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Evolution Evolution
Chapters 16 & 17 Darwin’ss Voyage
Darwin
Voyage
Chapter 16
Evolution
• Change over time
Change over time
Charles Darwin
Charles Darwin
• Developed
Developed a scientific theory that explains a scientific theory that explains
how modern organisms evolved over long periods of time through descent from
periods of time through descent from common ancestors. Darwin’ss Voyage
Darwin
Voyage
• 1831: Darwin sailed around the world in the HMS Beagle making observations and collecting evidence. • Most of his work was done at the Galapagos Islands, located 100 km west of
Islands, located 100 km west of South America. • 1859: Darwin publishes Origin of the Species.
Darwin’ss Observations
Darwin
Observations
1.) Different, yet similar, animal species 1.)
Different, yet similar, animal species
inhabited separated, but similar, habitats around the globe. 2.) Different, yet related, animal species 2.)
Different, yet related, animal species
occupied different habitats within a local area.
3.) Some fossils of extinct animals were similar to living species.
to living species. Ideas that Shaped Darwin
Public Perception
Public Perception
• All
All life was only a few thousand years life was only a few thousand years
old. • Since
Since its creation, not much had its creation, not much had
changed.
Scientists that Influenced Darwin
Scientists that Influenced Darwin
• ((1785) James Hutton: Using geological examples, 85) Ja es utto : Us g geo og ca e a p es,
concluded that the earth must be much older than a few thousand years. • (1798) Thomas Malthus: Reasoned that if the human population grew unchecked, their wouldn’t be enough space and food for everyone. • (1830) Charles Lyell: Argued for uniformitarianism, which holds that the geological processes we see today
which holds that the geological processes we see today must be the same ones that occurred long ago. Jean Baptiste Lamark
• (1809) Published a theory on evolution that suggested organisms could change during
suggested organisms could change during their lifetimes by selectively using or not using parts of their bodies. These acquired traits
parts of their bodies. These acquired traits could then be passed onto their offspring. • What is wrong with this theory???
Natural Selection
Natural Selection
Words to Know
Words to Know
fitness: the ability to survive and reproduce
fitness: the ability to survive and reproduce
adaptation: an inherited characteristic that d
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i h i d h
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increases an organism’s chance of survival
• Adaptations increase an organism’s fitness.
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Natural Selection
Natural Selection
• AKA:
AKA: survival of the fittest
survival of the fittest
• Selected traits increase an organism’s fitness. • No human involvement. (Unlike selective h
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breeding.)
For Natural Selection to Occur:
For Natural Selection to Occur:
1 The
1.
The population must be limited in size, which population must be limited in size which
creates competition.
(Competition: when two organisms want the
(Competition: when two organisms want the same resource at the same time.)
2 Genetic variation (of inherited traits) must 2.
G
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exist.
Sources of Variation
3. This variation must affect the organism’s reproductive success.
Recipe for Evolution
Descent with modification
Descent with modification
• Species descend from other species over time.
Species descend from other species over time
Ex: dogs descended from wolves.
Common descent: all things, living and extinct have common ancestors
common ancestors
Evidence of Evolution
Evidence of Evolution
Evidence of Evolution
Evidence of Evolution
1 Structural adaptations
1.
Structural adaptations
A. Mimicry: one species resembles another species
B Camouflage: species blend in with surroundings
B.
Camouflage: species blend in with surroundings
Evidence of Evolution
Evidence of Evolution
2 Behavioral adaptations
2. Behavioral adaptations
a. Migration b Courtship
b. Courtship
c. Defending or claiming territory
d C
d. Cooperation (Ex: hunting in packs)
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k)
e. Kin selection: helping a relative survive because they share the same genes
they share the same genes
f. Communication (visual, chemical, sound, language)
More evidence…
More evidence…
3 Fossils
3. Fossils
4. Geographic Distribution of Species (similar, G
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but unrelated species live in different parts of the world)
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ld)
And more evidence…
And more evidence…
5. Homologous structures: basic arrangement of 5
Homologous structures: basic arrangement of
bones in body structures of different species is similar
is similar
ex: bird wing and whale flipper
Note: Not to be confused with analogous structures
Note: Not to be confused with analogous structures (have the same function, but different s uc u es)
structures)
And more evidence…
And more evidence…
6. Vestigial structures: body structures that 6
Vestigial structures: body structures that
serve no purpose in the present day organism
ex: an ostrich’s wings
And more…
And more…
7 Similarities in early development
7. Similarities in early development.
8 i h i
8. Biochemistry: comparing the DNA and RNA i
h
d
All Living Things are All
Living Things are
Related
Evolution Misconceptions
Evolution of Populations
Evolution of Populations
Chapter 17
Populations, NOT individuals evolve!
Populations, NOT individuals evolve!
Gene pool: all of the alleles of a population’s genes
Relative frequency = # certain allele x 100%
total # alleles
total # alleles
Ex: attached earlobes
***Let’s calculate this for our class!
Genetic equilibrium: when the relative frequency remains the same over several generations
• If the relative frequencies in a gene pool change, EVOLUTION has probably occurred!
Sexual vs. Asexual Reproduction
Sexual vs. Asexual Reproduction
• The
The two main sources two main sources
of genetic variation in sexually reproducing organisms is through mutations and genetic recombination.
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• The
The main source of main source of
genetic variation in asexually reproducing organisms is through mutations only.
Natural Selection on Single Gene Traits
Natural Selection on Single Gene Traits
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Hands Up
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Hands Up
Hands Down
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Hands Down
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Before the Predator
After the Predator
Natural Selection on Polygenic Traits
Natural Selection on Polygenic Traits
• Because a polygenic trait is controlled by more than one gene, a wide spectrum of phenotypes are observed.
p
yp
***Let’s calculate this for our class using height.
• Three types of natural selection:
– Directional
– Stabilizing
– Disruptive
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Average Height
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Average Height
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0
150 160
150
160 165 165 170
170 180 180
cm cm cm cm cm
Directional Selection
Directional Selection
• Natural
Natural selection favors selection favors
one of the extreme variations of the trait, so the entire graph moves. • Ex: height, beak lengths
Stabilizing Selection
Stabilizing Selection
• Natural
Natural selection that selection that
favors the average individuals in a population. • Ex: birth weight
Disruptive Selection
Disruptive Selection
• Individuals
Individuals with either with either
extreme variation are selected for. (The average drops.)
• Ex: Light and dark colored limpets
Speciation
• Occurs when members of the same population can no longer interbreed to produce
interbreed to produce fertile offspring.
• Can occur from geographic, behavioral or reproductive isolation.
Divergent vs. Convergent Evolution
Divergent vs. Convergent Evolution
Divergent evolution: Divergent
evolution:
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Convergent evolution: t
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members of one species members of different become less and less species evolve similar
species evolve similar alike, eventually traits because of their resulting in separate environment.
species
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The Effect of Small Populations
The Effect of Small Populations
Genetic drift: a change in allele frequencies due Genetic
drift: a change in allele frequencies due
to something other than natural selection
Ex: Ashkenazi Jews the Amish the Holocaust
Ex: Ashkenazi Jews, the Amish, the Holocaust
Specific types of genetic drift are…
Founder effect: a small group starts a new population elsewhere and their particular
population elsewhere and their particular genes become prevalent
Bottleneck effect: a natural disaster drastically reduces the population
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