Concepts of Evolution

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Concepts of Evolution
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Charles Darwin

• Jean Baptist Lamark suggested the theory of the
  inheritance of acquired characteristics
• Charles Darwin born 1809
• Sailed around the world on the HMS Beagle in
  December 1831 at 22 years of age
• Ventured to Galapagos Islands noticed that
  fossils in South America resembled modern day
  species

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• The voyage of the Beagle

Great Britain
Europe
NorthAmerica
PacificOcean
AtlanticOcean
Africa
GalápagosIslands
Equator
SouthAmerica
Australia
Andes
Cape ofGood Hope
Tasmania
Cape Horn
NewZealand
Tierra del Fuego
Figure 13.1B
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Charles Darwin

• While on the voyage, read Principles of Geology
  which suggested that natural forces change
  environments.
• Returned five years later
• 1840, composed a long essay on the theory of
  evolution. Did not publish due to fear of
  criticism
• 1859, published On the Origin of Species which
  was based on fossils indicating descent with
  modification

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Charles Darwin

• Thomas Malthus (1798) proposed that disease,
  famine, war, etc. were inescapable consequences
  of human populations potential to grow faster
  than resources would allow.
• Darwin coined the term Natural Selection
  results in favored traits being represented more
  and more and unfavored traits represented less
  and less.
• Conclusions 1) Diverse forms from common
  ancestry 2) Natural Selection

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Natural Selection

• Three general outcomes from Natural Selection
• Stabilizing selection intermediate variants
  (most common)
• Directional selection shifts overall makeup of
  individuals to one extreme (environment is one
  drastic type)
• Diversifying selection both extremes visible
  (drastic environments usually separated)

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Fossils

• Petrification minerals from water seep into
  tissues of dead organisms and replace organic
  matter
• Most fossils are formed by leaving an empty mold
  that is later filled by minerals
• Fossils can occur that will not allow bacteria or
  fungi to form. When this happens, organic
  material is preserved (fossil resin)
• Paleontologist scientist who studies fossils

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Evidence Validates Evolution

• Biogeography geographic distribution
• Galapagos Islands is a tropical island yet the
  inhabitants resembled South America and not the
  typical species found on a tropical island.
• Comparative Anatomy comparision of body
  structures. These features have different
  functions but structurally similiar.

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Evidence Validates Evolution

• Molecular Biology the study of molecular basis
  of genes. Related species have homologous DNA.

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Hardy-Weinberg Equation

• Population group of individuals of same
  species, living in same place at the same time
• Population genetics science of genetic change
  in a population
• Gene pool total collection of genes in a
  population at one time. Alleles may be
  homozygous or heterozygous.

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Recombinationof alleles fromparent generation
W sperm p 0.8
W egg p 0.8
SPERM
EGGS
WW p2 0.64
w sperm q 0.2
w egg q 0.2
WW qp 0.16
Ww pq 0.16
ww q2 0.04
Next generation
Genotype frequencies
0.64 WW
0.32 Ww
0.04 ww
Allele frequencies
0.8 W
0.2 w
Figure 13.8C
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Hardy-Weinberg Equation

• Microevolution change in frequency of alleles
  in a populations gene pool
• Hardy-Weinberg Equation explains the gene
  frequency of alleles in a population that is not
  evolving
• P 2 2pq q 2 1

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Hardy-Weinberg Equation

• P 2 2pq q 2 1
• p frequency of dominant allele
• q frequency of recessive allele
• (remember, frequencies are determined by the
  total number of instantcies calculated)

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Hardy-Weinberg Equation

• (Example) Blue-Footed Boobies 500 total
• 320 boobies WW (nonwebbed)
• 20 boobies ww (webbed)
• 160 boobies Ww (non-webbed)
• Calculation of Genotypic Frequencies
• WW 320/500 0.64
• Ww 160/500 0.32
• ww 20/500 .04

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• We can follow alleles in a population to observe
  if Hardy-Weinberg equilibrium exists

Phenotypes
Genotypes
WW
Ww
ww
Number of animals(total 500)
320
160
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Genotype frequencies
320/500 0.64
160/500 0.32
20/500 0.04
640 W
160 W 160 w
40 w
Number of allelesin gene pool(total 1,000)
800/1,000 0.8 W
200/1,000 0.2 w
Allele frequencies
Figure 13.8B
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Hardy-Weinberg Equation

• Calculation of Allele frequency in a population
• 1000 genes in the pool (500 x 2)
• (W) 320 from (WW) x 2 640 160 from (Ww)
  800 W alleles (p)
• (w) 20 from (ww) x 2 40 160 from (Ww)
  200 w alleles (q)

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Hardy-Weinberg Equation

• Calculation of genotypic frequency of the next
  generation
• What is the probability of producing an
  offspring of genotype WW?
• p 2 or 0.8 x 0.8 0.64
• What is the probability of producing an
  offspring of genotype ww?
• q 2 or 0.2 x 0.2 0.04

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Hardy-Weinberg Equation

• Calculation of genotypic frequency of the next
  generation
• What is the probability of producing an
  offspring with the genotype Ww?
• 2pq 2 (0.8 x 0.2) 0.32

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Causes of Microevolution

• Genetic Drift change in gene pool of a small
  population due to change
• Caused by chance
• Natural Selection NOT involved
• Two types of genetic drift are Bottleneck effect
  and Founder effect ( End result no variation in
  alleles)
• Bottleneck genetic drift resulting from an
  event that drastically reduces population size
  from (flood, earthquake, etc)
• Founder single animal developing a new
  population

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