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Proterozoic Eon lecture notes.doc

Course Code
BIO 1130
Jon Houseman

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Proterozoic Eon
Slide 2:
Proterozoic Eon
-oxygen atmosphere makes appearance at the end of the Archean eon
-anaerobic bacteria go to places where there is no oxygen (i.e.: depths of the ocean) since
the world has started to become filled with oxygen
-aerobic bacteria make their appearance
-appearance of single-celled eukaryotes
-no progression beyond single-celled eukaryote organisms during the Proterozoic eon
-world contains aerobic bacteria, anaerobic bacteria, and single-celled eukaryote organisms
-perfection in single-celled organisms
-no jump to multi-cellularity
Slide 3:
-prokaryotes are divided into archea and bacteria
-single-celled eukaryotes stem from the archea
-archea are closely related to eukarya and distantly related to bacteria
Slide 4:
-refer to table 21.1
Cell Wall
-important for maintaining cellular integrity
-may have evolved once and every organism has inherited this type of cell wall
-analogous and convergent evolution for cell walls
-doesn't tell us about the evolution of these groups
Plasma Membrane
-unbranched, zig-zag pattern for fatty acid chains in eubacteria and eukarya
-branched, non-zig-zag pattern for the plasma membrane in archea
-convergent evolution for fatty acids
-simple chains arose first (Occam's razor- simple to complex)
-eukaryotes and bacteria arose at the same time with the unique membrane system which
diverged off to create the archea
-this theory is inverted compared to the generally accepted theory*
-archea and bacteria flagella spin with a motor; eukarya motor beats
-independently evolved event and is not helpful
-if there has been a modification it would have been shared by all descendents
-eubacteria appear to be most primitive based on this

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Histone Proteins
-mechanism for wrapping DNA and protection
-in bacteria DNA folds on itself to create the structure that protects and stabilizes the DNA
(no proteins involved)
-eukarya and archea are using the same type of proteins to package and stabilize DNA
within the cell
-the archea are very similar to the eukarya
-when we look at the evolution of these 3 groups, the bacteria diverge very early on with
the RNA polymerase and DNA folding and these are unifying traits for eukarya and archea
-when the first single-celled organism arose, it resembled bacteria and over time, it
specialized (improved RNA polymerase, DNA protection, etc. )
-the phylogeny shows that bacteria are primitive compared to the archea which share
advanced traits with eukarya (the difference is that eukarya will put their genetic material
in a membrane)
Slide 5:
Nuclear Envelope
-for a cell, life's processes occur on surfaces
-if there is a lot of activity in the cell, you need to increase the amount of surface area in
order to supply the cell
-invagination / invaginating membrane allows for increased surface area and this ends up
surrounding nuclear material (the origins of the nucleus)
-2 plasma membranes surrounding the nucleus (nuclear envelope)
-inside the nucleus there is biochemical optimization for DNA replication and delivery
-we have separated the nuclear environment from the cytoplasmic environment
-in the nucleus DNA and RNA is created
-in the cytoplasm, translation can occur
-compartmentalizing processes allows for efficiency
-nuclear pores allows for communication between the nucleus and the cytoplasm
-the same infolding creates the endoplasmic reticulum
Slide 6:
Endosymbiosis of Bacterial Cells
-origins of the mitochondria
-partitioning of energy system
-at some point in time, a large bacterial cell engulfed a bacterium that had the electron
transport chain in it and when it engulfed it (normal way of feeding), it kept some plasma

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membrane around the bacterium and the bacterium creates ATP as the cell feeds pyruvate
to the bacterium
-symbiotic relationship
-a partitioning of the energy system has occurred and the bacterium is doing the
majority of the work
-this was a tremendously successful event
-the cell that first did this multiplied successfully and creates the best adaptive
cells and it fills the oceans
-the mitochondria has many bacterial characteristics (i.e.: circular genome, the bacterial
genome replicates in the same way as binary fission, the inner wall is bacterial in nature)
-mitochondria come from binary fission from the egg of the mother
-the same story can be applied to chloroplasts
Slide 7:
Endosymbiosis of Eukaryote Cells
-2 events that get us photosynthetic prokaryotes (i.e.: the chloroplasts)
-in the algae (single-celled photosynthetic protozoans) there is another symbiosis step
-eukaryote cells incorporate small photosynthetic eukaryote cells
-4 membranes around the plastid in the algae
Slide 8:
-creates diverse eukaryote group
-chlorophyte green algae lead to plants
-2 organisms lead to multicellular stages
Slide 9:
-at this time, the algae is the primary producer in the ocean
-marine environment stage is set and single-celled producers allow for this
Slide 10:
-many stationary protists
Types of Protist Locomotion
1) Amoeboid (uses fluid cell and constantly changing shape)
2) Flagellar
3) Ciliary
-animal-like protists (protozoans) are the most motile
-flagella found paired in plants and single in animal protists
-cilia represent many short flagella
Slide 11:
Amoeboid Movement
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