Evolution Learning Targets 1-17

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EvolutionLearning Targets 1-17
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Guided Reading Review
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Charles Darwin
LT 1

• HMS Beagle

• Born in England in 1809
• A Naturalist (studied nature)
• Took a 5yr voyage on a ship called the HMS Beagle
  to study the organisms encountered on the journey
• Traveled to the Galapagos Islands near S. America
• Here he made many observations about the
  organisms he saw there including tortoises and
  finches

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Darwins Observations

• Each island of the Galapagos have a different
  climate.
• Found that tortoises had different shells
  depending on the island they inhabited

• Found that finches had different beaks
• He also found fossils similar to living organisms
  and some like he had never seen before

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The Ride Home

• After leaving the Galapagos Islands, Darwin had a
  few questions.
• Why do organisms have differences based on their
  habitat?
• Why had so many species disappeared?
• How are they related to those still living?
• Were similar organisms formerly the same species?

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Guided Reading Review
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Other Old Dead Dudes
LT 2

• Darwin, being a good scientist, studied the works
  of other scientists in and outside of his field.

Malthus
HMS Beagle
Economist
Darwin
Hutton
Lamarck
Naturalist
Lyell
Geologists
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What Darwin Concluded

• Charles Darwin

• What everyone else thought

• From Hutton and Lyell
• If the Earth can change, can life also change?
• Geological processes take a long time, therefore
  the Earth must be old.
• From Malthus
• That organisms will have more offspring than will
  die and this will lead to competition.
• Not all offspring live so what makes some survive
  and others
• die?

• The Earth was made as it was now and did not
  change
• The Earth is only a few thousand years old
• Organisms dont change
• Darwins conclusions caused a BIG buzz

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Guided Reading Review
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That Other Guy

• All living things change over time
• Living things descend from other living things
• Organisms adapt to their environment
• Selective USE or DISUSE of organs will cause
  organisms to gain or lose the trait during their
  lifetime
• Traits lost or gained will be passed onto the
  organisms offspring.
• Loss or acquisition of a trait is to move toward
  being perfect and better suited for their
  environments

• Jean Baptiste Lamarck

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Lamarck
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Guided Reading Review
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Darwins Idea

• Knowing that his ideas were not going to be well
  received, Darwin wrote a book called On the
  Origin of Species, but did not publish it for a
  long time.
• His idea was
• Natural Selection (nature selects organisms to
  survive based on the most favorable trait for the
  environment)
• Every species has variations within a trait and
  the variations are IMPORTANT
• Some of the traits were inheritable
• Those organisms that have favorable traits
  (ADAPTATIONS) will survive and go on to have more
  offspring (FITNESS)
• SURVIVAL OF THE FITTEST
• Over many generations, an adaptation could spread
  throughout the entire species.
• In this way, according to Darwin, evolution by
  natural selection would occur.

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Noodle Worms

• Post Noodle Worm Lab we can say
• Variations do exist within the population
• (green, orange, white worms)-Where did it come
  from? Why Genetics, silly!
• Some worms did struggled to survive.
• Those that did live were best suited or most
  fit and possess a color characteristic that
  makes them more likely to survive.
• Those that survived can pass their characteristic
  to the next generations (a.k.a descending with
  modifications)

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Variations

• So do variations exist in all populations?
• How do they go from parent to offspring?
• Meiosis
• Cells copy DNA
• Crossing over events take place
• in Prophase I
• Fertilization from SEXUAL reproduction
• Egg Sperm
• Individual sets of chromosomes combine to form
  offspring with features unique from either parent

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Variations

• Mutations
• By Chance, radiation, and chemicals
• Give new genetic material to the gene pool
• Genetic Drift
• Migration/Gene Flow

All of these forces change GENOTYPES, PHENOTYPES,
and determine the amount of GENETIC VARIATION
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Variations

• Gene pool all members of an interbreeding
  population who bring genetic variety to the
  population.
• So all the BB, Bb, or bb
• in the buffalo herd ?
• Relative frequency percentage of time a
  particular allele appears in the gene pool
  compared to other alleles
• What is the of Bs to the of bs in the
  buffalo herd ?

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Putting It All Together
LT 5
Evolution (Darwin) 1859
Genetics (Mendel) Mid 1800s
DNA (Watson Crick) 1963
Current Understanding of Biological Evolution
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Putting It All Together

• Okay, thenso,
• Based on the Mouse WS and the Moths Activity,
• Evolution a change in the relative frequency of
  alleles in a population over time
• Evolutionary fitness the success with which an
  individual can pass their traits to the next
  generation
• Therefore, POPULATIONS, NOT INDIVIDUALS, evolve

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Putting It All Together

• Evolution NEVER acts DIRECTLY on ONE GENE.
• Evolution works on the entire organism
• If the organism has evolutionary fitness and
• Reproduces gene(s) in the gene pool
• Does not reproduce NO gene(s) in the gene pool

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NS on a Single Gene Trait

• Single gene trait one gene controls a trait.
• Only two phenotypes (Widows peak or no widows
  peak)
• Three genotypes (WW, Ww or ww)
• Two alleles (W and w) in this example
• Natural selection can work on
• each phenotype and change
• the allelic frequency

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NS on a Polygenic Trait

• Polygenic Trait- when a trait is controlled by
  more than one gene
• A range of phenotypes (a bell curve)
• Many genotypes
• At least two alleles per gene
• Natural selection effect is more
• complex
• fitness of individual close on
• curve is similar
• fitness of individuals further
• apart is varied. This is where
• NS can act.

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NS on a Polygenic Trait

• Three Effects on Phenotypes
• Directional Selection - when one end of the curve
  has higher fitness than the middle or other end
  of the curve
• Shifts the
• curve left
• or right

Peccaries eat cacti. Cacti with fewer spines are
eaten first. Thus, the cacti with more spines
fair better . NS moves the curve toward cacti
that make many spines
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NS on a Polygenic Trait

• 2. Stabilizing Selection when individuals in
  the middle of the curve have higher fitness than
  those on the ends.
• Narrows
• the graph

Peccaries continue to eat the cacti with few
spines (left of graph). A parasitic insect lays
its eggs at the cacti spine base and therefore
loves cacti with lots of spines (right of graph).
Both extremes are NOT fit. Being in the middle
is best
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NS on a Polygenic Trait

• 3. Disruptive Selection when individuals at the
  upper and lower ends of the curve have higher
  fitness
• Creates 2
• peaks in graph
• /phenotype

A road through the desert brings tourists that
love to pick cacti as souvenirs. Too few spines
on the cacti look bad and too many spines are
hard to pick. Thus, cacti with spine numbers in
the middle are picked.
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Other Factors of Evolutionary Change
4. Genetic Drift
Variation (crossing over, meiosis, sexual
reproduction, and mutations)
5. Migration
Natural Selection
NoteNS does not create variation, it just works
on it
Evolutionary Change
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Genetic Drift
LT 6

• Genetic drift is evolution BY CHANCE! changes
  in a population that result from random chance or
  luck
• Luck ? evolutionary fitness
• Luck ? better
• Affects all populations
• Natural selection produces adaptations, Genetic
  Drift does not
• Genes of one generation do not wind up in
  identical ratios in the next generation, butits
  still evolution!

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Genetic Drift

• By random chance, the brown frogs die
• Their genes are thus unable to be passed to the
  next generation
• Thus the gray and greens are the only ones able
  to mate and pass on genes.
• Variation is thereby decreased

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Genetic Drift

• Effects of Genetic Drift
• A decrease in variation within a
  population/change in the relative frequency
• May decrease a populations ability to respond to
  selection pressures
• Acts FASTER and is more DRAMATIC in small
  populations
• Very bad for rare or endangered species
• Can cause new species to emerge

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Genetic Drift

• Population bottleneck a decrease in population
  size for at least one generation
• Causes a decrease in variation
• Worse for small populations (even if for a short
  time)
• Makes responding to selective pressures harder
• Causes
• Overhunting
• Environmental Disaster (hurricane, flood, etc)
• Habitat Destruction

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Genetic Drift

• Founder Effect when a portion of an original
  population breaks off and form a new population.
  
• Also decreases variability because the small
  group may not be equally representative of the
  larger populations variability

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Hardy-Weinburg
LT 7

• Recall that evolution -is the change in the
  relative frequency of alleles in a population
  over time.
• Versus
• Genetic equilibrium - No evolution no changes
  in the relative frequency
• When does this happen? Under what conditions?

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Hardy-Weinburg

• A The relative frequency of alleles in a
  population will remain constant UNLESS 1 or more
  factors cause the frequency to change.
• Five Conditions for GE
• Random Mating
• equal opportunity for all member to produce
  young.
• This is rarely random!
• The population is large
• this decrease the effects of genetic drift

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Hardy-Weinburg

• No immigration or emigration
• Immigration new individuals move in and bring
  new alleles and variety
• Emigration individuals leave the population and
  take allelic variety with them
• No mutations
• No natural selection
• All genotypes have equal
• probability for survival

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Hardy-Weinburg

• For some populations these conditions are met, or
  nearly met, for long periods of time.
• Conditions met genetic equilibrium
• Conditions not met evolution
• There are two equations that can be used to show
  changes.
• p2 2pq q2 1
• p q 1
• Where p dom. allele freq
• and q rec. allele freq

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Geologic Time Evidence for Evolution
LT 9-13

• Please see the Guided Reading Posted to the
  website for the answers and notes for Geologic
  Time and Evidence for Evolution
• (LT 9-13)

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Cladograms
LT 9-13
Lets see one made

• Cladogram a diagram that shows evolutionary
  relationships among groups
• Based on phylogeny (the study of evolutionary
  relationships)
• Sometimes called a phylogenic tree (although the
  two vary slightly)
• Cladistics - the practice of looking at
  innovations, or newer features, that serve some
  kind of purpose
• Derived characteristics new features that
  appear in later generations but not earlier ones

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Cladogram
1. ______ Wings2. ______ 6 Legs3. ______
Segmented Body4. ______ Double set of
wings5. ______ Jumping Legs6.
______ Crushing
mouthparts7. ______ Legs8. ______ Curly
Antennae
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Cladograms

• To make a cladogram, you must first look at the
  animals you are studying and establish
  characteristics that they share and ones that are
  unique to each group. For the animals on the
  table, indicate whether the characteristic is
  present or not. Based on that chart, create a
  cladogram like the one pictured above.

Cells Backbone Legs Hair Opposable Thumbs
Tiger
Slug
Frog
Catfish
Human
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Speciation
LT 14
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Extinction
LT 15

• 99 of all life that has ever existed is now
  extinct
• mass extinctions have occurred many times in the
  Earths history
• Extinctions indicate
• Organisms who were selected against by nature
• A failure to adapt
• A collapse in an organisms environment they
  could not help

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Extinction

• What becomes of those organisms that live
  (evolutionarily speaking, of course)?
• When large groups of organisms die, it leaves
  habitats and niches open for others to move into.
• New habitats can also have new selective
  pressures that will work on organisms.
• This could cause evolution within a species OR
• Adaptive radiation a species has evolved from a
  common ancestor into diverse forms that live in
  different ways

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Types of Evolution
LT 16

• A. Divergent Evolution-when selective pressures
  cause two species to form (think speciation)
• B. Convergent Evolution-takes place when species
  of different ancestry begin to share similar
  traits because of a shared environment or other
  selection pressure.
• C. Co-evolution- organism of different species
  but have a close relationship and evolve
  together

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Rates of Evolution
LT 17

• Darwin?
• believed evolution was a SLOW process Gradualism
• Modern Biologist?
• think that some evolution is slow and other times
  long periods of equilibrium are followed by RAPID
  evolution-Punctuated Equilibrium