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Origin of Eukaryotes
- -some question the endosymbiotic origin (aka fusion hypothesis) as the main driver behind it
- -evidence from the PVC superphylum (superphyla of bacteria), which shares many features w/ Eukarya (and not necessarily w/ Archaea)
- -therefore this superphyla may have served as
- ancestrial "stock"
- -& the evolution of the many major features of
- Eukarya may have been present in some Bacteria
- & evolved in steps
-
Essential role of Prokaryotes
- 1. Decomposers
- 2. Symbiotic relationships (mutualistic)
- ex: 500-1000 species in our intestines that help w/
- digestion
-
Prokaryotes Impact On Humans (Bad)
- 1. 1/2 of all human parasites are bacteria (deadliness caused by toxins)
- 2. Can be used as bioterrorism agents (ex: anthrax)
- 3. Difficult to defeat given rapid evolution
-
Prokaryotes Impact on Humans (Good)
- 1. Fermentation for food
- 2. Research
- 3. Genetic modification & bioengineering
- 4. Bioremediation-remove pollutants from the environment (ex: oil spill in Gilf of Mexico)
- 5. Decomposers
- 6. Mutualistic symbiosis
- 7. Provide scenic landscapes
- 8. Oxygenation of the Earth
-
Protists (Eukarya 2.1 bya origin)
General Characteristics
- -mainly unicellular
- -mainly aquatic
- -some asexual, some sexual, some both
- -they are all Eukaryotes
-
Protists-Origins: Why so diverse?
Endosymbiosis (process of engulfing cells that become endosymbionts & ultimately organelles/plastids)
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Primary Endosymbiosis
One heterotrophic Eukaryote engulfs a photosynthetic cyanobacterium
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Secondary Endosymbiosis
Red or green algae being engulfed by another Eukaryote
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Diplomonadida (Giardia) & Parabasalas (Trichomonas)
- -Lack plastids
- -Mitochondria lack DNA
-
Euglenozoans
Spiral or crystalline rod at base of flagella
- A) Kinetoplastids (Trypanosoma)
- B) Euglenids (Eugela)
- -Photosynthesis or be heterotrophs
-
Alveolates & Stramenopilans
Red algae symbiont
-
Alveolata
Membrane bound sacs just under plasma membrane (unknown function)
ex: Dinoflagellates, Apicomplexans (Plasmodium-malaria), Cilliates (Paramecium)
-
Stramenopilans
- Hairy flagellum and smooth flagellum
- ex: Oomycetes, Golden Algae, Diatoms, Brown Algae
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Stramenopilans
1. Brown Algae & "Seaweed"
- -seaweed = some type of algae that have specialized tissues & "organs" like those seen in plants, but they have evolved independently
- ex: Alternation of generations
- Multicellularity & Tissue formation
- Larger in size w/ parts (holdfast, stipe, blades)
-
Cercozoans & Radiolarians
Move by threadlike psuedopodia
- A) Cercozoans (Forams-CaCO3 shells)
- B) Radiolarians (SiO2 shells)
-
Amoebozoans
- -amoebas w/ lobe shaped psuedopodia
- -these are thought to be the closest relative to the Fungi & Anamalia
ex: Gymnoamoebans, enamoebans & slime molds
-
Rhodophyta (Red Algae)
Chlorophyta
Charophyta
- -Chlorophyll a
- -endosymbiotic event w/ a cyanobacterium--->led to chloroplasts
-
Rhodophyta (Red Algae)
- -phycobillins
- -some "seaweeds"
-
Green Algae (Chlorophyta & Charophyta)
- -Carotenoids
- -Chlorophyll b
- i. chlorophyta
- ii. charophyta (stoneworts)
- -sister group to plants
-
Synapomorphies Charophyta share w/ Plants
- 1. Similar percentage of cellulose in their cell walls
- 2. Peroxisome enzymes that minimize loss of organic
- products
- 3. Similar structure to their flagellated sperm
- 4. Similar chloroplast DNA
- 5. Formation of phragmoplast (scaffold for formation
- of the cell plate at the end of a miotic division
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