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Unit 4 Review
Mechanisms of Evolution
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 22Chapter 22
Descent with Modification: A Darwinian View of Life
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Darwin worked in a historical CONTEXT!
• Others’ ideas shaped Darwin’s thinking…
Figure 22.2
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)
Wallace (evolution, natural selection)
1750
American Revolution French Revolution U.S. Civil War
1800 1850 19001795 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.
Darwin begins his notebooks on the origin of species.1837Darwin writes his essay on the origin of species.1844
Wallace sends his theory to Darwin.1858
The Origin of Species is published.1859Mendel publishes inheritance papers.1865
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Figure 22.10
Terminalbud
Lateralbuds
Brussels sproutsCabbage
Flowercluster
Leaves
Cauliflower
Flowerandstems
Broccoli Wild mustard Kohlrabi
Stem
Kale
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• 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
Figure 22.14Human Cat Whale Bat
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• Comparative embryology
– Reveals additional anatomical homologies not visible in adult organisms
Figure 22.15
Pharyngealpouches
Post-analtail
Chick embryo Human embryo
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Vestigial organs:
– remnants of structures that served important functions in the organism’s ancestors
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Biochemical Comparisions:
• Particularly comparison of:
– DNA
– Proteins
Figure 22.16
Species
Human
Rhesus monkey
Mouse
Chicken
Frog
Lamprey14%
54%
69%
87%
95%
100%
Percent of Amino Acids That AreIdentical to the Amino Acids in aHuman Hemoglobin Polypeptide
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 22.18
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 23Chapter 23
The Evolution of Populations
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Five (rarely met) conditions for non-evolving populations…
– Extremely large population size
– No gene flow
– No mutations
– Random mating
– No natural selection
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 24Chapter 24
The Origin of Species
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Limitations of the Biological Species Concept
• The biological species concept cannot be applied to…?
– Asexual organisms
– Fossils
– Organisms with unknown reproductive cycles
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Prezygotic barriers … continued next slide…
Figure 24.4
Individualsof differentspecies
Matingattempt
Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
HABITAT ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION
(b)
(a)(c)
(d)
(e)
(f)
(g)
. . . . . . .
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Viablefertile
offspring
Reducehybrid
viability
Reducehybridfertility
Hybridbreakdown
Fertilization
Gameticisolation
GAMETIC ISOLATION REDUCED HYBRID VIABILITY
REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
(h) (i)
(j)
(k)
(l)
(m)
• ………………postzygotic barriers.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
(a) Allopatric speciation. A population forms a new species while geographically isolated from its parent population.
(b) Sympatric speciation. A smallpopulation becomes a new specieswithout geographic separation.
• Speciation can occur in two ways
– Allopatric speciation
– Sympatric speciation
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A. harrisi A. leucurus
• Allopatric or Sympatric?
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Adaptive Radiation?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings? ?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Evolutionary Novelties
• Most novel biological structures
– Evolve in many stages from previously existing structures
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Hox Genes??
• Associated with the evolution of vertebrates
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Most Species are?• Dead Ends!
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 25Chapter 25
Phylogeny and Systematics
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Linking Classification and Phylogeny
• Systematists depict evolutionary relationships in phylogenetic trees (cladograms)
Figure 25.9
Panthera pardus
(leopard)
Mephitis mephitis
(striped skunk)
Lutra lutra (European
otter)
Canis familiaris
(domestic dog)
Canislupus (wolf)
Panthera Mephitis Lutra Canis
Felidae Mustelidae Canidae
Carnivora
Ord
erF
amily
Gen
us
Sp
ecie
s
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• “Deeper” branch points represent…
– progressively greater amounts of divergence
– longer times since divergence
Leopard Domestic cat
Common ancestor
Wolf
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Monophyletic? Paraphyletic?
• A valid clade is monophyletic
– Signifying that it consists of the ancestor species and all its descendants
Figure 25.10a
Grouping 1
D
C
E G
F
B
A
J
I
KH
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Outgroup? Derived Character? Cladogram?
• Cladograms help determine who branched off when.
• Presence or absence of derived characters determines how you build the cladogram.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Universal Tree of Life
• The tree of life is divided into three great clades called domains: Bacteria, Archaea, and Eukarya
• The early history of these domains is complex
Figure 25.18
Bacteria Eukarya Archaea4 Symbiosis of
chloroplast ancestor with ancestor of green plants
3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes
2 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells
1 Last common ancestor of all living things
4
3
2
1
1
2
3
4
0
Bill
ion
ye
ars
ag
o
Origin of life
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