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Evolution. Schoonover. “Nothing in biology makes sense except in the light of evolution .” – Theodosius Dobzhansky

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“Nothing in biology makes sense except in the light of evolution.”

– Theodosius Dobzhansky

  • “Most species do their own evolving, making it up as they go along, which is the way Nature intended. And this is all very natural and organic and in tune with the mysterious cycles of the cosmos…which believes that there’s nothing like millions of years of really frustrating trial and error to give a species moral fiber and…in some cases…a backbone.”

- Terry Pratchett



Developing a Theory

  • The gradual change in organisms over time.
a theory in science is
A theory (in science) is…
  • …created when a hypothesis or group of hypotheses has been supported with repeated testing.
  • If enough evidence accumulates to support a hypothesis, it moves to the next step—known as a theory—in the scientific method and becomes accepted as a valid explanation of a phenomenon.
charles darwin
Charles Darwin
  • The Father of Evolution
  • Life/Journey
    • Doctor? No, ecologist & naturalist
  • Sailed the world on a ship called the H.M.S. Beagle
    • Age 24-29
    • Took samples of species and detailed observations…
    • Visited Galapagos Islands
      • Found unique organisms
      • Studied many species, ex. finches, tortoises, iguanas, etc.
        • Noticed adaptations for food, mates, habitats…to survive
charles darwin cont
Charles Darwin, cont…
  • Raised and bred exotic pigeons
    • Artificial selection – breeders select parents with desirable traits so those traits are passed on
      • Ex today – Dogs, horses, cows, crops, etc.
  • With Lamarck, thought individuals adapt to environments and species change over time
  • Wrote books
    • On the Origin of Species
    • The Descent of Man
    • Selection in Relation to Sex
    • The Expression of the Emotions in Man and Animals
quick quiz 1
Quick Quiz #1
  • What is evolution?
    • A gradual change in species over time
  • Who is the ‘father of evolution’?
    • Charles Darwin
  • What is artificial selection?
    • Breeders selecting for desirable traits


Applying Darwin’s Ideas

natural selection
Natural Selection
  • The process where individuals with advantageous traits (for their environment) survive and reproduce
    • Those traits seen more frequently in future generations
    • Eg. Speed, ability to fly further distances, ability to adapt, resistance to insecticide, etc.
  • Requirements for natural selection:

1. Overpopulation

2. Variation of traits

3. Selection of mates

4. Adaptation

natural selection on traits
Natural Selection on Traits…
  • Stabilizing
    • Pressure from two directions makes average trait most fit (outliers least fit)
  • Disruptive
    • Pressure on the average trait results in divergence (outliers most fit)
  • Directional
    • Pressure from one direction alters frequency of trait
  • Does natural selection act on the phenotype or genotype of a species?
an adaptation is
An adaptation is…
  • …a change in behavior, physiology, and/or structure of an organism or species to become more suited to an environment…gradual
    • Eg. Dolphin behavior video
quick quiz 2
Quick Quiz #2
  • What is natural selection?
    • When individuals with advantageous traits survive and reproduce.
  • What are the three ways natural selection affects traits?
    • Directional, stabilizing, & disruptive
  • What is an adaptation?
    • A change in behavior, physiology, or structure that makes a species more suited to an environment


Evidence for Evolution

  • World distribution of organisms
  • Shows similarities among species living on different continents
  • Trait adapted to similar function but with a different origin
early development
Early Development…
  • Embryos of many vertebrates are very similar
    • Similar stages of development
comparative morphology
Comparative Morphology…
  • Homologous Body Structures:
    • Limbs come from the same embryonic tissue and at same basic location
    • Why use the same skeletal plan for these very different appendages?
  • Record shows biodiversity
  • Shows changes in species over time…stages of development
  • Law of Superposition…
darwin s finches
Darwin’s Finches…
  • 14 species of finches
    • Different niches
    • Different food sources
  • What does this show?

similar dna
Similar DNA…
  • Biochemistry
  • Commonality of genetic code, similar amino acids
similar dna cont
Similar DNA, cont…
  • Why should different organisms have so many similar genes?
  • Called a cladogram

can we see evolution
Can we see evolution…?
  • We can see the effects of evolution, artificial selection
  • Tuberculosis video…
darwin was not alone
Darwin was not alone…

Charles Lyell – uniformatarianism


Georges Cuvier – species extinction


darwin was not alone1
Darwin was not alone…

Thomas Malthus – struggle for existence


Jean Baptiste de Lamarck – evolution by acquired characteristics


and the less well known
And the less well known…
  • Alfred Russel Wallace
    • Drew same conclusions as Darwin
    • Not an easy journey…
      • 11 years up in smoke (Amazon River Basin)
      • 8 more years of work (Malay Archipelago)
  • Later worked jointly with Darwin
darwin s theory a summary
Darwin’s Theory…a summary
  • Uncontrolled populations grow exponentially
  • Limited resources = survival of the fittest
  • No two individuals are exactly the same
  • If the inherited traits allow one to be “better” they will survive and pass on those traits
  • As the fittest survive, the population’s traits change over time
quick quiz 3
Quick Quiz #3
  • List five reasons evolution is a supported theory.
    • Biogeography
    • Convergence
    • Early development
    • Homologous structures
    • Fossils
    • Darwin’s finches (adaptive radiation)
    • Similar DNA (biochemistry)
    • Other scientists came up with similar hypotheses as Darwin…he wasn’t alone


Beyond Darwinian Theory

microevolution is
Microevolution is…
  • Changes in the genes of populations
  • Small scale (generation to generation)
how does microevo happen
How does Microevo. Happen?
  • Natural Selection
  • Mate Choice
  • Mutations in DNA
  • Gene Shuffling
    • Random mixing of genes during sexual reproduction
  • Gene Flow (not completely random)
    • Immigration
    • Emigration
    • Migration
  • Genetic Drift (random)
genetic drift is
Genetic Drift is…
  • Individuals with a particular trait have more descendants just by random chance
  • Random changes of allele (trait) frequency in a population
    • Eg. Wildfire, disease, earthquake, etc.
    • Can lead to a ‘bottleneck effect’
  • Variation within a species helps insure that some will survive major changes in the environment and continue the species
  • Variation of species is vital for the continuation of life.
  • For life to continue we need ___________________.
macroevolution is
Macroevolution is…
  • The appearance of new species over a long period of time
types of macroevolution
Types of Macroevolution…
  • Convergent evolution – similar environment will cause similar adaptations
    • Ex: armadillo and anteater – sticky tongues and foreclaws
    • Ex2: whale and shark– fins, sleek body, tails, etc.
  • Divergent evolution – different environment will cause species to change over time

  • Coevolution – organisms in same environment “evolve together”
    • Ex: Ant – Acacia Plant (mutualism)
types of macroevo cont
Types of Macroevo., cont…
  • Adaptive Radiation – new species enters an environment with few species in it
    • Ex: Darwin’s finches – came from one species and changed to fit their niche
  • Extinction – species dying out when traits are not beneficial for changing environment and species cannot adapt
  • Gradualism – small changes over time will create new species
  • Punctuated Equilibrium – Environmental pressures are great, forcing a new species to arise in short time
speciation is
Speciation is…
  • The formation of new species that cannot or will not interbreed with the original species.
  • Types:
    • Reproductive Isolation: cannot interbreed due to physical changes
    • Behavioral Isolation: can interbreed but won’t because of differences in courtship rituals or other types of behavior
      • Eg. Birds of Paradise
    • Geographic Isolation: cannot interbreed because of geographic barriers such as rivers, mountains, etc.
    • Temporal Isolation: do not reproduce because species reproduce at different times of the year
quick quiz 4
Quick Quiz #4
  • What is microevolution?
    • Small changes in the genes/traits of populations
  • How does microevolution happen?
    • Natural selection, Mate choice, Mutations in DNA, Gene shuffling, Gene flow, & Genetic drift
  • Genetic drift is _______ and can lead to the _______ effect (which results in less genetic diversity).
    • Random, bottleneck
  • What is macroevolution?
    • The appearance of new species over a long period of time
    • Know types of evolution: Convergent, divergent, co-, adaptive radiation, gradualism, punctuated equilibrium
  • What is speciation?
    • The formation of new species that cannot or will not interbreed with the original species
  • What if a giraffe (over millions of years) started evolving into an animal more like a seal?
    • Why might this happen?
    • What might be the intermediate species?
    • Relate this to the following terms:
      • Microevolution, macroevolution, mutation, gene shuffling, gene flow, genetic drift, trait, predation, limited resources, habitat, divergent evolution, convergent evolution, homologous structures, speciation, survival of the fittest, etc.