Cellular Evolution Symbiotic Theory First cell = prokaryote (~3.5 billion years ago) Next cell type = eukaryote (~1.5 billion) Prokaryotes began to change when there was limited resources (food). Prokaryotes evolved into eukaryotes. But how? Symbiotic Theory Aka: Big Gulp Theory Symbiosis = an association between 2 or more species

Cellular Evolution Scenario explaining the Symbiotic Theory: Prokaryote (A) can’t make food but is large Prokaryote (B) can make food but is small and can’t protect itself Prokaryote (B) is taken into prokaryote (A) starts to live inside of it Prokaryote (A) protects (B) and (B) makes food for (A)

Cellular Evolution 5. Prokaryotes (A & B) can survive better than before and better than other cells 6. Over millions of years, prokaryote (B) becomes a permanent part of prokaryote (A). 7. Prokaryote (B) will no longer need certain structures because (A) will do those functions for (B). Ex: structures for moving, commanding cell functions, etc. 8. Prokaryote (A) now has a membrane-bound organelle and now becomes a eukaryote

Cellular Evolution Ex: Elodea After eukaryotic cells formed, simple Eukaryotes evolved into colonial organisms- genetically identical cells living together in group Ex: Volvox Colonial organisms evolved into multi-cellular organisms when the cells in the colonial organisms became different Ex: Elodea