Endosymbiotic
Theory
The Endosymbiotic Theory

Review:
 What
is a theory?
 What is the difference between prokaryotic and
eukaryotic cells?

The endosymbiotic theory is the idea that a
long time ago, prokaryotic cells engulfed
other prokaryotic cells by endocytosis. This
resulted in the first eukaryotic cells.
 First
proposed by Lynn Margulis
 Explains the origin of eukaryotic cells
 Explains the origin of certain membrane-bound
organelles
What Exactly Happened?
Chloroplast
Heterotrophic
bacteria
Ancient Prokaryotes
Nuclear
envelope
evolving
Plants and
plant-like
protists
Photosynthetic
bacteria
Mitochondrion
Primitive Autotrophic
(Photosynthetic) Eukaryote
Animals, fungi, and
animal-like protists
Ancient Heterotrophic
Prokaryote
Primitive Heterotrophic
Eukaryote
Membrane-Bound Organelles

Mitochondria =
membrane-bound
organelle that produces
energy for the cell

Chloroplast =
membrane-bound
organelle that captures
sunlight and uses it to
make food for the cell
Evidence in support of the
endosymbiotic theory:

Similarities between mitochondria,
chloroplasts, & prokaryotes:
Circular DNA
2. Ribosomes
3. Binary fission
1.
Check these out:
Animation:
http://highered.mcgrawhill.com/sites/9834092339/student_view0/
chapter4/animation_-_endosymbiosis.html
Student form with fill-in’s:
Worksheet Notes\ENDOSYMBIOSIS
student fill-ins.docx