Download Unit 3 - ISD 622

Unit 4 Review
Mechanisms of Evolution
Chapter 22
Descent with Modification: A
Darwinian View of Life
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Darwin worked in a historical CONTEXT!
• Others’ ideas shaped Darwin’s thinking…
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, nutural selection)
Mendel (inheritance)
American Revolution
1750
Wallace (evolution, natural selection)
French Revolution
U.S. Civil War
1800
1850
1900
1795 Hutton proposes his theory of gradualism.
1798 Malthus publishes “Essay on the Principle of Population.”
1809 Lamarck publishes his theory of evolution.
1830 Lyell publishes Principles of Geology.
1831–1836 Darwin travels around the world on HMS Beagle.
1837 Darwin begins his notebooks on the origin of species.
1844 Darwin writes his essay on the origin of species.
1858 Wallace sends his theory to Darwin.
1859 The Origin of Species is published.
1865 Mendel publishes inheritance papers.
Figure 22.2
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• Elements of Darwin’s theory of…
Evolution by Natural Selection?
– organisms overproduce offspring
– members of a population differ in adaptations
– competition for limited resources
– survival of the fittest
– population changes over time
• What was Darwin missing?
– He couldn’t describe a mechanism for the
variation in adaptations. Can you?
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Artificial Selection
• Artificial selection: Humans have modified
other species by selecting and breeding
individuals that possess desired traits
Terminal
bud
Lateral
buds
Brussels sprouts
Cabbage
Flower
cluster
Leaves
Cauliflower
Kale
Flower
and
stems
Broccoli
Stem
Wild mustard
Figure 22.10
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Kohlrabi
• If an environment changes over time
– Natural selection may result in adaptation
• Does the individual or population evolve?
• The alternative to adapting?
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Caused by
the pesticide?
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Homologous structures:
– variations on a structural theme inherited from
a common ancestor
Human
Cat
Figure 22.14
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Whale
Bat
• Comparative embryology
– Reveals additional anatomical homologies not
visible in adult organisms
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Figure 22.15
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Human embryo
Vestigial organs:
– remnants of structures that served important
functions in the organism’s ancestors
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Biochemical Comparisions:
• Particularly
comparison of:
– DNA
– Proteins
Species
Percent of Amino Acids That Are
Identical to the Amino Acids in a
Human Hemoglobin Polypeptide
100%
Human
Rhesus monkey
95%
Mouse
87%
Chicken
69%
Frog
Figure 22.16
Lamprey
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54%
14%
• The Darwinian view of life
– Predicts that evolutionary transitions should
leave signs in the
• fossil record
• Paleontologists have
discovered fossils of
many such transitional
forms
Figure 22.18
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Chapter 23
The Evolution of Populations
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Modern Synthesis
• Population genetics…
– Merges & extends Darwin’s & Mendel’s ideas
– Focuses on populations as units of evolution
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The Hardy-Weinberg Theorem
• The Hardy-Weinberg theorem describes a
population that is not _________.
– evolving
– States that allele frequencies in a gene pool
will remain constant from generation to
generation, IF:
• only Mendelian segregation and
recombination of alleles are at work
• no evolutionary forces are at work
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• Five (rarely met) conditions for non-evolving
populations…
– Extremely large population size
– No gene flow
– No mutations
– Random mating
– No natural selection
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You reviewed these with the graphical Q’s, right?
Hardy-Weinberg Equations - If a population has only
two possible alleles at a particular locus, & one is
dominant, and no evolutionary forces are working:
• p + q = 1 (sum of allele frequencies = 1)
• p = frequency of the dominant allele in the population
• q = frequency of the recessive allele in the population
• p2 + 2pq + q2 = 1 (sum of genotype frequencies = 1)
• p2 = frequency of homozygous dominant individuals
• q2 = frequency of homozygous recessive individuals
• 2pq = frequency of heterozygous individuals
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• Two processes produce variation in gene pools.
What are they? Which one happens FIRST?
– 1st: Mutation creates allele variations.
– 2nd: Sexual recombination
generates new allele combinations via:
• crossing over during meiosis
• random segregation into gametes
• random recombination during fertilization
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• Three major factors alter allele frequencies and
bring about most evolutionary change
– Natural selection
– Genetic drift
– Gene flow
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Directional, Disruptive, and Stabilizing Selection
• Selection can only act on an individual’s …
– phenotype
• This allows damaging recessive alleles to hide
in ___________, and avoid elimination from
the gene pool.
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• The three modes of selection
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Why does complex sexual reproduction persist?
– It produces genetic variation that may aid in…
• disease resistance
• better predator evasion
• better feeding efficiency
• survival in a changing environment
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Why can’t evolution fashion perfect organisms?
– Mutations are RANDOM, not chosen
– Adaptations are often compromises
– Selection can only edit existing variations…
• gotta’ work with what we’ve got.
– “Perfect” is a moving target…
• Predators, prey & competitors keep
changing
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Chapter 24
The Origin of Species
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Speciation
– is where microevolution of populations gives
way to macroevolution
• Macroevolution
– Refers to evolutionary change that leads to
whole new clades of creatures
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Limitations of the Biological Species Concept
• The biological species concept cannot be
applied to…?
– Asexual organisms
– Fossils
– Organisms with unknown reproductive cycles
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• Prezygotic barriers …
Habitat
isolation
continued next slide…
Behavioral
isolation
Temporal
isolation
.......
Mating
Individuals
of different
species
HABITAT ISOLATION
Mechanical
isolation
attempt
TEMPORAL ISOLATION
BEHAVIORAL ISOLATION
MECHANICAL ISOLATION
(g)
(b)
(d)
(e)
(f)
(a)
(c)
Figure 24.4
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• ………………postzygotic barriers.
Gametic
isolation
Reduce
hybrid
fertility
Reduce
hybrid
viability
Hybrid
breakdown
Viable
fertile
offspring
Fertilization
REDUCED HYBRID
VIABILITY
GAMETIC ISOLATION
REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
(k)
(j)
(m)
(l)
(h)
(i)
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• Speciation can occur in two ways
– Allopatric speciation
– Sympatric speciation
(a)
Allopatric speciation. A
population forms a new
species while geographically
isolated from its parent
population.
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(b)
Sympatric speciation. A small
population becomes a new species
without geographic separation.
• Allopatric or Sympatric?
A. harrisi
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A. leucurus
Adaptive Radiation?
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?
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?
Evolutionary Novelties
• Most novel biological
structures
– Evolve in many
stages from
previously existing
structures
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Hox Genes??
• Associated with
the evolution of
vertebrates
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Most Species are?
• Dead Ends!
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Chapter 25
Phylogeny and Systematics
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Investigating the Tree of Life
• Phylogeny:
– The evolutionary history of a species or group
of related species
• Phylogenies are constructed from three major
types of evidence:
– fossil, morphological, and molecular
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Figure 25.9
Species
Panthera
pardus
(leopard)
Mephitis
mephitis
(striped skunk)
Lutra lutra
(European
otter)
Genus
Panthera
Mephitis
Lutra
Felidae
Order
• Systematists depict
evolutionary
relationships in
phylogenetic trees
(cladograms)
Family
Linking Classification and Phylogeny
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Mustelidae
Carnivora
Canis
familiaris
(domestic dog)
Canis
lupus
(wolf)
Canis
Canidae
• “Deeper” branch points represent…
– progressively greater amounts of divergence
– longer times since divergence
Wolf
Leopard
Common ancestor
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Domestic cat
Monophyletic? Paraphyletic?
• A valid clade is monophyletic
– Signifying that it consists of the ancestor
species and all its descendants
Grouping 1
E
D
J
H
G
F
C
I
B
A
Figure 25.10a
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K
Outgroup?
Derived Character?
Cladogram?
• Cladograms help determine who branched off
when.
• Presence or absence of derived characters
determines how you build the cladogram.
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Mutation rates vary for different types of genes.
• Which mutation pattern is best for comparing closely
related species? Distantly related species?
mtDNA genes
rRNA genes
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The Universal Tree of Life
• The tree of life is
• The early history of
these domains is
complex
Bacteria
Billion years ago
divided into three
great clades
called domains:
Bacteria,
Archaea, and
Eukarya
Eukarya Archaea
0
4 Symbiosis of
chloroplast
ancestor with
ancestor of green
plants
1
3 Symbiosis of
mitochondrial
ancestor with
ancestor of
eukaryotes
4
2
3
2 Possible fusion
of bacterium and
archaean,
yielding ancestor
of eukaryotic
cells
2
3
1
Origin of life
4
Figure 25.18
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1 Last common
ancestor of all
living things