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15 Cards in this Set
- Front
- Back
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To review…
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Possible to test for vicariance
Keep in mind: what may act as a barrier for one kind of organism may aid dispersal for another kind of organism (e.g., Isthmus of Panama (3 MYA)—barrier to marine species, avenue of dispersal for terrestrial and freshwater species) Oceanic island fauna and flora originate mainly by dispersal—can be followed by speciation on the island |
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Difference between vicariance and dispersal
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In vicariance, the barrier is formed.
In dispersal, the barrier already exists |
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You can think of the relationship between an area and its species as analogous to host-parasite evolution, where the area is like the “host.” (6)
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1) Cospeciation (like vicariance)
2) Host Switch (like dispersal) 3) Independent Speciation 4) Extinction 5) "Missing the Boat" 6) Failure to Speciate |
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Diversity in prokaryotic metabolisms (4)
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Photoautotrophs = photosynthetic organisms that harness light energy to drive the synthesis of organic compounds from carbon dioxide
cyanobacteria, as well as all photosynthetic eukaryotes Chemoautotrophs = Need only CO2 as carbon source, but use chemical energy from oxidation of inorganic substances (eg. hydrogen sulfide, ammonia, ferrous ions, others) Photoheterotrophs = Can use light to generate ATP but must obtain their carbon in organic form. This mode of nutrition is restricted to certain prokaryotes. Chemoheterotrophs = Must consume organic molecules for both energy and carbon. |
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How did we get eukaryotes?
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Endosymbiotic theory, popularized by Lynn Margulis in 1980’s
*Make sure you look at slide 11 |
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Evidence for endosymbiotic origin of membrane-bound organelles (7)
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Mitochondria and plastids similar in size to many prokaryotes
Mitochondria and plastids have a double membrane Mitochondrial and plastid DNA is a single circular molecule and of similar size to DNA of prokaryotes New mitochondria and plastids are formed only through a process like cellular fission Membranous structures of plastids similar to those of cyanobacteria Some proteins encoded in the nucleus are transported to the organelles. This is consistent with an increased dependence on the eukaryotic host after forming an endosymbiosis. Organelles' ribosomes are like those found in bacteria |
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Lateral/horizontal gene transfer among prokaryotes
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Transfer of DNA that is not from parent to offspring or daughter cell
-Transformation—uptake of “naked” DNA from the environment -Conjugation—DNA copied from a plasmid or chromosome is transferred to a recipient cell -Transduction—movement of DNA from one prokaryote to another via a bacteriophage Because new genetic material is so easily incorporated into a bacterium, a few biologists believe that there are no prokaryotic “species” |
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Symbiogenesis
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Proposed recently by Margulis and Sagan in Acquiring Genomes (2002)
Def.: long-term symbiosis that leads to evolutionary change -Use morphological species concept -Claimed to be a major force in speciation—this is radically different from what you’ve been taught in this course Note: M&S are not opposed to evolution as the source of biodiversity, but think it happens in a different (yet still natural) way |
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The “neo-darwinian” view
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Mutation --> new allele --> differential reproductive output among individuals in a population (because of competition for resources and mates) --> speciation
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Margulis’ view (3)
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Cooperation, not competition, is the driving force for speciation
Microbes are too often overlooked Acquisition of a genome (through symbiosis) could be considered a means of fairly rapid evolutionary change |
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Examples given for symbiogenesis: Example 1
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1) Photosynthetic animals
Elysia viridis: always green; derived from grey non-photosynthetic ancestors; harbor photosynthetic algae |
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Example 2
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2) Lichens:
Often mistaken for moss Symbiotic relationship between a fungus and an alga or cyanobacteria—organisms of similar size 25% of all fungi are obligate partners in a lichen Cells propagate together and can form stalk-like, leaf-like structures |
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Other examples
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Cows, termites: harbor microbes that break down cellulose of plant cell walls
-Such organisms wouldn’t survive without their symbionts Humans: also have microbes in our guts that synthesize B and K vitamins; oral spirochetes; underarm bacteria -Sickness as a change in the ecological relationships within members of the symbiosis |
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More examples
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Corals: zooxanthellae
Plants: nitrogen-fixing bacteria Plants: Ardisia crispa - have bacteria in their ruffled edges, if they are not there, the plant will not flower The flashlight fish (Photoblepharon steinitzi) of the western Indian Ocean harbors bioluminescent bacteria in a structure ventral to the eye. |
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Introduced species (Introduced to new environments)
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Human-mediated dispersal
Cane toad Oysters Fire ants Brown tree snake Snakehead Kudzu *LOOK AT SLIDES 26-32 - observe endemic things etc. |
