Download 1/23/02 Lecture Highlights – Evolution

1/23/02 Lecture Highlights – Evolution
In general sense: evolution is “change through time”
Outline
• Evolution of evolutionary thinking (history)
• Darwin’s theories of evolution
• Evidence for evolution
“The great chain of being”
• Aristotle’s “Scala Naturae”
• Species “fixed” – do not evolve
• Supernatural force
• Organized forms – lower
to higher (e.g., jellyfish to humans)
Erasmus Darwin – Charles’ grandfather
• One of earliest evolutionary thinkers
• Life came from “one living filament” (common ancestor)
• Temple of Nature (1802) (famous poem)
John Baptiste Lamarck
• Organisms change over time (evolve)
• Mechanism: principle of use/disuse
• Inheritance of acquired characters
Example – Giraffe
• As a species, giraffe was “created”
• Within a generation, stretched necks to reach juciest leaves
• Parents that stretched necks->offspring w/long necks
• Across generations – longer & longer necks
Charles Darwin – Voyage of the Beagle (5 year trip around earth)
• Galapagos finches –
• 13 species
– Some unique to individual islands
– Beaks for feeding on specialized foods
– Resembled mainland ancestor
Darwin’s theoriesOrganisms evolve over time- descent with modification (macroevolution) – accepted
The primary mechanism of evolutionary change is natural selection (microevolution) – not readily
accepted
So, Darwinean evolution is “descent with modification”; change in populations through time
“descent with modification”
Predictions:
• Relatedness of life forms
• Homology - similarities that link dissimilar life forms together – common descent (e.g,. bat wing,
human arm)
• Hierarchy: current (extant) forms can be grouped by decreasing similarity
• Change through time
• Direct Observation: change observed in natural populations
• Example: Peppered Moth in Great Britain
• Frequencies of light and dark moths changed with industrial revolution
• 20th Century – clean air standards -> less soot -> trend reversed
• We saw evolution happen!
•
•
Fossil Record: documents abundant change!
• Extinction
• Many, many, many fossils represent extinct organisms
• Transitional forms (e.g., Archeopteryx)
• Whale pelvis – vestigial trait: rudimentary (functionless) traits homologous to
fully functional traits in closely related species / whale fossils also represent
transition
• NYTimes 1-22-02 – Fish fossils used to date continental shifts – S America
from Antarctica ~20 MYA
• Succession
• Example: Horse
•
Life on earth is old
• Fossil dating
• Geological processes (e.g., erosion)