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Lecture 34

BIOL 1001 Lecture Notes - Lecture 34: Gradualism, Speciation, Punctuated Equilibrium


Department
Biology
Course Code
BIOL 1001
Professor
Tamara Kelly
Lecture
34

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March 6th Lecture Notes
Macroevolution
It’s the history of biodiversity-process, diversification, adaptations of species over a long
period
Use molecular, morphological analysis of fossil species to analyse macroevolution
Is Speciation Gradual or Sudden?
In in blue diagram there is gradual change b/t the
species where overtime the specie differentiate more
& more – gradualism
In pink diagram, it shows sudden change or burst in
phenotypic changes- called punctuated equilibrium
Punctuated equilibrium- evolution or sudden changes
or “bursts”
If evolution is gradual, we would see transitional
fossils. Transitional forms are preserved to give
records & provide evolutionary history
If evolution is quick, we expect big changes rapidly.
Transitional fossils are not preserved to show
intermediate states. No transitional forms remain as
evidence
Change in one gene can cause rapid evolution
What Drives Rapid Involutory Change?
Rapid evolution can occur due to environmental changed
Isolation of a population by a barrier- genetic drift
The large overall population remains the same. The isolated population experiences
rapid evolution. Pattern in the fossil records will record a large period of stasis
(constant) then a jump in a characteristic
Does Jump in Fossil Records= Evolutionary Burst?
Irregular preservation of transitional fossils can explain the jumps is transitional fossils
Transitional forms may not be efficiently preserved as fossils
Transitional forms may have only been present for a short period of time. There is a
chance that fossilization & preservation did not occur
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