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Think it through. If the legs get shorter and shorter, when are they too short to run properly?
When do the fins start growing?
How does a swimming Zebra with very short legs catch anything in the water?
I honestly have no idea.
However, speciation requires reproductive isolation, and that may be geographical rather than biological.
Thus, we conclude that such massive karyotypic changes have not resulted in full reproductive isolation, in stark contrast with theories assuming that chromosomal impairment during meiosis is responsible for complete sterility in hybrids (18), but in agreement with the description of fertile offspring across equine species (32, 33).The claim is that there were multiple chromosome-loss events.
See Speciation with gene flow in equids despite extensive chromosomal plasticity
I don't see just one trait but say ten or more traits, that would be required. This is a very large set of physical transitions for a species to undergo.Why do you think that fins are required before an animal is able to survive well in the water? You do know there are intermediate stages, right? And they don't require long legs OR fins.
And why do you apparently think that only one trait can change at a time?
The three currently recognised species of zebra (Mountain zebra, Plains zebra, Grévy's zebra) have different habitat preferences.
I don't see just one trait but say ten or more traits, that would be required. This is a very large set of physical transitions for a species to undergo.
I don't see how a Zebra with short legs could avoid getting bogged in the mud.
Where are the crocodiles? Hippopotamus are immune to crocodiles but Zebra are not.
Intermediate stages of what?
And thus they are reproductively isolated
Where are the predators?Intermediate stages from how they started to how the end up being well adapted to life in the water.
Yes. One hypothesises that the original species event involved a similar isolation.
Where are the predators?
Your transition is without the predators.
Given that they are found in different areas, it seems likely that an ancestral zebra species spread out, and adapted to different environments.
You seem to be trying to suggest that there's no good cause to think that's what happened.
Given that they are found in different areas, it seems likely that an ancestral zebra species spread out, and adapted to different environments.
You seem to be trying to suggest that there's no good cause to think that's what happened.
I don't see just one trait but say ten or more traits, that would be required. This is a very large set of physical transitions for a species to undergo.
I don't see how a Zebra with short legs could avoid getting bogged in the mud.
Where are the crocodiles? Hippopotamus are immune to crocodiles but Zebra are not.
Intermediate stages of what?
Because it's possible that there was a speciation event producing 2 or more species, and that the adaptation to the existing habitats happened after that.
You just pulled the ripcord.You seem to think that adding predators means that such evolution is impossible.
In my example I've tried to keep things simple because I'm describing the basic process, and I'm not intending to describe in detail how some real or hypothetical instance of evolution could take place. I'm trying to give an overview of the process itself. As such, I've kept it simple. In real life, there would be many genes controlling many traits, all of which are varying across the population, and there are many pressures acting on whether some individual survives or not.
The fact that I've kept things simple because the real life version is very complicated does not negate the plausibility nor the evidence supporting evolution by means of natural selection.
Not necessarily if they are related traits, as they evolve together. All of the traits are subject to constant randomly distributed variation and the selective environment for each trait includes the other related traits, not just the environment external to the creature.I don't see just one trait but say ten or more traits, that would be required. This is a very large set of physical transitions for a species to undergo.
That's pretty much what I said, isn't it?
A single group moves to different areas, becomes reproductively isolated, adapts to different environments?
You just pulled the ripcord.
Yes Kylie, it is a simple example but that is the problem is it not. The example you cited just doesn't really float.
But your talking about millions of years of gradual variation. Any species transforming from a tetrapod to a infraorder Cetacea, is extremely vulnerable during that slow transition. Mainly because it cannot swim or run properly during that transition. Regardless of how many traits are developing.Not necessarily if they are related traits, as they evolve together. All of the traits are subject to constant randomly distributed variation and the selective environment for each trait includes the other related traits, not just the environment external to the creature.
Well, we have:
Hypothesis A (what you said): a single group becomes geographically spread (e.g. in mountains and plains), subgroups become reproductively isolated, and adapt to different environments, thus forming 2 or more species.
Hypothesis B (what I said): a single group separates into 2 species through some unknown mechanism (in the case of zebras, alterations to chromosome number may be involved with this), and after that the two groups gradually adapt to different environments.
An example of hypothesis B would be the distribution of wild horses and wild donkeys (burros) in the Americas. The species had diverged in the Old World before arriving in the Americas.
Distinguishing between hypothesis A and hypothesis B (speaking in general) usually requires extensive knowledge about the past.
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