Download Evolution

Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
LEC #17
Important Latin Roots
Homo
ology
• one
Common Ancestry
• Study of • Common = S haring
• form
• Latin antecessor predecessor
Natural Selection • Latin nātūrālis – from nature
• Selectus – to choose Evolution
• Latin from evolvere -­‐ unrolling, Evolution • Evolution = genetic change in a population over time • Evolution is BOTH 1. An observation (we see it happening t oday) 2. AND a theory (extensive evidence supports t he hypothesis t hat evolution doesn’t just happen t oday, it’s happened since life began) CHARLES DARWIN & THE ORIGIN OF SPECIES
– Biology came of age on November 2 4, 1 859. – Charles D arwin p ublished On the Origin o f Species b y Means o f Natural Selection, an assemblage of facts about the n atural world.
Darwin made three observations from these facts.
1
Life shows rich diversity.
2
There are similarities in life that allow the c lassification of organisms into groups nested within broader groups.
3
Organisms display m any striking ways in which they are suited for their environments.
(a) The diversity of life
© 2 0 1 3 P earso n Ed u catio n , In c.
Zannie Dallara (b) Patterns of similarities
(c) A n insect suited to
its environment
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Darwin
CHARLES DARWIN AND THE ORIGIN O F S PECIES
CHARLES DARWIN AND THE ORIGIN OF
SPECIES
– Darwin h ypothesized that
• Present-­‐day species are the descendants of ancient ancestors t hat they still resemble in some ways and
• Change occurs as a result of “ descent with modification,”
with natural selection as the mechanism.
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Historical context of Darwin’s ideas
• Common beliefs
– Who created living organisms?
– Did they evolve?
– What was the age of the earth?
– Did the earth change?
Darwin’s 5 Year Voyage
HMS Beagle
Dar win in 1840
Nor th
Am er ica
Galápagos
Islands
Eur ope
Asia
ATLANTIC
OCEAN
Afr ica
Pinta
PACIFIC
OCEAN
Ge nov e s a
Ma rc he na
Equa tor
Sa ntia go
Da phne Islands
Fe rna ndina Pinz ón
Is a be laSa nta
Sa nta
Cruz Fe
Sa n
Cris toba l
Flore nz a Es pa ñola
0
40 km
0
Gr eat Br itain
South
Am er ica
Equator
Austr alia
PACIFIC
OCEAN
Cape of Good Hope
Cape Hor n
40 m i l es
Tasm ania
New Zealand
Tier r a del Fuego
CHARLES DARWIN’S UNEXPECTED
PATTERNS
1. Divergence from original population
– Same species w/
different traits?
– 13 different sp.
–
Large ground finch
Warbler finch Woodpecker finch © 2 0 1 3 P earso n Ed u catio n , In c.
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
LEC #17
Biology and Society:
Mosquitoes, Microbes, and Malaria
• In the 1 960s, the World H ealth Organization (WHO) launched a campaign to eradicate the mosquitoes that transmit malaria.
• It u sed D DT, to which s ome mosquitoes have evolved resistance.
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Biology and Society:
Mosquitoes, Microbes, and Malaria
– The evolution of pesticide-­‐resistant insects is just one of the ways that evolution affects our lives.
DDT
– Survival of the fittest (luckiest) An understanding of evolution informs every field of biology, for example,
• Medicine,
• Agriculture,
• Biotechnology
• Conservation biology.
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CHARLES DARWIN AND THE ORIGIN OF
SPECIES
– Natural selection is a p rocess in which organisms with certain inherited characteristics are more likely to s urvive and reproduce than are individuals with other characteristics.
– Q: What was the character n atural selection a cted on in the rubber d ucky/mosquito example?
– As a result of n atural s election, a population, a group of individuals of the s ame s pecies living in the s ame place at the s ame time, changes over generations.
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
LEC #17
CHARLES DARWIN AND THE ORIGIN OF
SPECIES
– Natural s election leads to e volutionary adaptation, a population’s increase in the frequency of traits s uited to the environment.
– Natural s election thus leads to e volution, s een either as
• a change in t he genetic composition of a population over time or
• on a grander scale, t he entire biological history, from t he earliest microbes to t he enormous diversity of organisms t hat live on Earth today.
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Lamarkian Evolution • Pro: Saw Change over time
• Con: Thought it was about effort
–Use it or lose it
• Set the stage for Darwin
Descent with Modification
• Darwin made two main points in The Origin of S pecies.
1. Organisms inhabiting Earth today descended from ancestral s pecies. = Common ancestor 2. Natural s election is the mechanism for descent with modification.
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Evidence for Evolution Theory 1. Direct observation – we see it happening today 2. The fossil r ecord
3. Biogeography
4. Comparative anatomy 5. Comparative embryology 6. Molecular Biology Q: Why is studying fruit flies and bacteria beneficial for an evolutionary biologist?
The Fossil Record
Fossils are
• Imprints or remains of organisms that lived in the past • often found in sedimentary rocks.
• is the ordered sequence of fossils as they appear in rock layers,
• reveals t he appearance of organisms in a historical sequence
•
fits with the m olecular and c ellular evidence that prokaryotes are the ancestors of all life.
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Fi g u re 1 3 .6
Video: G rand Canyon The Fossil Record
– Paleontologists ( scientists who study fossils) have discovered many transitional forms that link p ast and present.
– Transitional fossils include evidence that
• birds descended from one branch of dinosaurs and
• whales descended from four-­‐legged land mammals.
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Biogeography
– Biogeography, the s tudy of the geographic d istribution of s pecies, first s uggested to D arwin that today’s organisms evolved from ancestral forms.
(Look like neighbors) – One example is the d istribution of marsupial mammals in Australia.
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Pangea
Why does the pronghorn run so fast?
The pronghorn is the fastest land mammal in the Western Hemisphere
55mph/.5mile
Only beat by the cheetah
Comparative Anatomy
Comparative anatomy
• The comparison of body structure between different species
F ig u re 1 3 .9
– Attests that evolution is changes from an ancestral structure. Becoming modified as they take on n ew All Mammals functions.
• Homology is
– the similarity in structures due t o common ancestry and
– illustrated by t he remodeling of t he pattern of bones forming t he forelimbs of mammals for different Human
functions.
Cat
Whale
Bat
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
Human
Cat
Whale
LEC #17
Bat
What is a reasonable conclusion you can draw from this?
Comparative Anatomy
• Vestigial structures
– Are remnants of features that s erved important functions in an organism’s ancestors and
– Now h ave only marginal, if any, importance.
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Comparative Embryology
• Early stages of development are similar
• For example, pharyngeal pouches appear on t he side of t he embryo’s t hroat, w hich
• develop into gill structures in fish and
• form parts of the ear and throat in humans.
– Comparative embryology of vertebrates supports evolutionary theory.
Pharyngeal
pouches
Post-­‐anal
tail
Chicken embryo
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Zannie Dallara Human embryo
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Comparative Embryology
“ontogeny recapitulates phylogeny”
Who is most closely related?
A
B
C
D
E
Molecular Biology
– The hereditary background of an organism is documented in
• its D NA and
• the p roteins encoded b y the DNA.
– Evolutionary relationships among species can be determined by comparing
• genes and • proteins of d ifferent organisms.
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Summary from Textbook
11.2 Mechanisms of Evolution • There are four factors that can change the allele frequencies of a population. 1. Natural selection works by s electing for alleles that confer beneficial traits or behaviors, while selecting against those for d eleterious qualities. 2. Mutations introduce new alleles into a p opulation. 3. Genetic drift stems from the chance occurrence that some individuals have more offspring than others and results in changes in allele frequencies that are random in d irection. 4. When individuals leave or join the population, allele frequencies can change as a result of gene flow. Zannie Dallara 11
Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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How does evolution happen?
1. Natural Selection
2. Sexual Selection
3. Genetic Drift
4. Gene Flow
All of these r equire genetic diversity – so mutation is a r equirement for all evolution
Darwin’s Theory of Natural Selection
• Darwin based his theory of natural selection on two key observations.
1. All species tend to produce excessive numbers of offspring. = O VERPRODUCTION Overproduction 2. Organisms vary, and much of this variation is heritable.
Observations
Overproduction
of offspring
Individual
variation
Conclusion
Natural selection:
unequal reproductive success
Figure 1 3.UN3
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Darwin’s Theory of Natural Selection
– Observation 1: Overproduction and competition
• All s pecies h ave the p otential to p roduce many more offspring than the environment can s upport.
• This leads to inevitable competition among individuals.
Overproduction Overproduction Competition © 2 0 1 3 P earso n Ed u catio n , In c.
Darwin’s Theory of Natural Selection
– Observation 2 : Individual variation
• Variation exists among individuals in a population.
• Much of t his v ariation is heritable.
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Darwin’s Theory of Natural Selection
• Inference: Unequal reproductive success
(natural selection)
– Those individuals with traits b est s uited to the local environment generally leave a larger share of s urviving, fertile offspring.
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Natural Selection in Action
– Examples of n atural s election include
DDT
• pesticide-­‐resistant insects,
• antibiotic-­‐resistant bacteria, and
• drug-­‐resistant strains of HIV.
Fi g u re 1 3 .1 5 -­3
Insecticide application
Chromosome with gene
conferring resistance
to pesticide
Survivors
Reproduction
What defenses does this animal have?
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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The Process of Science: Does Predation Drive the
Evolution of Lizard Horn Length?
– Observation: Flat-­‐tailed h orned lizards d efend against attack b y
• thrusting t heir heads backward and
• stabbing a shrike with t he spiked horns on t he rear of t heir skull.
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The Process of Science: Does Predation Drive the
Evolution of Lizard Horn Length?
– Question: Are longer h orn length and s pread a survival advantage?
– Hypothesis: Longer h orn length and s pread are a survival advantage.
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blog.therainforestsite.com
The Process of Science: Does Predation Drive
the Evolution of Lizard Horn Length?
– Prediction: Live h orned lizards h ave longer and more widely spread h orns than d ead ones.
– Experiment: M easure the h orn lengths and the tip-­‐
to-­‐tip s pread d istance of s ide h orns from the s kulls of
• 29 k illed and
• 155 living lizards.
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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The Process of Science: Does Predation Drive
the Evolution of Lizard Horn Length?
– Results: The average horn length and s pread of live lizards is about 1 0% greater than that of killed lizards.
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Fi g u re 1 3 .1 6
(a) A f lat-­‐tailed h orned lizard Length ( mm)
Killed
10 Killed
0
(b) The r emains o f a lizard impaled by a shrike
Live
20
Live
Rear h orns
Side h orns
(tip t o t ip)
(c) R esults o f measurement o f lizard h orns
How Does Evolution Happen?
1. Natural Selection
2. Sexual Selection
3. Genetic Drift
4. Gene Flow
All of these r equire genetic diversity – so mutation is a r equirement for all evolution
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Sexual Selection • When a genetic trait becomes more abundant in a population because it helps you to get more mates, not because it helps you live longer. Examples??
How does evolution happen?
1. Natural Selection
2. Sexual Selection
3. Genetic Drift
4. Gene Flow
All of these r equire genetic diversity – so mutation is a r equirement for all evolution
Genetic Drift: More about genotype
Genetic drift is: – A change in the gene pool of a s mall EX: The population
bottleneck – Tends to reduce genetic d ifferences effect:
between populations
• Results from a drastic reduction in population size
• Due t o chance
Original
population
Zannie Dallara Bottlenecking
event
Surviving
Figure population
1 3.23-­‐3
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Bottleneck Example • Bottlenecking in a population usually reduces genetic variation because at least some alleles are likely to be lost from the gene pool.
• Elephant Seals experienced a genetic bottleneck about 160 years ago
• The founder effect is likely when a few individuals colonize an isolated habitat and represent genetic drift in a new colony. Example of founder effect
Amish: All descend from 2 00 G ermans
• High incidence of polydactyly
How does evolution happen?
1. Natural Selection
2. Sexual Selection
3. Genetic Drift
4. Gene Flow
All of these r equire genetic diversity – so mutation is a r equirement for all evolution
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Bio 1 1 -­‐ EVOLUTION -­‐ How Populations Change
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Genetic Flow
More about Phenotype
• Is genetic exchange with another population • Tends to reduce
genetic differences between populations
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