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news | march mammal madness!!!

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evolution | micro vs macro

Microevolution:

  • Small-scale changes
  • Few generations
  • Within a species
  • Directly observable

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Macroevolution:

  • Large-scale changes
  • Long period of time
  • Extended microevolution
  • Fossil record

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the theory of evolution | making predictions

"To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree." (Darwin 1859, from On the Origin of Species)

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the theory of evolution | darwin (19thcen)

If evolution is a theory, then we can find ways of testing it

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Darwin’s 5 Theories:

  • Perpetual Change
  • Common Descent
  • Multiplication of Species
  • Gradualism
  • Natural Selection

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darwinism | perpetual change

  • Time is linear
  • Fossils = remnants (with bias) of the past
    • index fossils
  • Radioactive decay
  • Trends (e.g. horses)

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darwinism | index fossils

  • Wide geographic distribution
  • Existed for a brief period so any rock layer containing that fossil can be linked to a specific geologic time.
  • Example above: The columns represent rocks from different geographic regions. Each layer within a column represents a brief period of time.

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darwinism | index fossils

  • A: Trilobite
  • B: Billingsella corrugata (bivalve)
  • C. Ammonite (nautilus)
  • D. Nerinea (gastropod)

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darwinism | perpetual change

  • Fossil bias

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darwinism | common descent

  • Phylogeny (one evolutionary tree)
  • Comparative Anatomy: Homology
  • Vestigial organs
  • Nested hierarchy
  • Paedomorphosis
  • Ontogeny Recapitulates Phylogeny (not true, but sort of)

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darwinism | common descent

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darwinism | common descent

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darwinism | common descent

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axolotl & mudpuppies

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different growth rates

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stunted growth rates

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darwinism | multiplication of species

Ancestral species split into new groups

  • Selective forces
    • Winter, Disturbance, Predators
    • Create barriers
  • Selection types
  • Founder events (MV deaf)
  • Adaptive radiation
  • Sympatric vs allopatric

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darwinism | multiplication of species

Ancestral species split into new groups

  • Selective forces (e.g. clines)

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darwinism | multiplication of species

  • Adaptive radiation

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darwinism | multiplication of species

  • Founder events (MV deaf)
  • Rotifers
  • Genetic bottleneck = limitation

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darwinism | multiplication of species

  • Allopatry = barriers (e.g. clownfish)
  • Sympatry = behaviors (e.g. spadefoot)

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darwinism | gradualism vs punctuated equilibrium

"... it is probable that the periods, during which each [species] underwent modification, though many and long as measured by years, have been short in comparison with the periods during which each remained in an unchanged condition."

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Darwin in Origin of Species

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We [Eldredge & Gould] argued that two outstanding facts of the fossil record -- geologically "sudden" origin of new species and failure to change thereafter (stasis) -- reflect the predictions of evolutionary theory, not the imperfections of the fossil record. In most theories, small isolated populations are the source of new species, and the process of speciation takes thousands or tens of thousands of years. This amount of time, so long when measured against our lives, is a geological microsecond . . .

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Since we proposed punctuated equilibria to explain trends, it is infuriating to be quoted again and again by creationists -- whether through design or stupidity, I do not know -- as admitting that the fossil record includes no transitional forms. Transitional forms are generally lacking at the species level, but they are abundant between larger groups.

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Gould in Hens Teeth & Horse Feathers

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darwinism | gradualism

  • Gradualism
  • Phyletic Gradualism vs Punctuated Gradualism
  • Population gradualism (elephant ears)

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darwinism | gradualism

  • Phenotypic gradualism
  • Population gradualism (migration)

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darwinism | gradualism

  • ​

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darwinism | gradualism (peppered moth)

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Natural Selection

  1. Individuals within populations are variable
  2. Variation is heritable
  3. Organisms differ in their ability to survive and reproduce
  4. Survival & reproduction are non-random

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Darwin’s explanatory model of evo by nat sel

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natural selection | Darwin’s elephants

Daughters/Elephant

Pop’n after 500 yrs

# F/M

0

0

-

1

22

.22

2

64,771

.89

3

864,333

2.32

4

7,315,931

5.53

5

13,368, 523

15.81

6

0

-

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natural selection | Darwin’s elephants

What does natural selection shape?

  • behavior
  • biochemistry
  • morphology
  • possibility

What it does not shape or explain?

  • choice? free will?
  • expression of possibility (e.g. heritability)

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darwinism | biogeography

  • Alfred Russel Wallace (1823-1913)
    • A people’s naturalist
    • Father of Biogeography
    • Natural selection
      • Favored environment as a selective force over competition (Darwinism)

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life history | biogeography

What an organism needs from start to finish:

  • Reproductive capacity
  • Parental investment
  • Metamorphosis, growth rate
  • Dealing with prey through different life stages
  • Dealing with competition from other individuals/species
  • Dealing with predators
  • Social interactions, culture, learning
  • Mating strategies, age of maturity, etc
  • Longevity