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BIO153H5 (211)


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Fiona Rawle

PROTISTS January 24  Protists = paraphyletic  Diversity in size, morphology and ecology MORPHOLOGICAL INNOVATIONS EVOLVED IN PROTISTS  Earliest eukaryote = single celled org, nucleus, endomembrane system, mitochondria, cytoskeleton, no cell wall  Common ancestor of eukaryote lacked cell wall  Eukaryotic flagella = made of microtubules, dynein, undulating motion occur  Bacteria+archaea = made of protein flagellin, rotating motion  Nuclear Envelope o Hypothesis - derived from infoldings of plasma membrane; may have given rise to ER too 
 ○ Evidence - infoldings of plasma membrane occur in some bacteria today; nuclear envelope of ER is continuous ○ Nuclear envelope separated translation and transcription
 ○ RNA transcripts = inside nucleus; translation = outside 
○ Allowed for alternative splicing and other forms of RNA processing; Control gene expression
 ○ new way to manage and process genetic info  Mitochondrion
 ○ Organelles that generate ATP using pyruvate as e- donor and O as e- acceptor ○ 1981: Lynn Margulis - Endosymbiosis Theory  Proposed mitochondria originated when bacterial cell took up residence inside eukaryote  Eukaryotic cells started to use cytoskeletal elements to surround and engulf smaller prey  Instead of being digested/engulfed, bacteria lived inside host  Engulfed cell survived by absorbing C w. high potential E from its host and oxidized them  Host = anaerobic fermentation (cant use O as e- acceptor)  Mutual adv existed = host supplied bacteria with protection and C compounds; bacteria produced more ATP than host could make on its own 
○ Symbiosis: individuals of 2 diff species live in physical contact
○ Endosymbiosis: org of one species lives inside org of another species ○ Evidence for Endosymbiosis Theory  size of average bacteria and replicate by fission - duplication of mitochondria takes place independently of division of host cell  Have their own ribosomes and manufacture their own proteins - mitochondrial ribosomes resemble bacterial ribosomes, poisoned by antibiotics that inhibit bacterial but not eukaryotic ribosomes  Double membrane  Have their own genome which are organized as circular molecules genes code for enzymes needed 
to replicated and transcribe mitochondrial genome Structures for Support and Protection  Microfilaments, intermediate filaments, microtubules form extensive and dynamic internal skeleton  Diatoms = surrounded by glass-like silicon-oxide shell; Shell is made up of 2 pcs that fit together in a box and lid arrangement ○ Dinoflagellates = cell wall made of cellulose plates ○ Foraminifera = some lineages secrete intricate chambered test/shell of calcium carbonate; other lineages and some amoebae = cover themselves with tiny pebbles ○ Parabasalids = distinctive internal support rod, consisting of cross-linked microtubules that run the length of 
the cell ○ Euglenids = collection of protein strips located under plasma membrane; Strips supported by microtubules and stiffen cell ○ Alveolates = distinct sac like structure (alveoli) under plasma membrane that help stiffen cell Multicellularity ○ Multicellular = more than one cell ○ Cells have be specialized for diff functions ○ Not all cells express same genes ○ Synapomorphy shared by all brown algae and all plasmodial and cellular slime moulds, some red algae 
lineages ○ Bacteria that can aggregate and form frui
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