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Lecture 13

BIO SCI 94 Lecture 13: Protist Part 2Premium


Department
Biological Sciences
Course Code
BIO SCI 94
Professor
Brad Hughes
Lecture
13

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2/4/19
How Do Protists Obtain Food?
Bacteria and Archaea have many ways to get food
Evolution of novel methods for finding food important in diversification of protists
Protists ingest food-eat bacteria, archaea, and other protists whole
Feeding methods:
Ingest packets of food
Absorb organic molecules from environment
Perform photosynthesis
Some uses combination of feeding methods
Some lineages can use all three methods
Ingesting Feeding
Ingestive lifestyle-eating live or dead organisms, scavenging organic debris
Some protist big enough to ingest bacteria and archaea whole
Phagocytosis-prerequisite for endosymbiosis→ chloroplasts
Many hunt prey
Some attach themselves to surface
Absorptive Feeding
Absorptive feeding- nutrients cross plasma membrane from environment
Common among protists
Decomposers-feed on detritus, dead organic matter
Live inside other organisms
Parasite-absorptive species damage host
Photosynthesis-Endosymbiosis and the Origin of Chloroplasts
Eukaryotes didn’t have necessary parts for photosynthesis
“Stole” parts using endosymbiosis
Endosymbiosis theory
Protist engulfed cyanobacterium→ birth of eukaryotic chloroplasts
Evidence for endosymbiotic origin for chloroplast:
Chloroplasts similar to bacteria
Animals cells/protists have endosymbiotic cyanobacteria
Chloroplasts have circular DNA molecule with genes similar to
cyanobacterial genes
A protist group has chloroplast with layer of peptidoglycan
Molecule found in cyanobacteria cell walls
Photosynthesis-Primary vs Secondary Endosymbiosis
Hypothesis:Endosymbiosis leading to photosynthesis occurs first in common
ancestor of plantae
Ancestor birthed all plantae subgroups
Chloroplasts in four major protists lineages
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