pre Darwinian

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pre Darwinian

• Review who these men are Timeline of
  Evolutionary Thought
• Charles Darwin, Alfred Russel Wallace, and Gregor
  Mendel laid the foundations of modern
  evolutionary theory.

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Theories of Evolution

• Lamarck
• Darwin

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Lamarcks Theory

• Jean Baptiste de Lemarck, 1809
• First theory of evolution- how species change
• Believed organisms constantly strive to improve
  themselves

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Lamarcks Theory

• Law of use and disuse- parts used by animal more
  became stronger, parts used less become weaker
• Inheritance of acquired characteristics-
  characteristics gained from law of use and disuse
  passed to future generations

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Lamarcks Theory

• Used the giraffe as an example
• Giraffe necks were originally short
• Starting stretching their necks to get at food
  (Use/disuse)
• Pass traits of longer necks to next generation

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Darwin and Wallace

• Charles Darwin 1859 and Alfred Russel Wallace-
  came to same conclusions working separately
• Work led to theory of natural selection

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• Darwin video
• Evolution do to teacher student pages and see
  various video and documents about this man.

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Darwins voyage to the Galapagos

• 1831- voyage on HMS Beagle
• Observations there helped lead to theory of
  evolution
• Galapagos finches- various species of finches
  with slight differences (beak size and diet)

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Darwins Finches
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Those beaks

• How about that vampire finch? Video "Vampire
  Birds" of the Galapagos Islands

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Darwin's observations

• 1. Species have the ability to produce more
  offspring than is necessary to replace themselves
  (superfecundity)
• Influenced by Mathis

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• 2. There is a finite pool of resources that is
  smaller than necessary to allow all offspring to
  survive
• Consider the point that there are limited
  resources needed for survival. There is
  competition and a struggle for existence

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• 3. Natural populations are of constant size (over
  the long term)
• This means that many are born and few survive.
  Just enough to balance the population with the
  resources.

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• 4. Individuals within a species vary in many
  characteristics.
• Think in terms of advantage.
• In the environment if the individual has an
  advantage they will receive more of the finite
  resources. This in turn allows them to reach
  reproductive age.

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• 5. Much of that variation is heritable.
• Those genes which provided the advantage are
  now passed down to the offspring. This alters
  the genes in the gene pool causing change. The
  population is best suited for that environment.

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Darwin's inferences

• 1. Individuals compete (or otherwise struggle
  with each other) for limited resources

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• 2. Only some individuals survive to reproduce
• those that more successfully obtain
  resources are more successful

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• 3. Over many generations, a population will
  consist of the most successful kinds of
  individuals
• These ideas were radical and Darwin waited for a
  long time to publish his work.
• Evolution Library Darwin Reluctant Rebel

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• Changes in o genetic instructions change the
  proteins that are made. This may lead to a more
  fit protein for the environment.
• Teachers' Domain An Origin of Species
• Natural selection Evolution Library Evolution
  of Camouflage
• Evolution Library Evolution of the Eye

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• Watch this and thing about the advantage this
  mutation may provide.
• Teachers' Domain Double Immunity
• Watch this for a study which has documented
  evolution.
• Teachers' Domain Evolving Ideas How Does
  Evolution Really Work?

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• There are adaptations (allele combinations) which
  are successful and those which are a
  disadvantage. One of these is the Heterozygous
  Advantage.
• Teachers' Domain Sickle vs. Normal Cell

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Natural Selection

• Nature selects the members of the population that
  will survive and those individuals with favorable
  variation will have better chance to survive
• Favorable variations occur by ACCIDENT, not
  intentional
• Could be just random changes in DNA

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Natural Selection

• Variation exists within populations
• Genetic variation can be passed on to later
  generations
• Some types of variation will increase chances of
  survival and reproduction
• Young of those with genetic advantage will
  continue to pass their genes to later generations
• Over long periods of time, changes will impact
  the entire population

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Darwins Theory

• Overproduction- more offspring born than survive
• Competition- members of a species compete for
  food, habitat, etc.
• Variation- differences in traits, features
  inherited from parents to offspring

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Darwins Theory

• Adaptations- any inherited trait that improves
  survival
• Natural selection- survival of the fittest
• Speciation- If enough changes take place, new
  species may be formed

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Keep in mind

• Populations or species evolve, not individuals

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Lamarck vs. Darwin
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Stabilizing selection

• When selective pressures select against the two
  extremes of a trait, the population experiences
  stabilizing selection. For example, plant height
  might be acted on by stabilizing selection. A
  plant that is too short may not be able to
  compete with other plants for sunlight. However,
  extremely tall plants may be more susceptible to
  wind damage. Stabilizing Selection

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Directional selection

• In directional selection, one extreme of the
  trait distribution experiences selection against
  it. Using the familiar example of giraffe necks,
  there was a selection pressure against short
  necks, since individuals with short necks could
  not reach as many leaves on which to feed. As a
  result, the distribution of neck length shifted
  to favor individuals with long necks.
  Microevolution go to peppered moth and
  directional selection.

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Disruptive Selection

• In disruptive selection, selection pressures act
  against individuals in the middle of the trait
  distribution. The result is a bimodal, or
  two-peaked, curve in which the two extremes of
  the curve create their own smaller curves.
  Disruptive Selection

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• eLearning ( go to right column and look for
  types of selections )

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Industrial Melanism

• The peppered moth. Two forms (morphs) the gray
  mottled form and the dark melanic form. Changes
  in relative numbers was hypothesized to be the
  result of selective predation by birds. High
  industrial pollution make the darker moth less
  likely to be seen.

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• Melanin gives color to moths
• Black is a mutation of the white form (morphs),
  it is dominant.
• With industrial polution the black allele became
  favorable. Increase in population of the
  dominant allele.
• Clean air, return of lichen , increase in
  recessive allele.

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Sexual Selection

• Sexual dimorphism used to describe distinctly
  male and female phenotypes or secondary sexual
  characteristics.
• based on any trait that gives the individual a
  competitive edge
• Competition for mating rights.
• Through nonrandom mating, alleles for preferred
  traits increase.
• This leads to increased sexual dimorphism

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Balanced Polymorphism/ Malaria Heterozygous
Advantage

• Balanced polymorphism (having many forms) is the
  maintenance of two or more forms of a trait in
  fairly steady proportions over time. This occurs
  when nonidentical alleles are maintained at
  frequencies greater than one percent.

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• Sickle-cell anemia is an example. In parts of
  Africa, heterozygotes, HbS/HbA, comprise about
  one third of the population.
• It is now known that heterozygous individuals
  are more resistant to the protozoan that causes
  malaria.
• They survive in greater numbers than the
  homozygotes who have sickle cell disease
• The

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Rate of Evolution

• Darwin Wallace
• Gradualism new species come from variations that
  are acquired over long periods of time
• Evolution continuous and slow

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Gradualism
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Rate of Evolution

• Steven J. Gould and Niles Eldredge
• Punctuated Equilibrium Species stay same for
  extended periods of time and then undergo rapid
  periods of evolution

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Punctuated Equilibrium
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Punctuated Equilibrium
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Genetics and Evolution

• Evolution changes populations
• Populations group of organisms of the same
  species living together in a given region and
  capable of interbreeding
• Modern theory of evolution evolution happens to
  populations

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Genetics and Evolution

• Population genetics- studying changes in genetic
  makeup
• Copy these
• Allele frequencies- how common certain alleles
  are in a population
• Gene pool- all of the alleles that are present in
  a population

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Genetic Sources of Variation

• Mutations
• Genetic recombination
• Migration
• Genetic Drift

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Mutations

• Gene and chromosomal mutations lead to genetic
  variation
• Gene mutations are rate 1/10,000 gametes
• Lots of genes make up organisms- so chances of
  having mutated gene are very possible
• Chromosomal mutations- make new combinations
• Mutations may be good or bad or have no effect
• Good mutations will be selected for by the
  environment

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Genetic Recombination

• Sexual reproduction leads to variation!
• Genetic recombination form new allele
  combinations from sexual reproduction
• Crossing over- swap parts of homologous
  chromosomes
• Independent assortment- gametes get random
  grouping of chromosomes

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Migration

• Organisms may move in or out of a population
• Carry a unique set of genes with them!
• Impacts small populations

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Genetic Drift

• Genetic drift change in gene pool of a small
  population by chance
• Small population- greater chance of losing
  alleles unique to small group of population
• Decreases variation? not good for health of
  species!
• Genetic Drift

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Genetic Drift

• Genetic Drift Simulation
• gene frequencies change randomly
• particularly prevalent in small populations.
• Genetic Drift

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So what is it?

• A term that describes the random fluctuations in
  a gene pool over time. In large populations, the
  effects of genetic drift are negligible.
• In small populations like we just saw the impact
  can be big

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Genetic drift
In what population will the loss of a purple fish
have a bigger impact? Why?
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Hardy-Weinberg Law

• States that sexual reproduction does not cause
  change in allele frequency (how often alleles
  occur)
• Random mating prevents the frequency of alleles
  from changing
• Law is theoretical- does not apply to real life
  conditions (need specific conditions to be met)

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The Hardy-Weinberg Law

• The unifying concept of population genetics is
  the Hardy-Weinberg Law (named after the two
  scientists who simultaneously discovered the
  law). The law predicts how gene frequencies will
  be transmitted from generation to generation
  given a specific set of assumptions. Specifically

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The If and then of it all

• If an infinitely large, random mating population
  is free from outside evolutionaryforces (i.e.
  mutation, migration and natural selection),

• then the gene frequencies will not change over
  time and the frequencies in the next generation
  will be p2 for the AA genotype, 2pq for the Aa
  genotype and q2 for the aa genotype.

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Assumptions

• large population - to insure no sampling error
  from one generation to the next
• random mating - no assortive mating or mating by
  genotype
• no mutations - or mutational equilbriumeven new
  mutations have little effect on allele
  frequencies from one generation to the next
• no migration between populations
• no selection - all genotypes reproduce with equal
  success

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Basic Relations

• two alleles at a gene - A and a
• frequency of the A allele p
• frequency of the a allele q
• p q 1
• 1 - q p

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• Or in a video these conditions would look
  likehttp//zoology.okstate.edu/zoo_lrc/biol1114/tu
  torials/Flash/life4e_15-6-OSU.swf

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• Another example animation
• eLearning go to animation hardy weinberg
• http//www.lakesideschool.org/upperschool/departme
  nts/science/bio/documents/hardy2.swf

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Demo problems

• How to do the Hardy Weinberg.
• Hardy-Weinberg Problems

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• Go to workbook pages 110- 111

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Founder effect workbook 115

• Founder
• Remember the Amish. A small population which
  moved into the Penn. area of North America. One
  of the founders carried a gene for polydactylism.
  This gene was isolated to this tight knit
  community and the result is seen in the progeny
  today

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Bottleneck page 116

• Sudden reductions in population size can also
  alter the resulting gene pools. Any environmental
  condition in which many individuals are killed
  and only a small number survive, creates a
  bottleneck effect.

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• Northern elephant seals have reduced genetic
  variation probably because of a population
  bottleneck humans inflicted on them in the 1890s.
  Hunting reduced their population size to as few
  as 20 individuals at the end of the 19th century.
  Their population has since rebounded to over
  30,000but their genes still carry the marks of
  this bottleneck they have much less genetic
  variation than a population of southern elephant
  seals that was not so intensely hunted.

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The Cheetah and Florida Panther

• About 10,000 years ago cheetah as a species lost
  99 of population, it is speculated it went down
  to one pregnant female. As a result of the
  population crash, and the subsequent inbreeding,
  a male cheetah has a sperm count that is 90
  percent lower than tigers' and lions'. On top of
  that, 75 percent of the sperm that IS produced is
  abnormal. If cheetahs were livestock, they would
  be classified as infertile.

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Florida Panther

• There are between 30 and 50 Florida Panthers left
  and they are so inbred that the cubs are starting
  to be born with heart defects.

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Genetic Drift

• Genetic Drift Simulation
• gene frequencies change randomly
• particularly prevalent in small populations.
• Genetic Drift

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So what is it?

• A term that describes the random fluctuations in
  a gene pool over time. In large populations, the
  effects of genetic drift are negligible.
• In small populations like we just saw the impact
  can be big

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SPECIATION

• Species are groups of interbreeding natural
  populations that are reproductively isolated from
  other such groups.
• If something prevents gene flow, then you have a
  genetic divergence
• A genetic divergence is a buildup of differences
  between the allele pools of two or more
  populations. Tutorial 24.1 Speciation Mechanisms

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• Go back and look at natural selection Tutorial
  23.1 Natural Selection
• The cost of selectionTutorial 23.3 Assessing the
  Costs of Adaptations

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There are three models for differences in
speciation.

• 1. Allopatric speciation - in the absence of gene
  flow between geographically separate populations,
  daughter species form gradually, by divergence.

• Chapter 4 Animations
• Go to allopatric animation.
• Allopatric speciation
• Tutorial 24.2 Founder Events Lead to Allopatric
  Speciation

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Ring Species

• Evolution Library Ring Species Salamanders

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• Reproductive Isolation is a type of genetic
  isolation. Here the formation of a new species
  can take place in the same geographical area,
  e.g. mutations may result in reproductive
  incompatibility. A new gene producing, say, a
  hormone, may lead an animal to be rejected from
  the mainstream group, but breeding may be
  possible within its own groups of variants. When
  this mechanism results in the production of a new
  species it is known as sympatric speciation.

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• 2. Sympatric speciation - daughter species arise
  from a group of individuals within an existing
  population.

• speciation animations
• Good review of nondisjuction in plants. Need
  to watch all three animations
• Sympatric speciation in wheat.

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Parapatric Speciation

• 3. Daughter species arise due to reproductive
  isolation. Found most often in plants.
• Parapatric Speciation

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• plants exhibiting different degrees of tolerance
  for heavy metals and living in the vicinity of
  mine tailings.

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• reproductive isolation
• mechanisms that prevent two or more populations
  from exchanging genes.
• The separation of the gene pools of populations,
  under some conditions, can lead to the genesis of
  distinct species.

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• Species maintain their genetic distinctiveness
  through barriers to reproduction.
• Fall into two groups
• Prezygote isolation
• Postzygote isolation
• Reproductive isolating mechanisms
• Postzygotic Isolation

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Behavioral isolation

• Evolution Library Isolating Mechanisms
  Lacewing Songs

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Lets look at this all over again.

• digg / video display Carl Sagan and life

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Microevolution

• changes in the gene pool of a population over
  time
• result in relatively small changes to the
  organisms in the population - changes which would
  not result in the newer organisms being
  considered as different species.
• Examples change in a species' coloring or size.

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Macroevolution

• changes in organisms which are significant
• over time, the newer organisms would be
  considered an entirely new species.
• In other words, the new organisms would be
  unable to mate with their ancestors, assuming we
  were able to bring them together.

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Patterns of evolution/Adaptive Radiation

• many related species evolved from a single
  ancestral species
• Usually occurs with new habitat, few competitors
  for resources.

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Patterns of evolution/divergent

• divergent evolution-occurs when a single group of
  organisms splits into two groups and each group
  evolves in increasingly different directions

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Hominid divergent evolution
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Parallel evolution

• parallel evolution-occurs when a group of
  organisms evolve into two ( or more) distinct but
  similar lineages and continue to adapt in similar
  ways for a long period of time, often in response
  to a similar environment
• Note the mouthparts on these lamprey.

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lampreys
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Convergent evolution

• Convergent evolution, when organisms that aren't
  closely related evolve similar traits as they
  both adapt to similar environments.
• Evolution Library Convergent Evolution

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• Thylacoleo - About Australia and the Marsupials
  (page 4)

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Extinction

• Evolution Extinction
• 5 major extinctionsThe Five Worst Extinctions in
  Earth's History
• In The Wild SPOTLIGHT

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Punctuated Equilibrium ( rates of evolution)

• According to the theory of punctuated
  equilibrium, evolution proceeds relatively
  rapidly during speciation between speciation
  events the population remains relatively constant
  in a condition called stasis.
• Evolution - A-Z - Punctuated equilibrium

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Punctuated equilibrium(rates of evolution)

• evolution proceeds relatively rapidly during
  speciation between speciation events the
  population remains relatively constant in a
  condition called stasis.

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Importance of Variation

• Adaptations variation in a population that
  increases survival and reproduction
• Variation can increase/decrease survival of
  species!
• Examples
• Mimicry
• Hibernation
• Camouflage

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Mimicry- resemble a dangerous species
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Mimicry
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Hibernation
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Camouflage
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More Camo
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Speciation

• What are species?
• Speciation formation of a new species
• Happens if accumulate enough differences
• May become separated
• Geographically
• Reproductively
• Polyploidy
• Adaptive radiation- in new environments, become
  different

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• Tutorial 24.1 Speciation Mechanisms