|MadSci Network: Evolution|
Jonathan: Sorry for the delay, this question disappeared in my inbox. You pose an interesting question, which has a couple of answers/thoughts. First, you are also asking in a way, that if we rewound the tape, would we get the same result in the end, and the answer to that is probably not. There would most certainly be bacteria and complex organisms, something akin to mammals perhaps, but humans for humans sake might not exist. Evolution doesn't necessarily strive to make the most energy efficient shapes, there is nothing as awkward as a sloth, or a hippo out of water. Most of the changes that occur with evolution are stochastic in nature and there is as much pressure to keep advantageous traits as to not discard ones that cause no harm. The existence of creatures in the past, on a geologic time scale, like dinosaurs, is again, not a consideration of energy efficiency per se, but overall efficiency of the organism to survive and reproduce. If we look at the components of cells that actually make energy, the mitochondria in eukaryotes, and more specifically the F1/F0 ATPase, which actually makes ATP from the proton gradient in eubacteria and prokaryotes we can measure how 'efficient' this machine is, (It is actually a motor) and it is one of the most efficient rotors on Earth. Bacterial motility by flagella is also an extremely efficient process. If you think about how little food you actually need in a day to survive, it is actually amazing how well we process carbon sources into energy. As we can clarly witness from the amazing diversity of life on the planet, there is no 'correct' structure, and many organizational patterns work from single-celled to organisms as complex as frogs and humans. I encourage you to read the first few chapters of any biology text, or biochemistry text on phylogeny and evolution to appreciate the amazing ability of nature to try a nearly endless number of possibilities. Thanks -Matt-
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