Evolution

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Evolution

• Chapter 15

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What is Evolution?

• States that characteristics of plants and animals
  change over time
• The changes give them some type of advantage

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Charles Darwin English Scientist (1809-1882)

• Naturalist on the HMS Beagle for 5 years
• Found populations on the Galapagos Islands that
  were similar to mainland populations but had
  unique characteristics perfect for island life
• Finches beak type / body shape
• Tortoise shells

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What is Natural Selection?

• Natural selection is the mechanism for evolution
• Certain adaptations are selected FOR or AGAINST
  and over time adaptations that convey an
  advantage are found in the majority of the
  population

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From where do adaptations come?

• They are caused by random gene mutations which
  can be good, bad, or do nothing
• Good become more frequent
• Bad become less frequent

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Natural Selection

• 1. In a population, individuals have variation
• 2. Individuals with certain useful variations are
  more likely to survive and reproduce
• 3. Over time, offspring with those certain useful
  variations make up most of the population

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Natural Selection Fundamentals

1. Over-production - produce more offspring than
   will survive
2. Variation - Genetic
3. Competition - Compete for limited resources
4. Survival - Offspring with the most favorable
   traits survive and reproduce

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Patterns of Selection that emerge in evolution

• Stabilizing favors average individuals
• Directional favors one extreme or the other
• Disruptive favors both extremes

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Stabilizing Selection

• Average individuals have a selective advantage
• Reduces variation in a population
• Happens in stable environments

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Directional Selection

1. Favors one of the extreme variations of a trait
2. Can lead to rapid evolution of a population

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Disruptive Selection

• 1. Favors both extreme variations of a trait
• 2. Leads to evolution of two new species

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Two general ideas were proposed

• Lamarck said organisms can Acquire adaptations
  during their lifetime and pass them on to their
  children this is WRONG!
• Individuals do not evolve!
• Darwin said variation exists in any population
  and certain traits give an advantage. Those
  organisms with the traits produce more offspring
  and the traits slowly increase in frequency in a
  population!
• Populations evolve!

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Evolution 2 different ideas

• LaMarck (1809)

• 2. Darwin
• (1859)

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What evidence exists for evolution?

• Structural adaptations
• Physiological/metabolic adaptations
• Fossil record
• Anatomy
• Embryology
• DNA/RNA/Protein sequence comparisons

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Structural Adaptations

• - Physical adaptations that increase an
  organisms survival
• Examples
• Mimicry trying to look more dangerous
• Camouflage trying to blend in and hide

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2. Physiological/metabolic adaptations

• Changes in an organisms metabolic processes
• Examples
• Insect and weed resistance to pesticides/herbicide
  s
• Antibiotic resistance in bacteria

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3. Fossil Record

• Provide a record of early life and evolutionary
  history
• Examples
• Whales were once land mammals
• Horse evolution

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Whale evolution
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4. Anatomy

• Looking at the structural and functional
  similarity of a body feature
• Examples are homologous structures
• common bone structure found in all mammals
  indicate a common ancestor

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Anatomy cont.

• analogous structures are similar in function but
  not from a common ancestor like wings

• Vestigial structures do not have current function
  but were useful to an ancestor like appendix

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5. Embryology

• Similarities of young embryos suggest evolution
  from a distant, common ancestor
• Examples
• Fish, reptile, bird, and mammal embryo

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6. Biochemistry (molecular)

• Comparing DNA, RNA, and amino acids and looking
  for sequence similarities (more changes more
  distantly related)
• Examples
• Cytochrome C
• Hemoglobin

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What is a gene pool?

• All of a populations alleles and their frequency
• R 75
• r 25

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What is genetic equilibrium?

• When the frequency of alleles in the gene pool is
  not changing.
• No evolution or natural selection taking place.
• Year 1900 60 H and 40 h
• Year 2000 60 H and 40 h

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What is genetic drift?

• Genetic Drift is a change in the gene pool due to
  random sampling (by chance and unavoidable)
• Greatly affects small population

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What is the founder effect?

• Loss of genetic variation when a new population
  is founded with a small number of individuals
  (thus a same gene pool)

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What is Gene Flow?

• Gene flow is the transfer of genes from one
  population to another usually by migration into
  and out of a population

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What is Speciation?

• Speciation the process in which new species
  evolve from a common ancestor
• Species a group of organisms that interbreed
  and produce fertile offspring

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How does Speciation Happen?

• Three main ways species evolve
• Geographic Isolation
• 2. Reproductive Isolation
• 3. Change in number of chromosomes polyploidy

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Divergent Evolution

• When species that were once similar become more
  and more different.
• Adaptive Radiation
• one species evolves into an array of different
  species to fit environmental habitats

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2. Convergent Evolution

• When species that were unrelated evolve similar
  characteristics

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Gradualism vs. Punctuated Equilibrium

• Gradualism species originates by gradual rate of
  time
• Stable environment
• Punctuated Equilibrium speciation in short rapid
  bursts
• Catatrophic events that leave niches open
• Dinosaur extinction mammals

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