BIOLOGICAL DIVERSITY CHAPTER 29 PROTISTS 10 31 first eukaryotic group membrane bound nucleus oldest prokaryote was 3500 million years ago oldest definite fossils of eukaryotes are 1 5 billion years old o similar to green algae o 2 billion years AFTER oldest prokaryote Protists very diverse group o catch all group if scientists cannot classify something they become a protist o truly funky phylogenetically multiple independent evolutionary lineages no characteristic unique to all protists primarily unicellular but some multicellular autotrophs o using light chemical forms for energy photosynthetic o carbon is obtained from carbon dioxide inorganic form of carbon heterotrophs mixotrophs o gain carbon and energy from external sources o differ from autotrophs in that the carbon source is organic animal plant fungi bacteria o use both autotrophic forms and heterotrophic forms in order to gain energy and carbon Protistan Evolution these evolutionary events make eukaryotic life possible o prokaryotic cells eukaryotic cells o asexual reproduction sexual reproduction binary fission sexual reproduction one cell splits into two daughter cells asexual more than one organism involved in reproduction o unicellular multicellular forms drive to multi tissue systems Theory of Endosymbiosis bound nucleus are characterized by internal compartmentalization other organelles like the mitochondria chloroplasts endoplasmic reticulum vacuoles move from prokaryotic cells to eukaryotic cells have a membrane organisms living together in a close association where both benefit o endosymbiosis o figure 29 2 o step wise 1 2 represents gaining a membrane bound nucleus infolding of the plasma membrane a there are existing prokaryotes that have the characteristic of an infolding membrane i increase surface area of the cell 1 2 increase food uptake food traps ii protect DNA better food particles get trapped in the folds 3 folds met and then the membrane fused around the DNA a something found in modern prokaryotes particularly when surrounding food particles 4 end result is gaining a modern eukaryotic cell with a membrane bound nucleus from the membrane and the endoplasmic reticulum from the folds a b first step toward an eukaryotic cell simple ancestral eukaryotic cell increased compartmentalization feeding understand this to understand endosymbiosis o many protists some prokaryotes feed by phagocytosis membrane surrounds the food source changes shape and engulfs the food then we have a membrane bound nucleus AND a food vacuole that contains the food item just taken in food vacuole is broken off of the cell membrane o enzymes flood into the food vacuole and break down the food item into its component pieces food vacuole itself breaks down or food particles go through vacuole membrane products of digestion move out into the cell ancestral eukaryotic cell to modern eukaryotic cell o ancestral eukaryotic cell encountered and consumed a bacterium if individual bacteria does not breakdown is NOT ingested then it can continue its life within the vacuole within the eukaryotic cell idea of endosymbiosis bacteria living within another cell symbiosis products taken up by bacterium using carbon and some of the energy from the eukaryotic cell through the bacteria s metabolic processes it releases energy and the eukaryotic cell gains the energy and uses it symbiotic eukaryote cell has extra energy gain from the bacteria the ancestral eukaryotic cell DOES NOT o symbiotic eukaryotic cell has an increased growth and reproductive rates selective advantage over time cells with the symbiote are selected FOR due to the extra energy and increased rates of growth and reproduction o the bacterium taken up by the ancestral eukaryotic cell is most likely a purple sulfur bacterium excellent energy producers bad energy harvesters over time the mitochondrion was formed powerhouse creating energy both were dependent on one another o just as phagocytosis was responsible for taking on the purple sulfur for mitochondrion phagocytosis took up photosynthetic bacteria became symbiotic and resulted in modern chloroplasts similar to cyanobacteria poor energy producers but excellent energy harvesters associated with sunlight autotrophic pathways were selected for evidence particular organelles are double membraned vacuole and around bacteria o both mitochondria and chloroplasts have double membranes o mitochondria and chloroplasts are capable of going through binary fission autonomously like bacterium do o mitochondria and chloroplasts have their own genomes very likely that purple sulfur and cyanobacteria are the mitochondria and chloroplasts of today Sheet who are the protists o kelp seaweed o malaria o phytoplankton drifting plants not plants diatoms green algae o sleeping sickness trypanosomes o amoebas o slime molds o paramecium roles of protists o major food source o cause disease fish small crustaceans humans etc at the base of most aquatic food webs some of the most deadliest diseases are caused by protists o major producers of oxygen 80 of Earth s oxygen come from protists Protists from Ecological Perspective mainly aquatic marine and freshwater o among the most abundant organisms in any aquatic food web o at the base of most aquatic food webs found in blood or body fluids liquid based environment aquatic autotrophic protists o phytoplankton drifting plants NOT plants floating protists and SOME prokaryotes ex cyanobacteria this is BACTERIA and phytoplankton photoautotrophs harvesting energy from light carbon dioxide water light into photosynthesis that creates oxygen food organic carbon o 80 of Earth s oxygen comes from phytoplankton includes some bacteria archaea cyanobacteria tend to respond well to pollution nitrogen or phosphorus phytoplankton blooms o lots of it coming along at once responding to a nutrient diatoms largest most abundant group of phytoplankton unicellular autotrophs attached or floating forms floating found drifting in water passive can be single or colonial stacks of individual organisms cells when they die they settle out to the bottom of the ocean or lake o used in science and diatomaceous earth paleontology reconstruction of what lakes were like 10 000 years ago temperature acidity sulfur levels etc based on diatoms diatomaceous earth dried up lake bed with thousands of years of dead diatoms that are mined and harvested then sold for various things toothpaste kitty litter pool chemical filters the shells themselves
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