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| Evolution | |
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| Topic Started: 26 Oct 2009, 01:13 PM (805 Views) | |
| ARAZEC | 5 Nov 2009, 07:12 PM Post #91 |
This Person Has No Life
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no its not the origin of life i am asking you about i want to know from now going backwards in time ending at the blob.....in a ruff time scale so i can see like when the blob evolved ears and stuff |
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OTTOR never BE SORRY | |
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| conradw | 5 Nov 2009, 07:15 PM Post #92 |
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Mud Vile
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the blob won't evolve ears until looooong after it stops looking like a blob. It would be looking more like a rodent i think. Abiogenesis: life from not-life Edited by conradw, 5 Nov 2009, 07:16 PM.
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| conradw | 5 Nov 2009, 07:39 PM Post #93 |
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Mud Vile
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maybe this will help. I got it from the wikipedia article for the timeline of evolution (it isn't my own work) The basic timeline is a 4.5 billion year old Earth, with (very approximate) dates: 3.8 billion years of simple cells (prokaryotes), 3 billion years of photosynthesis, 2 billion years of complex cells (eukaryotes), 1 billion years of multicellular life, 600 million years of simple animals, 570 million years of arthropods (ancestors of insects, arachnids and crustaceans), 550 million years of complex animals, 500 million years of fish and proto-amphibians, 475 million years of land plants, 400 million years of insects and seeds, 360 million years of amphibians, 300 million years of reptiles, 200 million years of mammals, 150 million years of birds, 130 million years of flowers, 65 million years since the non-avian dinosaurs died out, 2.5 million years since the appearance of the genus Homo, 200,000 years since humans started looking like they do today, 25,000 years since Neanderthals died out. |
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| Junior | 5 Nov 2009, 07:44 PM Post #94 |
Ub3r Shrum
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did neanderthals coexist with humans? or were humans not around back then, or were they not called humans? |
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Here I am, On the road again. There I am, up on stage. Here I go, playing the star again. There I go, turn the page. | |
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| Concolor | 5 Nov 2009, 08:05 PM Post #95 |
Death
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@ARAZEC: While the others discuss abiogeneses, let's stick to evolution for a while. There's a great book about that called The Ancestors Tale, but I don't remember it so here's the highlights of our history as far as I remember bits and pieces of what I've learned from various sources, oh and backed up with numbers from the interwebs of course: Of course highlights are misleading, as life is a continuum, but anyway. If we trace our ancestors back about 30 000 years we get to the folks that were some of the earliest to show advanced use of tools and intelligence and so many scholars call them (and thereby us) homo sapiens sapiens as in "really clever man". Before that, somewhat arbitrarily, the lineage is called homo sapiens (clever man). If I remember correctly, at that time there was also a few homo sapiens neanderthalensis around (neanderthals) and that the people who would later become our ancestors shared enough genetic material with those guys to have a certain degree of interbreeding (i.e. there were two races). Other species of homo, such as homo floresiensis has been around until 10 000 years ago. Ok this is taking too long. Homo sapiens is the name we use for the lineage that goes back to about 1.5-2 million years ago when it was called homo erectus (upright man). Before that was homo habilis etc. Before this the name Australopithecus because the biologists that named these guys felt they were old enough not to be called homo. About 6-8 million years ago we enter the period where the lineage that will later lead to us separates from the lineages that will later lead to many of the other great apes, such as gorillas and chimpanzees. Before that was of course the time when lineages that would later lead to other modern apes and monkeys split apart from "our" line (lemurs and stuff). Remember that at this time, there were no humans, apes, monkeys, lemurs, dogs, cats whatever. There were a bunch of other animals whose offspring would later through a large number of generations would lead to the animals we have today. Anyway, mammals have ancestors that survived the extinction of the dinosaurs 65 million years ago. Before this these guys co-existed with the dinosaurs, and also share a common ancestor with them several hundred million years ago. Their common ancestors are the ones that took the step from sea-dwelling to land-walking. This was not fish, as fish is the name we have for modern animals that come from lineages after some of the species that stayed behind in the waters back then (almost 500 million years ago). These guys again came from worm like creatures which again came from simpler multi-cellular life forms. This was around the time that sex became a part of reproduction. Multi-cellular life forms came from single celled life forms (in "our" case eukaryots, which was formed by the combination of two prokaryots hundreds or even thousands of billions of years ago). That's my understanding of it. |
 
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| Concolor | 5 Nov 2009, 08:08 PM Post #96 |
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Death
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OK, thanx conradw. Your numbers are probably more correct than mine 
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| Luemas | 5 Nov 2009, 09:49 PM Post #97 |
All ur Walrus R belong to Me
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Ok, wait, so eukaryotes came from 2 prokaryotes? I'm missing this here. Because we're studying this in Biology, and if 2 Prokaryotes merge it isn't going to make Eukaryotes, or a nucleus, or membrane bound organelles, etc. |
YOU MADE ME   | |
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| conradw | 6 Nov 2009, 04:35 AM Post #98 |
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Mud Vile
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Luemas: what you're talking about now is a theory called Endosymbiosis. This postulates that the organelles found in eukaryotic were at one time symbiotic prokaryotes (in fact, because they have their own genetic material and reproduce semi-independently of the cell, you might suggest that they still are, except for the fact that they can no longer survive outside the cell). This is a theory I found fascinating, and I think its well worth a read. @Junior: Yes, Neanderthals and modern humans did coexist. Although at the time that they did, they probably didn't look too dissimilar. You'd be forgiven for thinking they were both 'humans' |
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| Concolor | 6 Nov 2009, 05:13 AM Post #99 |
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Death
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@conradw: I also see no reason for not calling Neanderthals humans. @Luemas: modern eukaryots and modern prokaryotes are of course dissimilar in lots of more ways than just eukaryots having more than one set of DNA. But remember that each strand has had billions of years to change and develop since they first parted. That is why they have different organelles etc. |
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| ARAZEC | 6 Nov 2009, 05:35 AM Post #100 |
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This Person Has No Life
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i do appreciate all the information but its really far fetched sounding.......  why did the first cell split? |
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OTTOR never BE SORRY | |
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| Concolor | 6 Nov 2009, 06:21 AM Post #101 |
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Death
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@ARAZEC: Ah, that's the beauty of science. The discoveries we make through the scientific method can be so astounding that they seem outright impossible at first glance. Just think about the relativity of time, how it moves slower at the foot of the empire state building than at the top. That doesn't make sense at all! But common sense isn't adjusted to account for relativity of time and space, it's not tuned for the vastness of space or the minute details of the atoms. It's not used to contemplate the enormous time-scales upon which our ancestors have developed and continents have drifted and planets, solar-systems and galaxies are formed. To us it's just all very strange and unfamiliar, but also breathtakingly amazing. Why did that first cell split? I don't even know if you could call the first replicators cells even. Why do radioactive atoms decay? (I'm just asking that rhetorical question to show how little I know of what causes these events to happen) Oh, and one thing I'm wondering. When you think of the early forms of life, do you think of cells the way you can see them in microscopes today? Because that is one thing one can be pretty sure about is that they most probably did not look like that. Our modern cells have billions of years of development behind them making them as complex as they are today. Early life would most probably have been a lot simpler (depending on how far back you go), and I guess maybe that's what you mean by "blob". A primitive membrane with some DNA or RNA inside it perhaps? (Now I'm just thinking loudly) |
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| conradw | 6 Nov 2009, 06:56 AM Post #102 |
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Mud Vile
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If you take the time to watch that youtube video I linked to, you might have a lot of the answers already. The first cells would certainly not look like the ones we have today. they would probably have been RNA based, as RNA can both act as a coding store as well as an enzyme. The first cells would probably have divided for purely mechanical reasons: as the cell got more and more full and the membrane got larger and larger, it would get more and more likely to sheer with the two sections then resealing. |
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| Concolor | 6 Nov 2009, 07:09 AM Post #103 |
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Death
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Now we're closing in on the field of abiogenesis here. Though I think the hypothesis presented in the video is an interesting, I would point out that there are loads of other hypothesis on how the process we call 'life' began on earth and that the entire field is yet rather new and unexplored. So be prepared for amazing discoveries Exactly how this process begun is of course not relevant for the evolution-process itself. Just like it does not matter if your zink-bucket is made by welding together different pieces of metal, or carved or extruded from a single block, it holds water nonetheless 
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| conradw | 6 Nov 2009, 07:40 AM Post #104 |
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Mud Vile
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However, I would say that some of the mechanisms evolution are pertinent in understanding how life began. living cells were not spontaneously generated, and it may be useful to phrase it in evolutionary terms. But yes, you're right. after all, the book was called On the Origin of Species, not the origin of Life. |
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| Concolor | 6 Nov 2009, 07:59 AM Post #105 |
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Death
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That is an excellent point, conradw. And as i stated in my post #9 in this thread, I do not believe you require anything living at all to have an evolutionary process as long as the right prerequisites are present. (Then again you may define 'life' in such a way that they will always coincide with this process) |
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