Transcript Protista - Evolution

Evolution “into” the “protista”
• Modern Protista represent the first
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eukaryotes
First eukaryotes evolved from prokaryote
ancestors
Modern Prokaryotes represent those
ancestors
How?
Biology 102, Winter '04
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Phylogenetic tree of the Kingdoms of Life
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Wall-less Bacteria
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Bacteria
Universal ancestor (s)
first cell(s?)
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Early Protists
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Eukaryotic
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Evolution of First Eukaryote(s)
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Forces leading to eukaryote
* Increases in size
* Increases in complexity
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Mechanisms
* Infolding of cell membrane
* Serial endosymbiosis of
membrane-bound organelles
* Combination of the two
Evolution of multicellularity
• Multicellularity evolved several times
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among the “protista”
Complex, differentiated bodies evolved
fewer times among the “protista”
* Brown, green and red seaweeds
* Slime molds (to be covered in the future)
Multicellularity colonies
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All cells the same
Little or no differentiation in function
Cooperation
* Volvox
* Filaments are a kind of colony
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May provide “buoyancy”
Multicellularity complex bodies
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Differentiation of tissues, organs
* Allows larger bodies
* Division of labor
* Requires more complex development
Several times
* Seaweeds – 3 lines, one to plants
* Fungi
* Animals
Kelp forest
Evolution “out of” the “protista”
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Three exclusively multicellular kingdoms evolved
from protistan lines (some multicellular, some not)
* Plants (from green algae)
* Animals (from flagellated protozoa – choanoflagellates)
* Fungi (from flagellated protozoa – choanoflagellates)
When? Just before the Cambrian period
* Fungi – 1100-800 mya (in sea, later joined plants on
land)
* Animals – 1100-800 mya (in sea)
* Plants – 400 mya (on land)