General > Off Topic
Two arguments that give the creationists the upper hand.
Endy:
Excerpt from Wikipedia:
Contrasting with the symbiotic models, these models argue that cilia developed from pre-existing components of the eukaryotic cytoskeleton (which has tubulin, dynein, and nexin—also used for other functions) as an extension of the mitotic spindle apparatus. The connection can still be seen, first in the various early-branching single-celled eukaryotes that have a microtubule basal body, where microtubules on one end form a spindle-like cone around the nucleus, while microtubules on the other end point away from the cell and form the cilium. A further connection is that the centriole, involved in the formation of the mitotic spindle in many (but not all) eukaryotes, is homologous to the cilium, and in many cases is the basal body from which the cilium grows.
An apparent intermediate stage between spindle and cilium would be a non-swimming appendage made of microtubules with a selectable function like increasing surface area, helping the protozoan to remain suspended in water, increasing the chances of bumping into bacteria to eat, or serving as a stalk attaching the cell to a solid substrate.
Regarding the origin of the individual protein components, an interesting paper on the evolution of dyneins[1][2] shows that the more complex protein family of ciliary dynein has an apparent ancestor in a simpler cytoplasmic dynein (which itself has evolved from the AAA protein family that occurs widely in all archea, bacteria and eukaryotes). Long-standing suspicions that tubulin was homologous to FtsZ (based on very weak sequence similarity and some behavioral similarities) were confirmed in 1998 by the independent resolution of the 3-dimensional structures of the two proteins.
Evolution of Flagella Wikipedia
Pretty conclusive, if a bit technical.
What's more interesting is that it's convergently evolved in bacteria, eukaryotes and, archaebacterium. Seems to be a better example of evolution in action to me.
shvarz:
Here is a spunky video explaining (in easy and visual form) a lot of the research on flagellum evolution:
Link to youtube, as the board does not allow video insertion
Testlund:
Ok, that's something worth pondering. Found some other interesting videos through that link.
Numsgil:
If you're looking for crazy youtube videos about bogus science, try finding one about the expanding earth theory. The idea is that plate tectonics is untrue, and rather than continents floating around, the earth is expanding and the ocean is where the expansion came from. At the beginning of the earth, the theory goes, the earth was much smaller and all the continents touched each other. Over time the earth grew in size and the continents ripped apart.
EricL:
--- Quote from: Numsgil ---If you're looking for crazy youtube videos about bogus science, try finding one about the expanding earth theory. The idea is that plate tectonics is untrue, and rather than continents floating around, the earth is expanding and the ocean is where the expansion came from. At the beginning of the earth, the theory goes, the earth was much smaller and all the continents touched each other. Over time the earth grew in size and the continents ripped apart.
--- End quote ---
You mean that's not really the case? Stupid US public schools. Next you'll be telling me the earth actaully goes around the sun or something else equally as silly...
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