Evolution Intro

1
Evolution Intro
It is not the strongest of the species that
survives, nor the most intelligent that survives.
It is the one that is most adaptable to change.

• change over time. descent with modification.
  populations evolve, not individuals.

2
Charles Darwin

• (1809-1882) Englishman. Medical school dropout.
  Obsessed with nature. Aspiring clergyman.
  Married his cousin.
• The 5 year trip that changed Darwins life The
  Voyage of the HMS Beagle
• collected plants and animals. Noticed they were
  suited to diverse environments.
• Also found species resembled others around the
  world
• Influenced by geology (Lyell)
• Earth shaped by slow-acting forces that are still
  in work today
• The Galapagos. (finches)

3

• Alfred Russell Wallace. British naturalist that
  developed a theory very similar to Darwins. (His
  ideas were submitted for publication first)
• Darwin publishes On the Origin of Species in
  1859. His ideas convinced scientists of evolution
  to explain species diversity.
• Through time species accumulate differences as a
  result, descendants differ from their ancestors.
  In this way new species arise from existing ones.
• Natural Selection is the mechanism for evolution
• Descent with modification species share a common
  ancestor and diverged gradually over time

4
Darwins Ideas

• Descent with Modification.
• organisms share similar characteristics
  suggesting common ancestry.
• accumulate adaptations as environment changes,
  leading to different species
• gaps in record filled with fossil evidence
• Natural Selection.
• Variation in a population
• certain traits will give a higher probability of
  surviving to reproduce
• Species produce more offspring than survive.
• lead to accumulation of favorable traits in the
  population over generations
• causes organisms to become suited specifically to
  their environment
• May result in new species forming

5
Evidence

• Fossils
• evolutionary changes over time missing links
• compare current (extant) organisms with extinct
  ones
• Use geologic information and carbon dating to
  estimate age of fossils
• Homology (homologous structures)
• similar characteristics (but function
  differently) resulting from common ancestry
• forelimb of mammals
• vertebrate embryos
• vestigal structures leftover structures from
  an earlier ancestor (was important once upon a
  time)
• pelvic bones in a whale, snake, appendix

6
Evidence

• Biogeography
• geographic distribution of species
• influenced by continental drift (plate tectonics)
• Convergent evolution (similar environments yield
  similar anatomies)
• More evidence supporting organisms adapt to be
  best suited to their environment!
• Molecular Evidence
• DNA sequences similar from shared genes
• relationships between groups of organisms

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• microevolution change in allele frequencies in a
  population over generations (small scale)
• Result from accumulation of mutations
• Variation differences among individuals in a
  population
• only genetically determined phenotypes
  (characteristics) will be subject to natural
  selection
• without variation there is no evolution

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• Good Morning!!
• Have out your case study from yesterday. I will
  give you time to discuss with your group the
  answers you have.
• Behavior Labs should be done for tomorrow. See
  me if you have questions.
• We will prep our Natural Selection Lab tomorrow!

9
The White-Striped Clover

• Discuss with your group members your answers to
  this case study. Think specifically about the
  answers to the following.
• How does this case study illustrate the process
  of natural selection? What is the evidence that
  it occurred?Be able to justify your answers.
• What is selection pressure? How is it
  illustrated in each habitat? How does this affect
  the survival and reproduction of the clover?
• Thinking more broadlywhat influences natural
  selection in all organisms?

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• Selective pressures
• A phenotype (physical traits/behaviors) is
  selected for or against depending on the
  environment in which an organism lives
• Survival benefit or disadvantage
• Lead to differential survival and reproduction,
  driving natural selection
• Examples climate, food, predators, diseases,
  humans

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Influences on Variation

• Geography (geographic variation)
• differences in the genetic composition of
  populations of the same species
• Affected by environmental differences
• Mutations
• change in the nucleotide sequence of DNA
• only those present in gametes will be passed to
  offspring
• usually deleterious (harmful)very few are
  beneficial
• Chance/random events
• chromosomal shifts
• recombination during meiosis

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Influences on Natural Selection

• Competition Differential Survival
• Individuals with more favorable phenotypes will
  survive and reproducepassing on their traits to
  subsequent generations
• Genetic Variation and Mutation
• Diverse genes allow for survival in changing
  environments
• Variation results from mutation
• Environment
• Fluctuations in environment cause specific traits
  to be favored at certain times
• Human impacts
• Chance and Random Events
• ie. Earthquake splits population in two

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• Adaptation inherited characteristics of
  organisms that enhance their survival and
  reproduction in specific environments
• Natural Selection a process in which individuals
  that have certain inherited traits tend to
  survive and reproduce at higher rates than others
  because of those traits.
• acts on populations, not individuals
• only selects for heritable traits that exist
  within a population
• is specific to the environment in a particular
  time (flexible)
• consistently improves the match between organisms
  and their environment
• Fitness the number of surviving offspring in the
  next generation (measure of reproductive success)
• Artificial Selection human modified traits in a
  population due to selective breeding
  (agriculture, domestic animals)
• Convergent Evolution independent evolution of
  similar features in different lineages (analogous
  structures)