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Single-Celled Species' Genome As Complex As Ours?
An anonymous reader writes: "A new paper reports on the sequencing and analysis of the genome of a single-celled species known as Tetrahymena thermophila. This ciliate (like the Paramecium people look at in school) has some 27,000 genes, or nearly as many as humans. And despite existing as a single cell, this spcies encodes fantastic complexity and unusual features. For example, it has a primitive immune system that prevents the invasion of foreign DNA. Also, it is able to cordon off its germ cell lineage much as humans do with sperm and eggs. But Tetrahymena does this by having two nuclei within each cell, with one of the nuclei being held in reserve for sex. Basically, this species uses its genome complexity to function like a single celled chameleon, changing its shape and its properties in response to the changing environment. For example, when a new nutrient shows up in its neighborhood this species can build a kit to suck the nutrient in, degrade it, and turn it into cellular biomass quickly. Thus whereas humans use their genomic complexity in part to create a stable environment for the body, this species simply uses a genomic swiss army kit to make do with whatever environment it encounters."
Tetrahymena are non-pathogenic free-living ciliate protozoa. They are common in fresh-water. Tetrahymena species used as model organisms in biomedical researches are T. thermophila and T. pyriformis.
http://en.wikipedia.org/wiki/Tetrahymena
Wincopy
I feel it's worth pointing out that no where in the Origin of Species does Darwin discuss human/great ape/primate evolution. I'm not even certain he used the word "evolution", but don't quote me on that. Also, no true evolutionary biologist has ever said that humans descended from monkeys. It's that whole common ancestor thing. Lot's of branches, not straight line.
The human eye has a "design" error, in that the photosensitive layer is not in front, there are other cells above them.......
Actually, the mammalian (human) eye is optimized for the metabolic loads it requires. It turns out that there is no higher area of metabolism in your body than there is at the photoreceptor/retinal pigment epithelium interface. It is a highly oxidative environment and evolutionarily, you need the apposition of the photoreceptors up against a layer of cells that can deal with the shed outer segments and the metabolic loads induced by rod photoreceptors. The other advantage is that you can snuggle the photoreceptors up to these cells that have a direct connection (diffusion) to a vascular layer. If it were backwards, the blood vessels would get in the way of the image formation and cast shadows.
In mollusks, OTOH, the outer layer of cells is the photosensitive one. The eye is more sensitive to light, has no blind spot, and allows for more data processing in the retina itself. That may be one of the reasons why octopuses are so good at camouflage, their eyes are very sensitive.
Octopuses, squid, and cuttlefish have fairly sophisticated retinas that is true and you are correct about their anatomy. However, they do not process the same metabolic loads that the mammalian retina does and thus do not require the same degree of buffering, care and feeding that mammalian photoreceptors do. You have to be careful about using "sensitive" to describe eyes as that descriptive is dependent upon lots of things. Typically in most retinas it has to do with the ability of the opsin to capture a photon and the cell the opsin is in to transduce that signal.
All this is one more argument for evolution and against the "intelligent design" theory.
Intelligent design (ID) really does not even factor into either argument. ID is a religiously/politically motivated belief, not a theory that can be tested.
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