Transcript AP Biology (An Introduction)

Evolution of Prokaryotes to
Eukaryotes
Endosymbiosis
Prokaryote Summary
 Prokaryotes are about 1/10th of a eukaryote
 No true nuclei or membrane-bound organelles
 DNA is concentrated in the nucleoid region
 Simple genome compared to eukaryotes
 Prokaryotes have plasmids (extra-chromosomal DNA)
 Plasmids are circular pieces of DNA
 Used for generating genetic diversity in asexual
organisms (Binary Fission)
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Prokaryotic Summary (Page 2)
 Prokaryotes reproduce asexually by binary fission
 Continual synthesis of DNA
 Prokaryotes have a peptidoglycan cell wall
 Gram-Positive = simpler walls with more peptidoglycans
 Gram-Negative = more complex structure
 Pili used for adherence to each other or to surfaces
 Motile due to flagella
 different construction than eukaryotes – smaller, simpler
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What about the classification of…?
 Viruses?

Kingdom?
 Domain?
 Viroids?

Kingdom?
 Domain?
 Prions?

Kingdom?
 Domain?
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Questions
 Answer the following questions without using textbook
or any other resources:
a. If prokaryotes were the first cell type on earth and therefore the
ancestor to all eukaryotes, how did eukaryotes develop all of the
cellular components that they have?
b. Explain how the endomembrane system could have developed.
c. How could mitochondria and chloroplasts evolve?
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Endosymbiosis
 Eukaryotic cells originated from a symbiotic partnership of
prokaryotic cells
 Aerobic heterotrophs and photosynthetic prokaryotes =
chloroplasts
 Abundant evidence in the DNA + ribosomes of mitochondria
chloroplasts
 Multiple membranes in mitochondria, nucleus, +
chloroplasts
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Endosymbiosis (more detail)
 Certain organelles originated as free-living bacteria that
were taken inside another bacterial cell
 Endosymbionts – organisms that live inside another
organism, but have a symbiotic relationship
 Examples include rhizobium bacteria + legume roots
 Bacteria in ruminate stomachs (cows, etc)
 Mitochondria are bacterial endosymbionts (BE) that
were originally proteobacteria
 Chloroplasts are BE that were cyanobacteria
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Conclusion
 Prokaryotes evolved into eukaryotes by ____________
 Specifically, prokaryotes were engulfed by other
prokaryotes
 Why?
 Then, more engulfing occurred, and over enough time
we got eukaryotic cells
 This is the evolution of domains archaea + bacteria 
eukarya
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Domain Eukarya

Eukaryotic cells ONLY

Nucleus & Membrane
bound organelles

No peptidoglycan
(Is there a cell wall?)

Comprises which
kingdoms?
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Protista
 One of the most diverse divisions
 Not considered a kingdom anymore
 Most are unicellular or colonial
 Most are capable of asexual reproduction
 Some do both asexual & sexual reproduction
 Most protists are now categorized into other
“kingdoms”
 Largely due to DNA or Molecular Systematics
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