EVOLUTION

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What is Evolution?

• Change over time
• The theory of evolution proposes that modern
  forms of life have descended from earlier forms
  of life and changed as they descended.
• What caused the changes or differences in
  traits?
• MUTATIONS!!
• Can we control this?

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Why is the Theory of Evolution so Controversial?

• People have varying beliefs on the origin of life
  due to religion.
• Biological evolution does not study the origin of
  life. It only studies the changes in life forms
  since their origin.

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Mechanisms that drive evolution?

• Mutation random changes in the DNA
• Natural Selection
• Gene Flow movement of alleles into or out of a
  population
• Genetic drift changes in the alleles of a
  population due to random events (i.e. natural
  disaster.
• Important terms to know
• adaptation- A characteristic that increases
  fitness.
• fitness- The ability to survive and reproduce.

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What is natural selection?

• A theory introduced by Charles Darwin
• A process that increases or decreases the
  presence of a trait depending on the traits
  ability to keep the organism alive and
  reproducing.
• 3 conditions must be met for natural selection to
  occur
• Variation in characteristics (due to mutations)
• Differences in fitness
• Heritability (can be passed down to offspring) of
  the characteristic

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Examples of Natural Selection

• Galapagos finches different beaks
• Male peacocks varying brightness in their
  feathers
• Giraffes varying neck length
• Sharks white on the underside and blue/gray on
  top
• Humans varying resistance to malaria
• Bacteria antibiotic resistance

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Natural Selection Lab
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Natural Selection Lab
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How do we know if evolution has occurred?

• The Hardy-Weinberg Principle calculates genetic
  variety in a population. If the genetic variety
  remains constant from one generation to the next,
  it is said to be in Hardy-Weinberg equilibrium
  (not evolving).
• The H-W equation is
• p2 2pq q2 1 (or 100)
• p q 1

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Hardy-Weinberg continued

• q2 the frequency of homozygous recessive
  individuals.
• 2pq the frequency of heterozygous individuals.
• p2 the frequency of homozygous dominant
  individuals.
• p the frequency of the dominant allele.
• q the frequency of the recessive allele.

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Hardy-Weinberg continued

• Five conditions must be met for a population to
  remain in H-W equilibrium
• Random mating
• No movement of members into or out of the
  population
• No natural selection
• No mutations
• Population must be large

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• Hardy-Weinberg Practice
• Brown hair (B) is dominant to blonde hair (b). If
  there are 168 brown-haired people in a population
  of 200, what are the frequencies of homozygous
  dominant, homozygous recessive and heterozygous
  individuals?

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Hardy-Weinberg Goldfish Lab
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Another H-W problem

• Tongue rolling is a dominant trait. Who in the
  class is homozygous recessive (tt) and cannot
  roll his/her tongue? What are the p2, 2pq and q2
  values for the class?

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Cladogram

• Evolutionary relatedness between organisms can be
  demonstrated on a diagram called a cladogram.
• Organisms with similar characteristics are placed
  more closely on the diagram because they are
  thought to have evolved more closely to one
  another.
• As an organism evolves, there is a new branch on
  the cladogram.
• Characteristics that evolve between species are
  called derived characters.

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One more H-W problem

• Calculate the p2, 2pq and q2 values when 14 out
  of 113 members of a population have the recessive
  trait for left handedness.

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Evidence of Common Ancestry

• The theory of evolution states that all living
  things have descended from another life form,
  just as you have descended from your parents and
  they descended from their parents.
• The evidence that supports this theory includes
• Fossils
• DNA
• Embryo structure
• Comparative anatomy

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Evidence of Common Ancestry- Fossil Record

• Layers of rock contain fossils
• new layers cover older ones
• creates a fossil record over time
• fossils show a series of organisms that have
  lived on Earth

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Evolution from sea to land

• Fossils are also evidence of transitional (in
  between) forms.
• In 2006, there was the fossil discovery of the
  missing link between sea and land animals
• 4 limbs
• called Tiktaalik

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Evidence of Common Ancestry- Comparative Anatomy
Animals with different structures on the surface
But when you look under the skin
It tells an evolutionary story of common ancestors
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Compare the bones

• Limbs of different animals that perform different
  functions are built with the same bone structure

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Homologous structures

• Structures that come from the same origin
• homo same
• logous information
• Forelimbs of humans, cats, whales, bats are
  homologous structures.
• same internal structure but different functions
• evidence of common ancestor
• The greater the of homologous structures
  between organisms, the more closely related they
  are.

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But dont be fooled by these

• Analogous structures
• look similar on the outside
• have the same function
• different internal structure
• This means they do not have a close evolutionary
  relationship

How is a birdlike a bug?
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Vestigial organs

• Structures of modern animals that have no
  function
• evolutionists believe that these were functional
  in ancestors
• evidence of change over time
• some snakes whales have pelvis bones leg
  bones of walking ancestors
• eyes on blind cave fish
• human tail bone

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Vestigial organs

• Hind leg bones on whale fossils

Why would whales have pelvis leg bones if they
were always sea creatures?
Because they used to walk on land!
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Evidence of Common Ancestry- Embryology

• Development of an embryo tells an evolutionary
  story
• The greater the of similar structures during
  embryo development, the more closely related they
  are.

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Evidence of Common Ancestry-Biochemistry

• Comparing DNA protein structure
• Every living thing uses the same genetic code!

• The fewer the number of differences in the amino
  acid sequence of common proteins, the more
  closely related organisms are.

number of amino acids different from human
hemoglobin
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  Horse Chicken Tuna Frog Shark Turtle Monkey Rabbit
Human 6 6 9 8   14 8 1 4
Rabbit 5   5   9 6 12 7 5 X
Monkey 7   8 10 8 13 9 X X
Turtle 7   2 9 5 12 X X X
Shark 11   12 12 12 X X X X
Frog 8   3 8 X X X X X
Tuna 11   7 X X X X X X
Chicken 7   X X X X X X X

• What 2 organisms on the chart above are the most
  alike in terms of DNA?
• What 2 organisms are the least alike?
• What is the turtles closest relative? Why does
  this data make sense?

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What data from whole genome sequencing can tell
us about evolution of humans
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Example the Evolutionary Hypothesis of Common
Ancestry Chromosome Numbers in the great
apes human (Homo) 46chimpanzee
(Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48
Testable prediction If these organisms share a
common ancestor, that ancestor had either 48
chromosomes (24 pairs) or 46 (23 pairs).
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Ancestral Chromosomes
Chromosome Numbers in the great apes
(Hominidae) human (Homo) 46chimpanzee
(Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48
Centromere
Telomere
Testable prediction Common ancestor had 48
chromosomes (24 pairs) and humans carry a fused
chromosome or ancestor had 23 pairs, and apes
carry a split chromosome.
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Human Chromosome 2 shows the exact point at
which this fusion took place
Chromosome 2 is unique to the human lineage of
evolution, having emerged as a result of
head-to-head fusion of two acrocentric
chromosomes that remained separate in other
primates. The precise fusion site has been
located in 2q132q14.1 (ref. 2 hg 16114455823
114455838), where our analysis confirmed the
presence of multiple subtelomeric duplications to
chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22
(Fig. 3 Supplementary Fig. 3a, region A). During
the formation of human chromosome 2, one of the
two centromeres became inactivated (2q21, which
corresponds to the centromere from chimp
chromosome 13) and the centromeric structure
quickly deterioriated (42).
Homo sapiens
Inactivated centromere
Telomere sequences
Chr 2
Hillier et al (2005) Generation and Annotation
of the DNA sequences of human chromosomes 2 and
4, Nature 434 724 731.
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Building family trees

• Evolution evidence can be used to create family
  trees. Closely related species are branches on
  the tree coming from a common ancestor

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Human Impact on Evolution- Selective Breeding
Humans create the change over time
descendants of the wolf
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Artificial Selection

• and the examples keep coming!

I liked breeding pigeons!
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Insecticide resistance

• Human activities like spraying crop fields with
  insecticides leads to
• The survival of insects that are resistant to the
  insecticide
• Resistant survivors reproduce
• Resistance is inherited
• Insecticide becomes less less effective

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