Evolution “into” the “protista” Modern Protista represent the first eukaryotes First eukaryotes evolved from prokaryote ancestors Modern Prokaryotes represent those ancestors How?

Evolution of First Eukaryote(s) Forces leading to eukaryote *Increases in size *Increases in complexity Mechanisms *Infolding of cell membrane *Serial endosymbiosis of membrane-bound organelles *Combination of the two

Evolution of multicellularity Multicellularity evolved several times 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 All cells the same All cells the same Little or no differentiation in function Little or no differentiation in function Cooperation Cooperation *Volvox *Filaments are a kind of colony May provide “buoyancy” May provide “buoyancy”

Multicellularity - complex bodies Differentiation of tissues, organs Differentiation of tissues, organs *Allows larger bodies *Division of labor *Requires more complex development Several times Several times *Seaweeds – 3 lines, one to plants *Fungi *Animals Kelp forest

Evolution “out of” the “protista” 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 – mya (in sea, later joined plants on land) *Animals – mya (in sea) *Plants – 400 mya (on land)