Evolution

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Evolution

• Chapter 15
• Darwins Theory of Evolution

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15-1 The Puzzle of Lifes Diversity

• Biological Diversity- variety of living things.
• Evolutionary Theory- a collection of scientific
  facts, observations hypotheses it can explain
  the diversity of life on Earth.
• Evolution- change over time the process by which
  modern organisms have descended from ancient
  organisms.
• Scientific Theory- a well supported testable
  explanation of natural events supported by
  evidence can be tested with new evidence.

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Charles Darwin

• Contributed more than any other scientist to our
  understanding of evolution.
• Voyage of the Beagle- sailed around the world
  stopping at the Galapagos Islands.
• He made observations collected evidence.
• He noticed many plants animals were well suited
  to their environment.
• He collected fossils- preserved remains of
  ancient organisms.
• He collected many different species he had never
  seen before.

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Evolution- Contributing Scientist Timeline
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Galapagos Islands

• Islands west of South America that are close
  together but have very different climates.
• Darwin studied shell shape of the many different
  tortoises.
• He discovered many similar but different birds
  that turned out to be finches.
• Each species of finch had a different shaped beak
  which was a structural adaptation.
• Darwin felt the animals on all the different
  islands once came from the same species or common
  ancestry.

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Voyage of the USS Beagle
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15-2 Ideas that shaped Darwins Thinking

• He felt that many would find his ideas too
  shocking to accept.
• He began to put all of his work on paper.
• Several scientists influenced Darwin
• Hutton
• Lyell
• Lamarck
• Malthus

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15-3 Darwins Case

• He was reluctant to publish his ideas because
  they were so radical.
• He was disturbed by his own findings which
  challenged fundamental scientific beliefs.
• When he heard a scientist name Wallace had the
  same idea as his, Darwin published his work.

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Darwin Published his Book

• On the Origin of Species 1859.
• The book provided evidence that evolution has
  occurred.
• His theory on how evolution comes about was based
  on artificial selection.
• He believed that natural selection occurs in
  nature.

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Artificial Natural Selection

• Artificial Selection
• Animal breeders select for breeding only animals
  with the desired traits.
• Ex. Crops, livestock horses.
• Natural Selection
• Individuals differ some of the differences can
  be passed on to their offspring.
• More offspring are produced than can survive or
  reproduce.
• Individuals best suited to their environment
  survive reproduce most successfully.
• Ex. run fast, outsmart with behavioral
  tactics.

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Artificial Selection Man Made
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Survival of the Fittest

• Animals prey on other animals. Some die and some
  survive.
• Fitness- the ability to survive reproduce in a
  specific environment.
• Only the fittest organisms pass on their traits,
  thus the species change over time.
• Adaptation- an inherited characteristic that can
  be physical or behavioral.

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Pesticide-Resistant Insects Modeling Adaptations
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Principle of Common Descent

• All species come from common ancestors.
• It links all organisms on Earth into a single
  tree of life.
• Ex. Tigers-panthers-cheetahs,
  felines-horses-dogs-bats, mammals-birds-alligators
  -fish.

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Genetic Evidence of Commn Decent
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4 Types of Evidence to Support Evolution

• 1. Fossil record- comparing fossils from older
  younger rock layers documents the fact that
  evolution has occurred it is a detailed record
  of evolution. Pg. 382,15-13
• 2. Geographical distribution of living species-
  the presence of similar environments suggests
  natural selection. Ex.-the finches could have
  descended from common ancestors on the mainland.
  Pg. 383, 15-14

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4 Types of Evidence to Support Evolution

• 3. Homologous structures of living organisms-
  they have different mature forms but develop from
  the same embryonic tissues. Bone structure is the
  same but they look different. All are adapted to
  survive in different environments. Ex. Legs,
  wings, fins. Pg 384, 15-15
• Vestigial organs- some homologous structures no
  longer serve important functions in descendants.
  Their size is reduces.

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Homologous Structures
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4 Types of Evidence to Support Evolution

• 4. Similarities in early development, or
  embryology- early stages, or embryos, of many
  animals are very similar. Pg. 385, 15-17

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Evolution

• Chapter 16
• Evolution of Populations

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Definitions You need to know

• Genotype The genetic makeup of an organism EX
  genes coding for blue eyes of genes coding for
  brown eyes
• Phenotype The physical appearance coded for by
  the genotype- EX Do you have blue eyes or brown
  eyes?
• Allele The different forms of genes that code
  for different traits

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16-1 Genes Variations

• What we already know
• Traits are controlled by genes.
• Many genes have at least 2 forms (or alleles).
• Individuals of all species are heterozygous
  (meaning they carry genes for trait they dont
  show) for many genes.

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Living Things have 2 copies of every chromosome-
One from the female parent and one from the male
parent
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Figure 14.3 Alleles, alternative versions of a
gene
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Different Alleles code for Different Phenotypes
(physical appearances)
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Genetic Variation

• Studied in populations
• Population- a group of individuals of the same
  species that interbreed share a common group of
  genes.
• Gene Pool- results from interbreeding in
  populations its all the genes that are present
  in a population contains 2 or more alleles
  (forms) for each inheritable trait.
• Relative Frequency- the of times the allele
  (trait) occurs in a gene pool, compared with the
  of times other alleles (traits) for the same
  gene occur its often a . Pg. 394, 16-2
• Ex. An allele makes up ¼ of populations allele
  for a given trait. The relative frequency is
  25.
• In genetic terms, evolution is any change in the
  relative frequency of alleles (or traits) in a
  population.

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2 Main Sources of Genetic Variation

• Mutations
• Gene Shuffling
• Occurs during gamete (egg sperm) production
  results in many different combinations.
• Compare populations gene pool to a deck of cards.
  Shuffle you get a different hand each time but
  it never changes the of kings, aces, etc. The
  traits are still there, the of times they
  appear just changes.

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Polygenic Trait

• Can have many possible genotypes (gene
  combinations), producing many possible phenotypes
  (physical appearances).
• Controlled by 2 or more genes, each may have more
  than one allele (or form). Ex. Height.
• Bell Shaped Curve Pg. 396, 16-4
• How phenotypes are expressed.
• Most people are in the middle of the curve

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Polygenic Traits result in many different
phenotypes (appearances)
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Polygenic Trait Bell Shaped Curve
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16-2 Evolution as Genetic Change

• Natural Selection acts directly on phenotype
  (physical appearance). Ex. Lizard color. Pg.
  397, 16-5
• Natural selection on Polygenic Traits is more
  complicated because more than one gene works on
  the physical appearance..
• Directional
• Stabilizing
• Disruptive

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Directions, Disruptive Stabalizing Selection
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Directional Selection

• When individuals at one end of the bell-shaped
  curve have higher fitness than individuals near
  the middle or the other end of the curve.
• The curve shifts toward the higher fitness end.
• Ex.- birds with larger beaks will have higher
  fitness if a small-medium seed shortage occurs.
  Pg. 398, 16-6

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Stabilizing Selection

• When individuals near the middle of the curve
  have higher fitness than those on either end of
  the curve.
• This is where the average form of trait is.
• The curve narrows around the middle
• Ex.- a babies birth weight. Less wt., lower
  survival rate. Higher wt., difficult birth.
  Pg. 399, 16-7

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Disruptive Selection

• When individuals at the upper and lower ends of
  the curve have higher fitness than the
  individuals near the middle.
• The curve develops a peak at each end and a low
  point in the middle.
• Ex.- Medium bird seed has a shortage. Small
  large bird seed are abundant. Birds with small
  large beaks will have greater fitness. Pg. 399,
  16-8

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Genetic Drift- Contributes to Natural Selection

• Trait frequencies change.
• Occurs in small populations.
• Individuals with a particular trait leave more
  descendants than other individuals.
• Traits become more or less common by chance.
• The only similarity to natural selection is that
  they involve a change in a populations trait
  (allele) frequencies.

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Genetic Equilibrium

• A situation in which allele (or trait)
  frequencies of a population remain constant.
• 5 conditions required to maintain genetic
  equilibrium
• Random mating.
• Population must be very large.
• There can be no movement into or out of the
  population (migration).
• No mutations.
• No natural selection
• When all 5 are met, evolution will not occur.

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16-3 Process of Speciation

• Speciation- formation of new species
• For 1 species to evolve into 2 new species
• Gene pools of 2 populations must become
  separated.
• They must be reproductively isolated.
• Ex. finches on the Galapagos islands.

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Two forms of Speciation Gradualism Vs.
Punctuated Equilibrium
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Reproductive Isolation

• When members of 2 populations cannot interbreed
  produce fertile offspring.
• Behavioral- different courtship rituals.
• Ex. Songs.
• Geographical- populations are separated by
  geographic barriers. Ex. Mountains, rivers.
• Temporal- populations reproduce at different
  times. Ex. Pollination.

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Geographic Reproductive Isolation
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Speciation of Darwins Finches

• The species evolved on the Islands from a single
  species of founding birds.
• They traveled from mainland South America to one
  island to found a new population.
• They survived reproduced then crossed to a 2nd
  island.
• The became geographically isolated gene pool
  was no longer shared.
• Seed size on the island favored large beak birds.
• Large beak birds reproductively isolated
  evolved into a new species.

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Analogous Vs. Homologus Structues

• Analogous Sturctures Structures of different
  organisms that have similar functions. DO NOT
  RESULT from a shared common ancestor, but from
  similar environmental demands EVIDENCE OF
  NATURAL SELECTION EX bird wings insect wings.
• Homologous Structures anatomical structures or
  behavioral traits within different organisms
  which evolved from a structure or trait of their
  common ancestral organism. EVIDENCE OF COMMON
  ANCESTRY EX Bat Wing, Whale fin human arm

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Analogous Vs. Homologous