1. 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

2. 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)

3. 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

4. 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