynchus
parvulus
Geospiza
conirostris
Geospiza
scandens
Vegetarian
Tree Finch
Tree Finches
Geospiza
difficilis
Camarhynchus
pauper
Camarhynchus
psittacula
Cactospiza
pallida
Cactospiza
heliobates
Warbler
Finches
Certhidea
fusca
Platyspiza
crassirostris
Certhidea
olivacea
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Fig. 22.15
Scale scraper
Leaf eater
Snail eater
Fish eater
Second
set of jaws
Zooplankton eater
Algae scraper
Insect eater
Macroevolution
• The study of
– pace of evolution
Time
Pace of Evolution
Fig. 22.17
a. Gradualism
b. Punctuated equilibrium
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Macroevolution
• Fossil record provides the outline of
macroevolution
• must also study extant species to provide
the details