Download Evolution and Speciation

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Imagine a population of 200 birds, some red and
some yellow. The red allele, R, is dominant over the
yellow allele, r. There are 72 RR birds, 96 Rr birds,
and 32 rr birds in the population.
◦ What are the genotypic frequencies in the population?
◦ What are the allelic frequencies in the population?
◦ Using the frequencies you calculated in b, what would
Hardy-Weinberg predict the genotypic frequencies should
be? What about allelic frequencies? Is this population in
Hardy Weinberg equilibrium?
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RR = 72/200 = 0.36; Rr=96/200 = 0.48 ; rr= 32/200
= 0.16
R=72 + 72 + 96 = 240/400 = 0.6;
r = 32 + 32 + 96 = 160/400 = 0.4
P=R= Red
q= r = yellow
32/200= 0.16 = yellow = rr= q2
√0.16=√q2
q = 0.4 then p = 0.6
RR = p2 = (0.6)2 = 0.36 = 36.00%
Rr = 2pq = 2(0.6)(0.4) = 0.48= 48.00%
rr = q2 = (0.4)2 = 0.16 = 16.00%
Ms. Kim
H. Biology
 Evolution on a small scale
 Change in allele frequencies from one
generation to the next
 A process that leads to a change in a
species
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Natural selection
Genetic Drift
Gene Flow
Mutation
Sexual Selection
Microevolution explains how
populations evolve
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Origin of different species
 SPECIATION
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Extinction of species
Evolution of major features
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Protective Coloring
◦ Camouflage and Mimicry
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Physiological Adaptations
◦ Reproductive/Hormonal Changes
◦ Color changes
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Behavioral Adaptations
◦ Courtship dances/ songs
◦ “Fighting” tactics
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Also arise in response to environmental
pressures
◦ Temperature, Antibiotic/pesticide resistance
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Animals who have greater fitness survive in
environment and live to reproduce
Random changes in DNA (mutations) can lead
to greater or less fitness
◦ Produced by Sexual Reproduction
◦ Allow for DIVERSITY in a Population
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Adaptations allow an organism to survive
better in their environment
 Directional
◦ Extreme form favored by
natural selection
 Stabilizing
◦ Middle form most successful
 Disruptive
◦ Two extreme forms successful
in separate environments
1. Convergent evolution
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Analogous Structures
organisms that are NOT closely related
independently evolve similar traits as a
result of having to adapt to similar
environments.
2 species acquiring same characteristics from 2
different ancestral species
Ex: Dolphins & fishes
Ex: Wings of bees & bats
2. Divergent evolution
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2 species gradually become different
Often occurs when closely related species
diversify to new habitats
 Formation of 2 descendent species from an ancestral species
Ex: Darwin’s finches
Type: Adaptive radiation
Homologous structures
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Appearance of numerous
species over a short period of
time
Adapted species from a
common ancestor when they
are introduced to new
environmental opportunities
Typically occurs when a few
organisms make their way to
new, usually distant areas OR
mass extinctions occur, which
open up new niches
Dubautia laxa
KAUAI
5.1
million
years
1.3
million
MOLOKAI years
MAUI
OAHU
3.7 LANAI
million
years
Argyroxiphium sandwicense
HAWAII
0.4
million
years
Dubautia waialealae
Dubautia scabra
Dubautia linearis
What type of evolution?
A.Divergent
B.Convergent
C.Coevolution
What type of evolution?
A. Divergent
B. Convergent
C. Coevolution
3. Coevolution
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2 organisms evolve (change) in response
to each other
Insects and the flowers (ex: orchids) they
pollinate
4. Parallel Evolution
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2 species evolve independently of each
other, maintaining similar traits
Usually occurs between unrelated
species (but similar ancestors) that do
NOT occupy the same or similar
habitats
◦ Ex: Eutherians (placental) and Marsupial
mammals
What type of evolution?
A. Divergent
B. Convergent
C. Parallel Evolution
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Origin of new
species
How would we
identify if a
species is
“new”?
Two Basic Patterns of
Evolutionary Change
 Anagenesis
(phyletic evolution)
◦ transforms one species into
another
 Cladogenesis (branching evolution)
◦ the splitting of a gene pool,
giving rise to one or more new
species
Anagenesis
Cladogenesis
 Gradualism
◦ Species change slowly
(gradually) over time
 Punctuated Equilibrium
◦ Species can make rapid
“leaps” in evolution
Time
Gradualism model
Punctuated equilibrium model
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Species is a Latin word meaning “kind”
or “appearance”
◦ A population of organisms that
produces viable fertile offspring in
nature.
◦ They can NOT interbreed with other
populations
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CASE 1
A mule is the offspring of a female
horse and a male donkey. In contrast,
the hinney is the offspring of a male
horse and female donkey. The mule is
easier to breed and larger in size than
the hinney. For these reasons, the mule
became an important domesticated
animal. Horses have 64 chromosomes,
donkeys have 62. The mule has 63 and
cannot evenly divide, that is why the
animal is sterile.
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CASE 2
A liger is a cross between a female
tiger and a male lion. In contrast, the
tigon is a cross between a male tiger
and a female lion. These two species
do not breed in nature because their
habitats are so different. Lions live
in open grasslands while tigers live in
forests. In captivity, it is possible to
produce ligers and tigons. Male
ligors are sterile, but female ligers
are fertile and may reproduce with
either tigers or lions.
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CASE 3
E.coli is a bacterium normally found in
the intestines. It is harmless and may
actually be beneficial to the human
digestive system. There is a pathogenic
strain of E.coli that produces a toxin
that can kill its human host. The two
strains look very similar under a
microscope. Comparison of their
genomes reveals that the pathogenic
strain lacks 528 genes found in the
normal strain and has 1,387 genes not
found in the normal strain.
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5 Types:
 Morphological
 Group of individuals sharing similar characteristics
 Recognition
 Behavior/chemical recognition between individuals
 Genetic
 Range of variation in DNA- similar in individuals
 Cladistic
 Species defined as a branch in a cladogram
 Biological
 Group of individuals capable of interbreeding
Similarity between different species  different behaviors and songs
Diversity within a species  defined by capacity to interbreed.
Speciation
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Speciation = the origin of new species
◦ Must explain how new species originate and how
populations evolve
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Microevolution (genotype evolution)
◦ adaptations that evolve within a population’s gene pool
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Macroevolution (phenotype evolution)
◦ refers to evolutionary change at the population level
◦ Major biological changes evident in the fossil record