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The simple answer is that members of a species can produce fertile offspring. That's not a perfect definition, though.
They're a separate species, but still very close together. They can mate and produce offspring, but the offspring are sterile--a well-known intermediate step in speciation.Is a mule a separate species because from what I understand they are infertile (at least the male is, though apparently the female mule can occasionally, with difficulty, get pregnant)? From what I read a horse and donkey are separate species, but together produce mules, which are hybrids. So, if not a species, what do they count as?
That type of diagram specifically is not a good representation of evolution. Heck, a good portion of them even put humans as evolving from chimpanzees, which is incorrect.I didn't learn about evolution at school, so lots of things puzzle me. I do remember at primary school looking at a picture of humans developing from more ape like creatures and gradually becoming upright - and thinking...that is ridiculous! Made no sense to me, but then again I had no explanation as to why that would happen.
It is explainable, and actually rather simple. Even today, there are single celled organisms that reproduce both by "splitting into two cells" by themselves, and via sexual reproduction. Many are hermaphrodites entirely, but as can be seen in other species, the split begins with populations having ones that solely produce the "male" gametes (sex cells) mixed in with the hermaphrodites. The benefit of being male is that less energy has to be used up making sex cells, as these individuals only make one type. However, as you might note, the hermaphrodites still exist to keep reproduction going. An example of populations like that are certain stages of fern life cycles. Now, with sufficient males in the population, there can be a selective force on the remaining hermaphrodites to dedicate more of their cellular function to the female sex cells rather than making both. But, there is a give and take with that, hence why the mixed hermaphrodite and male populations still exist as well as male and female. With making male gametes, it makes it easier to spread genes without expending the energy of serving as the female, even as a hermaphrodite. However, energy is conserved far more with making only one type of sex cell. So, if conditions favor reducing energy consumption, there will be selective pressure for the remaining hermaphrodites to gradually dedicate more and more to making only the female sex cells. If conditions do not favor reducing energy consumption, then the selective pressure will be for them to remain hermaphrodites.But anyhow, one of my questions is, how on earth did different 'sexes' arise? If we all started from single-celled creatures and many creatures like amoeba and spyrogyra just split in two, so to speak, to multiply...well, how did creatures after that start getting male and female organs, not to mention wombs and female breasts or various forms of udders etc, to reproduce and feed their young? I mean, I can't see that there would suddenly be an animal (however 'primitive') suddenly develop a penis and close by, there is one that develops a vagina etc etc etc. So presumably, this would have to develop gradually, but I just don't understand how.
I don't know if you can explain the process in any way?
Hey, no, try at least to be polite.You know the 2LOT has zero to do with ToE, right? Right?!
Based on your ignorant comment/question, I'll assume you've never read or studied the laws of thermodynamics, let alone the second one. So here, save yourself some future embarrassment and take a moment to read this:
Second law of thermodynamics - Wikipedia
No, I had no expectations for the quality of the questions. Some people really don't know that much about biology or evolution, others know a bit, and their questions will reflect their knowledge accurately as long as they aren't asking them to be snide. I'd rather you not insult the questions or those asking them. Curiosity is a good thing, and I don't want people to be deterred from asking questions by making them face condescension.Sorry Sarah, I bet you were expecting better informed questions, and not the PRATT tripe creationists sites spew.
That's getting more into abiogenesis than evolution, which only works with existing life. However, existing biochemical pathways are often altered with genetic mutation. As to how the biochemical pathways originated, I can speculate, but the understanding of that is far lesser than the knowledge of how existing life changes over time in a population over generations.How did new biochemical pathways, which involve multiple enzymes working together in sequence, originate?
Every fossil is transitional, because evolution is a continuous process. Your generation is among many generations that transition from human to some future species. Due to the rarity of fossils, it is uncommon to see species to species transitions represented in them, but genus to genus and on higher orders of classification are very common.Charles Darwin admitted that the available fossil evidence didn’t support his theory of evolution. But he expected that plenty of evidence would be found in the coming years. Now, more than a century and a half later, the evidence still fails to support his theory. Where are the, expected, countless millions of transitional fossils?
Mules themselves are considered species hybrids, and are not functional as a species in their own right.Is a mule a separate species because from what I understand they are infertile (at least the male is, though apparently the female mule can occasionally, with difficulty, get pregnant)? From what I read a horse and donkey are separate species, but together produce mules, which are hybrids. So, if not a species, what do they count as?
Is a mule a separate species because from what I understand they are infertile (at least the male is, though apparently the female mule can occasionally, with difficulty, get pregnant)? From what I read a horse and donkey are separate species, but together produce mules, which are hybrids. So, if not a species, what do they count as?
Their fossils though tell us enough that we know they're different enough to be separate species for the purposes of classification.
There's the problem. You say "different enough to be separate species" like your use of the word "species" in that statement has meaning, but since your definition of "species" has nothing to do with "appearances" and everything to do with "fertile offspring": you're using a word with no inherent contextual meaning like it has meaning. What you're actually wanting to say is "we define a species by the way it looks" or "species is based on a system of morphology", true? Because clearly we don't know anything about the biology of fossils let alone the fertility of the offspring.
Species will have a degree of conformity in their physiology. It's enough to reliably distinguish most fossils from each other, but it can get difficult at times, and lead to arguments.There's the problem. You say "different enough to be separate species" like your use of the word "species" in that statement has meaning, but since your definition of "species" has nothing to do with "appearances" and everything to do with "fertile offspring": you're using a word with no inherent contextual meaning like it has meaning. What you're actually wanting to say is "we define a species by the way it looks" or "species is based on a system of morphology", true? Because clearly we don't know anything about the biology of fossils let alone the fertility of the offspring.
Morphological differences are used in the context of fossil species.
The fact that biology doesn't fit into neat little boxes that humans prefer is not a problem.
Species will have a degree of conformity in their physiology. It's enough to reliably distinguish most fossils from each other, but it can get difficult at times, and lead to arguments.
One of the interesting benefits of fossils being rare is that they normally depict species that are thousands of years apart or more, so the morphological differences even between "closely" related species in the fossil record can be easily seen through side-by-side comparison. So much so, that teeth or a part of a skull is usually enough to at least get to the genus level, if there are other fossils of that species already found. When you have very few pieces to start with, they can be kept in categorical limbo until enough are found to make a classification.Okay and how do we determine when morphology is a different "species"? Are the criteria of "morphology" a little more precisely defined? Or are we still at vague? In other words, how are we determining that a change from one species to another (in the past) is actually taking place?
Psychology.Talking about "species" with a vague definition of "species" is a problem. The first step in any form of meaningful communication is to properly define the terms so we know what we're actually saying. It doesn't appear that we can actually talk about "species" with any meaningful logical ability. Is there any other science that has this much problem defining the terms?
Okay and how do we determine when morphology is a different "species"?
In other words, how are we determining that a change from one species to another (in the past) is actually taking place?
Talking about "species" with a vague definition of "species" is a problem.
It doesn't appear that we can actually talk about "species" with any meaningful logical ability.
Okay I get that morphology can distinguish between a small many armed thing and a large biped. But how do we determine when a species has actually changed into another species?
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