Originally posted by jaywill
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For the record there is very little difference between "Macroevolution and Microevolution" its a concept developed by people who dispute the theories surrounding evolution.
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So what if that is true? Is the discrimination not useful because of that fact alone?
The micro / macro ...[text shortened]... cro evolution is a useful and valid aspect of the whole evolution discussion IMO.[/b]
Ok granted I can see why the Macro/Micro can be a useful term. However I think your major problem here is not being able to visualize how long a Billion years is. I'm very glad that you accept the old earth by the way, there is no way and very little point in discussing evolution with someone who doesn't.
Taking the example of the fruit fly: If we can see speciation(You know what defines a species?) and noticeable changes in morphology, within a fly over the period of a few generations(a few days in this case) then apply this to a billion years and a natural environment and I can easily see there being many many creatures who look nothing like the original fruit fly but have certain features which mark it as having the fruit fly somewhere in it's ancestry, six legs, compound eyes etc etc.......
Apply the same logic to bacteria and it goes further, I can easily visualize over a million(less actually) years how a bacterium could combine with neighboring bacteria, changing from unicellular to multi cellular. Thus changing not only species but actually being something completely different.
Same logic with the plant.
You seem to think that in larger creatures this would take only 1 or 2 generations. Taking the average mammal lifespan to be 20 years..... several million/20 gives a lot of generations even 1 million years is 50,0000 generations. And the effect is exponential, once 2 creatures become speciated, they themselves will start diverging in respect to environment, resulting in 4/6/8/10 species, and so on and so forth.
Specifically to your whale comment, all you need is a large aquatic mammal, which slowly adapts to the sea over say 5000 generations (gross underestimate). Look at humans in the space of a few generations on average we've gotten significantly taller on average. And a clear example of this is the size and shape of doors in older buildings (celts, Norman, viking kind of older). And I firmly believe if 2 groups of humans we're seperated for 1 million years, they'd look very very different and probably not be able to breed.
to kill 2 birds with one stone
Relationships of descent can be demonstrated in both ammonite and trilobite populations within the fossil record. As well as brachiopods, bivalves, echnoids etc etc. All of which can be shown to start out as 1 or 2 species further down in stratigraphy (older), then as one investigates further and further up stratigraphy they become vast and hugely divergent species..... Both trilobites and ammonites went from something as small as your hand to creatures as big as a table. And in the case of ammonites even larger (Car Bus).
Actually heres one for you; echnoids, think sea urchins, star fish, sea lilies etc. A clear spectrum of change can be show from the initial morphology of a small basic (round) sea urchin all the way through to the massive starfish, which have limbs that the sea urchin never had, we see today, and we still have highly adapted and evolved species of the original sea urchins also. Same with sea lilies.
These by the way are complete creature fossils, no bone matching required.
I'm going to ignore the comment about man looking down at lesser lifeforms. For several reasons; your assuming mans self awareness makes him superior to all other life. I judge success on span of existence, we haven't been here that long and we won't be if we carry on the way we are.
There was nothing quite like the trilobite, it was a successful predator, a successful herbivore... Effectively the trilobite filled every mode of life imaginable. It was also here longer, and survived more readily..... It was by every definition, except self awareness, far far more successful than us. As we're the dinosaurs actually.
Why would a designer allow a perfectly adapted creature such as the trilobite become extinct?
And relationship of descent fits the data better.....
There is much pre-cambrian life, look up stromatalites and the ediacara fauna....... The life explosion is more than likely the shift from soft bodied creatures being dominant to hard bodied creatures being dominant... An artifact of preservation nothing more.
Single celled life is incredibly complex because its been evolving the longest, I thought that would be clear. None of it can't be linked to other single celled lifeforms, we just don't have the ancestors anymore.
Divergent evolution is the adaption of 2 species with 1 common ancestor into 2 completely separate modes of life.... Creatures that share ancestry and look the same but have completely different adaptions for feeding, breeding, etc etc
convergent evolution 2 creatures, completely separate from one another with completely different ancestry, that have developed similar adoptions in morphology to facilitate a similar mode of life.....