Well, where do comets come from then??? Why do we still have comets around if they only last 100,000 years or less? When did they form? Just 100,000 years ago and if so, how? Will there be anymore comets when these ones burn up? Or do Oort Clouds really exist?
Comets are leftovers from the formation of the solar system.
And yes, the Oort Cloud exists. It's been directly observed. Same with the Kuiper Belt. We've detected quite a few objects out there.
Not all comets get burned up by the Sun - most of them are still sitting out in the Oort Cloud, too far from direct sunlight for anything to happen. But there are a lot of objects out there - as they move around in their individual orbits, occasionally they interact with each other gravitationally. This sometimes results in a comet's orbit getting changed, which sometimes brings it closer to the Sun, and we get a nice view.
There's no magic limit of 100,000 years on a comet's life. Their existence depends on their initial size and how much direct sunlight they get, and what they run into (remember Shoemaker-Levy, when it got caught by Jupiter's gravitational pull?).
Where in the world are you getting your info, Flyer? Did you read some report about an individual comet that's only expected to last another 100,000 years and think that meant all comets had some sort of shelf life?
My question is: Does this mean the authors are saying that natural selection was not the cause of the evolution of the eukaryotic cell from the prokaryotic cell?
No. They're saying that complex life was dependent on the formation of mitochondria, and that this was apparently an event of unique importance. It's possible that similar adaptations from prokaryotes may have happened at other times, but that the existing eukaryotes thought they were tasty and/or out-competed them. Or that we just aren't aware of them - we aren't omniscient after all.
Nothing whatsoever in the material you quoted contradicts the theory of evolution. At all.
[qs]And if true what effect does that have for The Darwinian and neo-Darwinian theory of gradual descent by random mutution and natural selection? /qs
None. Random mutations of unique significance happen all throughout history. All vertebrates are related to a common ancestor, just as all eukaryotes are related to a single common ancestor. The development of the backbone was no less a singular and massively important development in the history of modern biodiversity than the development of mitochondria - without either adaptation, life on Earth would look MUCH different than it does today.
You could take basically any example of an extremely successful adaptation and say similar things.
But one-time mutations that make massive effects on the appearance of biodiversity a few million years later do not contradict the theory of evolution - rather, they support it.
The development of mitochondria allowed for the development of more complex organisms which were able to take over a rather large unoccupied niche and thrived. That's all, and that's exactly what we'd expect given mutation and natural selection.
Evolution doesn't require that similar adaptations, if successful, must happen repeatedly and independently. It does happen sometimes (see the eye), but evolution is not guided by anything more than survival and reproduction.
The Platypus is a monotreme, which are hypothesized to have branched into marsupials (meaning the platypus and, say, a kangaroo would share a common ancestor).
There aren't many extant species of monotremes around, and the platypus just looks damned weird, so there are a lot of old wives tales and false perceptions around. But the platypus fits into the tree of life just like any other species.
Fossil evidence told us a little, but genetics has revealed an awful lot more about the ancestry of the platypus. You should check out the wiki page at the very least.