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The Theory of Evolution
Evolution is a theory
A theory is a hypothesis that has been tested
again and again by many scientists, their
results only support the hypothesis- they never
refute it.
Scientific Theories:
DNA structure (Watson and Crick)
Round Earth
Evolution of Species
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Evolution
Evolution is the change in
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species over time.
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Darwin
Sailed on the H.M.S. Beagle
He noticed:
Plants and animals are well
suited for their environment
Those that are well adapted
survive to produce offspring.
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Galapagos Islands:
Darwin studied beaks of finches
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He realized:
Animals living on
different islands
had once been
members of the
same species.
They adapted to
different
situations
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Darwin’s Theory of Natural
Selection
Individuals better adapted
(to escape, obtain food, hide
etc.) are more likely to
survive.
Traitsof surviving
organisms will be passed
on to the next generation
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Natural Selection stemmed from
two ideas:
1. Organisms usually produce
more than enough
(sometimes even way too
many) offspring
All individuals are different
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2.
(genetic variation).
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Natural Selection
Struggle for Existence – Species compete for
resources
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Natural Selection
Survival of the fittest – the
best adapted will survive.
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Natural Selection
Decent with
modification – all
living species have
descended (with
changes) from other
species.
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Variation is provided by nature
Mutations
When mutations are beneficial
the organism is more likely to
pass on these genes.
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Evidence of Natural Selection
Predator-Prey relationships
Camouflage
Mimicry
The Mimic Octopus (All Three Pictures!!)
Mimics: flatfish, sea snakes, jawfish,
mantis shrimp, lionfish and others!
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Structural Adaptations
•Long necks in a giraffe
•Webbed feet in a duck
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Evidence for Evolution
•Homologous Structures: different
structures with the same evolutionary
origin.
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Evidence of Natural Selection
Fossils
Ancient fossils are never
found in new rock layers.
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Evidence for Evolution
Vestigial Structures: no function in present
organism ~ may have had use in ancestral
organism.
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Evidence for Evolution
Embryology:
Fish, reptile, bird and mammal all have gill
slits as embryos.
Embryos very similar in many stages of
development.
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Biochemistry:
DNA Codons alike throughout all life
forms.
DNA sequences differ depending on
evolutionary relationships.
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Blue People of Kentucky
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15.2 Population Genetics
The frequency that any one allele is seen
in the population is called the allele
frequency.
Is the frequency of the dominant
Huntington’s allele high?
Is the frequency of
the dominant allele
causing 6 fingers high?
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15.2 Population Genetics
If the frequency of the
alleles doesn’t change
over time, the population
is at genetic
equilibrium.
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15.2 Population Genetics
When alleles are brought in and out of
a population due to migration of
individuals, it is called gene flow.
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15.2 Population Genetics
When isolated chance events
can alter gene frequencies in a
population (therefore
disrupting gene equilibrium)
you have what is called genetic
drift.
Common in small isolated
populations such as the Amish of
Lancaster, PA.
Darwin’s finches (perhaps).
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15.2 Population Genetics
Types of selection:
When natural selection of a trait favors the
average individuals in the pop. it is called
stabilizing selection.
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15.2 Population Genetics
Types of selection:
When natural selection favors both extreme
phenotypes of a trait in a pop., it is called
disruptive selection.
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15.2 Population Genetics
Types of selection:
When natural selection favors one extreme
phenotype of a trait, it is called directional
selection.
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15.2 Population Genetics
Type of Selection??
Grey mice are preyed upon but black and
white mice are left alone?
Disruptive
The longer a giraffe’s neck gets the more
food is available, while short necked giraffes
die of starvation before they can reproduce?
Directional
A slow gazelle is easily caught by a cheetah,
but one too fast breaks its legs easily and is
eaten by hyenas?? Stabilizng
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15.2 Population Genetics
Artificial Selection:
Selection for traits that
are determined and
monitored by man.
Ex. Breeding animals such
as dogs or cats.
Sexual Selection:
Selection by one gender
for another gender.
Ex. Peacock feathers, body
hair disappearance in
humans, walrus tusks.
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15.2 Speciation
Speciation is
when a new species
is formed. This
means that the
individuals in the new
species can no longer
produce successful
offspring with the
population from
which they came.
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15.2 Speciation
Geographic Isolation can
cause speciation over long
periods of time.
The seperated organisms are
adapting to different
environments and responding
differently.
Eventually if a mating is
attempted, they can no longer
produce successful offspring
with one another.
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15.2 Speciation
Reproductive Isolation is when a
population can no longer successfully
interbreed with its parent population
(the pop. it came from).
Reproduction if attempted will fail.
Ex. One group breeds
in the fall, one in the
spring and over time
the populations become
new species incapable
of interbreeding. 39
15.2 Speciation
Changes in chromosome number can
cause speciation.
Some cases of polyploidy (more
common in plants) produce individuals
that can only mate with other
polyploids in a pop.
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15.2 Speciation
Can occur rapidly
Punctuated Equilibrium
Gould
Can occur very slowly
Gradualism
Darwin
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15.2 Patterns of Evolution
Adaptive Radiation: When an ancestral
species evolves into several different species,
each filling a specific niche.
Darwin’s finches
Hawaiian Honeycreepers
(p. 420).
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http://www.biology-online.org/images/darwin_finches.jpg
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15.2 Patterns of Evolution
Divergent Evolution: Species that once
were similar or closely related become
very different.
New Species are very different from
each other.
Ex. Adaptive Radiation
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15.2 Patterns of Evolution
Convergent Evolution:
Unrelated species that live
in similar environments
evolve the same
adaptations in order to
survive.
Ex. Tasmanian Wolf and
North American Wolf.
P. 421: Unrelated species
of cacti.
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Important Study Tips!
14.2 Terms
Scientists
Homologous/Analogous/Vestigial Structures
Stabilizing/Directional/Disruptive Selection
Allele Frequency
Gene Pool/Gene Flow
Genetic Drift/Genetic Equilibrium
Convergent/Divergent Evolution
Adaptive Radiation
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Chapter 14.2 Vocabulary
Chemosynthesis
Spontaneous Generation
Biogenesis
Protocell
Prokaryotes
Archaebacteria
Francesco Redi
Louis Pasteur
Alex. Oparin
Miller and Urey
Lynn Margulis
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Chapter 15 Vocabulary
Theory Embryology Geographic Isolation
Evolution Gene Pool Reproductive Isolation
Species Allele Frequency Punctuated Equilibrium
Fossils Genetic Equilibrium Gradualism
Geographic Isolation Gene Flow Adaptive Radiation
Natural Selection Genetic Drift Divergent Evolution
Camouflage Stabilizing Selection Convergent Evolution
Mimicry Disruptive Selection
Homologous Directional Selection
Structures Artificial Selection
Analogous Structures Sexual Selection
Vestigial Structures Speciation
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Chapter 14.2 Map
Define the following words:
Spontaneous Generation
(abiogenesis)
Biogenesis Protocell Chemosynthesis Archaebacteria
Describe each person’s experiment and what they proved or disproved:
Francesco Redi Louis Pasteur
Alexander Oparin Stanley Miller and Harold Urey Lynn Margulis
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Chapter 15.1 Concept Map
Charles Darwin The Origin of
Species by
Artificial Selection Natural Selection Natural
Selection
Homologous Structure Examples:
Adaptations
Analogous Structure Examples:
Mimicry
Vestigial Structures Examples:
Camouflage
Embryological Development Examples:
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Chapter 15.2 Concept Map
Gene Pool
Different Types of Natural Selection Allelic Frequency
example Stabilizing Selection Genetic Equilibrium
example Directional Selection Genetic Drift
example Disruptive Selection
Speciation
Geographic Reproduction Polyploid Gradualism
Isolation Isolation
example example example example 52
14.2 Scientists
Francesco Redi: Disproved that meat
produced maggots by putting meat in a
jar and covering it with cheese cloth.
Louis Pasteur: Proved that
microorganisms such as bacteria did not
did not just arise from air- the final
experiment in disproving spontaneous
generation.
Alexander Oparin: Hypothesized that
life began in the oceans. He said that
the sun, lightning, rain, and various
chemicals came together to form the
first life forms.
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14.2 Scientists
Miller and Urey: Devised an
apparatus and process by which life
molecules such as amino acids and
sugars could be produced from
ammonia, methane, hydrogen, and
water vapor when electricity
simulating lightning was introduced.
Lynn Margulis: Responsible for the
endosymbiant theory.
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