Difficulty understanding evolution

[Adamchiv]

It's not mindfulness, it's a matter of the organism surviving long enough to reproduce before getting eaten or being killed in some other way.

But what's the governing factor in deciding when why or how a mutation will not pass down anymore? you said if the mutations are not useful anymore they just don't pass on. That really does emply mindfulness without an explination of how they don't pass on. If they don't have a mind (which we agree on) then how can they (or the gene pool) know they are not needed?

Its like a lottery ball dispenser, let's say to stop it you have to switch it off, its generating random balls, then it suddenly switches itself off because its done enough, its finally got the numbers right. That can't make sense unless there is a deeper understanding of why it suddenly switched off

 

[Ryan_m_b]

But what's the governing factor in deciding when why or how a mutation will not pass down anymore?

Natural selection* is the answer. If the mutation lowers an organism's fitness then it makes it less likely to reproduce, because the mutation affects fertility directly or it decreases survival chance meaning the organism will have fewer (or no) children. If a mutation leads to more offspring then in the next generation a higher proportion of the population will have that mutation.

*there are other causes like sexual selection but let's stick with the basics for now.

 

[rootone]

The governing factor is simply survival.
If a mutation makes no difference to survival or reproduction then it doesn't become more widespread in the gene pool over several generations.
If there IS a survival advantage it WILL eventually become widespread in the gene pool.
That is how evolution works, and after a long time of many accumulated changes you have in effect a new species.
Evolution is a gradual process, there are not sharp boundaries in time where some ancient species dies out to be replaced by an improved model.

 

[Adamchiv]

The governing factor is simply survival.
If a mutation makes no difference to survival or reproduction then it doesn't become more widespread in the gene pool over several generations.
If there IS a survival advantage it WILL eventually become widespread in the gene pool.
That is how evolution works, and after a long time of many accumulated changes you have in effect a new species.
Evolution is a gradual process, there are not sharp boundaries in time where some ancient species dies out to be replaced by an improved model.

Lets say though for example a big blue dot on a creature has emerged over years of survival of the fittest, its great for the creatures survival as it puts off its predator (this is hypothetical) so a perfect round blue dot has occurred eventually. This is probably quite standard I would say. So let's say that one of the offspring has a tiny mutation and that perfect blue dot now has a tiny little dot on the outline of it. It still deters predators and does not effect the survival rate, in fact, it reproduces more offspring. So why now does that useless little extra bit not remain in the future? it hasnt inhibited anything, and we see very perfect examples like the black widow spider, perfect red dot on its back, never ever going to turn into an oval, and were saying that its simply because the dot works?? I really find a problem with this

Im sorry the black widow was a really bad example, let's stick with my first example, I am sure there is an animal with a perfect dot in a certain place to use instead of the black widow (which I realized has a non descript shaped red part)

 

[BillTre]

Is there some sort of radial symatry in these colourations that makes these markings very easy to form rather than a complex process where millions of these animals die until its good enough

Here is a wikipedia entry on eyespots.
It talks about why they can be adaptive but also mentions some of the genes involved in their development.
Some of the genes involved make diffusable signalling molecules. They would diffuse out in a circular pattern from a small source (perhaps a few cells).
This would pattern the cells and explain circular shapes.

 

[Ryan_m_b]

Lets say though for example a big blue dot on a creature has emerged over years of survival of the fittest, its great for the creatures survival as it puts off its predator (this is hypothetical) so a perfect round blue dot has occurred eventually. This is probably quite standard I would say. So let's say that one of the offspring has a tiny mutation and that perfect blue dot now has a tiny little dot on the outline of it. It still deters predators and does not effect the survival rate, in fact, it reproduces more offspring. So why now does that useless little extra bit not remain in the future? it hasnt inhibited anything, and we see very perfect examples like the black widow spider, perfect red dot on its back, never ever going to turn into an oval, and were saying that its simply because the dot works?? I really find a problem with this

In that case the mutation would stay as it's neutral. Mutations can be advantageous, neutral or disadvantageous. The overwhelming majority of mutations in nature are neutral and stick around. A smaller number are slightly advantageous or slightly disadvantageous. These proliferate/are weeded out slowly over time. A rare few are strongly advantageous or disadvantageous.

 

[Drakkith]

By the way, I meant it requires a small isolated group for changes to pass down to a full group type of thing..

Not necessarily. If the offspring of one individual all carry over a beneficial trait that they can pass on to their offspring and so on and so on, the descendants of the original organism with that trait can, over time, out compete the others of their species and the trait can end up being in all of the individuals of the species. Isolated groups can and do tend to diverge from their original population rather quickly, as they are usually isolated in a different environment and don't have any mixing with the original genes that can remove or diminish various mutations.

So how come mutations on markings stop once it is succesful? Is it because those traits passed on in a big non isolated group become stronger?

Mutations don't stop. Variations in alleles (unique genes for a certain trait such as fur color, which arise from mutations) will tend to make the trait fluctuate slightly around some average value or particular pattern, but as you get away from this value the individual either becomes less fit or the change becomes less significant. Natural selection will tend to weed out those individuals that are less fit, and the other trait won't be selected for because it doesn't confer a tangible advantage.

So let's say that one of the offspring has a tiny mutation and that perfect blue dot now has a tiny little dot on the outline of it. It still deters predators and does not effect the survival rate, in fact, it reproduces more offspring. So why now does that useless little extra bit not remain in the future?

If, for any reason, that particular creature with the red outline survives to have offspring, then all of its genes will be passed on, even the ones that confer a neutral or negative trait (if it has any). So even if the red outline isn't contributing to its fitness at all, it can still be passed on through chance or because the creature was more fit due to other genes. This is exactly what we see in many, many cases. In your example, if the red outline is due to a change in genetics that can be passed on to its offspring, then the trait will remain in the population's gene pool until all of its descendants have either died without leaving offspring, or the trait is lost due to another mutation that then spreads.

 

[Adamchiv]

In that case the mutation would stay as it's neutral. Mutations can be advantageous, neutral or disadvantageous. The overwhelming majority of mutations in nature are neutral and stick around. A smaller number are slightly advantageous or slightly disadvantageous. These proliferate/are weeded out slowly over time. A rare few are strongly advantageous or disadvantageous.

Thats very helpful actually, that's led me a bit closer, I can work on that as a foundation and look into it

Not necessarily. If the offspring of one individual all carry over a beneficial trait that they can pass on to their offspring and so on and so on, the descendants of the original organism with that trait can, over time, out compete the others of their species and the trait can end up being in all of the individuals of the species. Isolated groups can and do tend to diverge from their original population rather quickly, as they are usually isolated in a different environment and don't have any mixing with the original genes that can remove or diminish various mutations.
Mutations don't stop. Variations in alleles (unique genes for a certain trait such as fur color, which arise from mutations) will tend to make the trait fluctuate slightly around some average value or particular pattern, but as you away from this value the individual either becomes less fit or the change becomes less significant. Natural selection will tend to weed out those individuals that are less fit, and the other won't be selected for because it doesn't confer a tangible advantage.
If, for any reason, that particular creature with the red outline survives to have offspring, then all of its genes will be passed on, even the ones that confer a neutral or negative trait (if it has any). So even if the red outline isn't contributing to its fitness at all, it can still be passed on through chance or because the creature was more fit due to other genes. This is exactly what we see in many, many cases. In your example, if the red outline is due to a change in genetics that can be passed on to its offspring, then the trait will remain in the population's gene pool until all of its descendants have either died without leaving offspring, or the trait is lost due to another mutation that then spreads.

Ahh so we have some some variencies among species, but they only pass on down that blood line and so then it doesn't effect the overall species and the trait is more likely to die out

 

[rootone]

Advantageous traits get passed down through generations of descendants precisely because they are advantageous (for survival).
Nature has no policy of deciding which members of a species are permitted to mate, so no pure 'bloodlines' exist.
They all merge as generation go by.
Traits which harm an individual's chance of reproducing tend to disappear in the overall population
Traits confering an advantage for reproducing will after several generations become the normal for that species.

There are some interesting variations on that theme though. a bee colony is one.
Here there is only a single reproducing queen bee, most of the colony members are infertile.
In my opinion though, the beehive is the creature, and the worker bees, drones etc are more analogous to
cells in animals.

 

[Adamchiv]

Advantageous traits get passed down through generations of descendants precisely because they are advantageous (for survival).
Nature has no policy of deciding which members of a species are permitted to mate, so no pure 'bloodlines' exist.
They all merge as generation go by.
Traits which harm an individual's chance of reproducing tend to disappear in the overall population
Traits confering an advantage for reproducing will after several generations become the normal for that species.

There are some interesting variations on that theme though. a bee colony is one.
Here there is only a single reproducing queen bee, most of the colony members are infertile.
In my opinion though, the beehive is the creature, and the worker bees, drones etc are more analogous to
cells in animals.

Thats a very interesting point, I remember richard dawkins describing worker ants as very similar to our bodily cells. Can I thank you rootone for your outstanding patience and information! You have been a real help with this

 

[phinds]

Can I thank you rootone for your outstanding patience and information! You have been a real help with this

Yeah, he tends to do that, but don't let's overdo the praise, it'll go to his head

 

[Adamchiv]

Yeah, he tends to do that, but don't let's overdo the praise, it'll go to his head

Lol You have all been very very helpful but how this person didnt lose their temper with me is very worthy of praise. I tend to find another problem within a solution, like god of the gaps but rather study of the gaps

 

[rootone]

I have a trait of not losing my temper, this has been an advantage so far.

 

[Jon Richfield]

Hi

I am and athiest and I believe on evolution, but there is an aspect of it that I can't get to grips with...

Thanks for any help with this

I really, REALLY do not mean to talk down to you, but your questions suggest that this is not the right forum for us to begin explaining at that level. It would take a looong time.

1: If you have too little idea of the nature of cell biology and reproduction, then first check out some school texts on biology or do some scouting around Wikipedia and even google.

2: If you do understand the role of nucleic acids in cell function and reproduction, and of cells in the construction of your body, then read some really sound basic introductions to evolution. I should recommend Daniel Dennett's "Darwin's Dangerous Idea" and maybe Dawkin's "The Selfish Gene" ((preferably 2nd or 3rd edition). They are not the only good books around, because semi-popular books on Darwinism have been a drug on the market for years now, but they are sound, make pleasant reading and are easily understood.

The reason I advise this is that as they stand, your questions are biological at a level similar to asking a physicist "Why doesn't the moon fall on my head, if as you say, it is attracted to me by gravitation." Yes, it is true that the attraction exists, but you see...

If you encounter any difficult points on the way, by all means come back and ask, but please keep the questions explicit.

 

[eltodesukane]

"why is it that our arms don't have big lumps all over them or, our ribcage have random points sticking out of each one, or an extra toe poking out the side of our foot."
-- Some do! I worked in a hospital and I saw myself many abnormal newborns, most of which dying at once or soon after. This is natural selection at work.
The healty ones live on, the dying ones die. No one said it was a happy process.
---
The regular use of Caesarean sections is having an impact on human evolution, say scientists.
More mothers now need surgery to deliver a baby due to their narrow pelvis size, according to a study.
Researchers estimate cases where the baby cannot fit down the birth canal have increased from 30 in 1,000 in the 1960s to 36 in 1,000 births today.
Historically, these genes would not have been passed from mother to child as both would have died in labour.
Researchers in Austria say the trend is likely to continue
"Without modern medical intervention such problems often were lethal and this is, from an evolutionary perspective, selection.
"Women with a very narrow pelvis would not have survived birth 100 years ago. They do now and pass on their genes encoding for a narrow pelvis to their daughters."
http://www.bbc.com/news/science-environment-38210837

 

[Adamchiv]

"why is it that our arms don't have big lumps all over them or, our ribcage have random points sticking out of each one, or an extra toe poking out the side of our foot."
-- Some do! I worked in a hospital and I saw myself many abnormal newborns, most of which dying at once or soon after. This is natural selection at work.
The healty ones live on, the dying ones die. No one said it was a happy process.
---
The regular use of Caesarean sections is having an impact on human evolution, say scientists.
More mothers now need surgery to deliver a baby due to their narrow pelvis size, according to a study.
Researchers estimate cases where the baby cannot fit down the birth canal have increased from 30 in 1,000 in the 1960s to 36 in 1,000 births today.
Historically, these genes would not have been passed from mother to child as both would have died in labour.
Researchers in Austria say the trend is likely to continue
"Without modern medical intervention such problems often were lethal and this is, from an evolutionary perspective, selection.
"Women with a very narrow pelvis would not have survived birth 100 years ago. They do now and pass on their genes encoding for a narrow pelvis to their daughters."
http://www.bbc.com/news/science-environment-38210837

Thats very interesting and once again another point that I forgot to think about, that is imperfection for sure

 

[haruspex]

there are other causes like sexual selection but let's stick with the basics for now.

But this is a significant part of the answer to the original question, which I take to be more along the lines of "why are there not more mutations of a fairly cosmetic nature?" I.e. how is natural selection so effective at weeding at even small imperfections?
Potential mates care about about genetic fitness. A lop-sided face can be a consequence of a childhood illness, so we have evolved to find such faces less attractive.

 

[Adamchiv]

But this is a significant part of the answer to the original question, which I take to be more along the lines of "why are there not more mutations of a fairly cosmetic nature?" I.e. how is natural selection so effective at weeding at even small imperfections?
Potential mates care about about genetic fitness. A lop-sided face can be a consequence of a childhood illness, so we have evolved to find such faces less attractive.

Yes that is very much to do with some of my problem I have understanding. That makes a lot of sense to me. Heres another issue, how do the male and female sexual organs develop side by side to work so well, same for the sperm and the egg. I kind of imagine it to go way back to bacteria or slightly after, but I really really don't understand how. Because they must develop and evolve separate from each other

 

[haruspex]

Yes that is very much to do with some of my problem I have understanding. That makes a lot of sense to me. Heres another issue, how do the male and female sexual organs develop side by side to work so well, same for the sperm and the egg. I kind of imagine it to go way back to bacteria or slightly after, but I really really don't understand how. Because they must develop and evolve separate from each other

It depends what you mean by working well together. Many aspects of this, in many species, are an arms race. The female side raises barriers so that only the fittest make it ( at the sperm level and higher), while the male side wages war with rivals, e.g. by leaving a plug in place or inflicting physical damage on the female.

 

[Bandersnatch]

Heres another issue, how do the male and female sexual organs develop side by side to work so well, same for the sperm and the egg. I kind of imagine it to go way back to bacteria or slightly after, but I really really don't understand how. Because they must develop and evolve separate from each other.

If you can find the time, read Matt Ridley's book: 'The Red Queen: Sex and the Evolution of Human Nature'.

 

[Adamchiv]

If you can find the time, read Matt Ridley's book: 'The Red Queen: Sex and the Evolution of Human Nature'.

Thats great I'll take a look at that, it really puzzles me but I know science will have the answer

 

[BillTre]

Heres another issue, how do the male and female sexual organs develop side by side to work so well, same for the sperm and the egg. I kind of imagine it to go way back to bacteria or slightly after, but I really really don't understand how. Because they must develop and evolve separate from each other

Yeast (a eukaryote and a fungi) and some bacteria have mating types, but they don't have sex organs. DNA exchange should only proceed between individuals with different mating types.
Although DNA is exchanged between these different mating types, they don't have sex organs or specialized reproductive cells like sperm, eggs, pollen, ovules (plant equivalent of eggs).

Sex organs are restricted to metazoan animals and plants have sex cells as a specialized sub-set of all the cells in their bodies.
Sex organs support the production of the gametes and are used for transferring gametes (sperm, pollen) so they can meet up with and fertilize eggs and ovules.

Some animals are both male and female (like most plants) at the same time. Some are first one sex than the other.
Again, selection has selected for them to work (either together or a lone) to achieve their function of reproduction (the most important biological property).

They don't always have to work together. Some worms will stab through the females skin with their "penis-like-thing" the get their sperm in the females body cavity where they will eventually find the eggs to fertilize. This requires little coordination with the females sex organs.
Some animals have sophisticated sperm storing organs that can keep sperm viable for months for fertilization long after copulation.

Just to add to the complexity, sex chromosomes can also evolve and change.

 

[Adamchiv]

Yeast (a eukaryote and a fungi) and some bacteria have mating types, but they don't have sex organs. DNA exchange should only proceed between individuals with different mating types.
Although DNA is exchanged between these different mating types, they don't have sex organs or specialized reproductive cells like sperm, eggs, pollen, ovules (plant equivalent of eggs).

Sex organs are restricted to metazoan animals and plants have sex cells as a specialized sub-set of all the cells in their bodies.
Sex organs support the production of the gametes and are used for transferring gametes (sperm, pollen) so they can meet up with and fertilize eggs and ovules.

Some animals are both male and female (like most plants) at the same time. Some are first one sex than the other.
Again, selection has selected for them to work (either together or a lone) to achieve their function of reproduction (the most important biological property).

They don't always have to work together. Some worms will stab through the females skin with their "penis-like-thing" the get their sperm in the females body cavity where they will eventually find the eggs to fertilize. This requires little coordination with the females sex organs.
Some animals have sophisticated sperm storing organs that can keep sperm viable for months for fertilization long after copulation.

Just to add to the complexity, sex chromosomes can also evolve and change.

Interesting, do you think that the human genitallia both male and female evolved independantly of each other for a long time? Was there a point when there was maybe one organism that reproduced and a split happened causing a male and female to evolve from it, one carrying the male components and the other the female components (in terms of reproductive cells) I don't mean suddenly there was man and woman like the biblical stories. I guess what I am trying to say is there must have been a point where male and female happened from when we evolved from bacteria up until we became two separate genders

 

[BillTre]

The two sexes had to evolve together in that they make haploid sex cells (sperm and eggs).
Haploid cells have only one copy of each chromosome. When the egg and sperm combine, they then have two copies of each chromosome (one from each parent), which makes them diploid, the normal state for animals. If they were haploid they would probably die before reproducing. If this were done without making the sex cells haploid, each generation would double its number of chromosomes, which would end badly.

Haploid cells are made by meiosis (special cell divisions that reduce the chromosomal number) rather than the more common mitosis (cell division without changing the chromosomal number). This requires males if there were females and visa versa. They have to had developed together.

 

[Drakkith]

Interesting, do you think that the human genitallia both male and female evolved independantly of each other for a long time? Was there a point when there was maybe one organism that reproduced and a split happened causing a male and female to evolve from it, one carrying the male components and the other the female components (in terms of reproductive cells) I don't mean suddenly there was man and woman like the biblical stories. I guess what I am trying to say is there must have been a point where male and female happened from when we evolved from bacteria up until we became two separate genders

This likely occurred very, very early on the history of life. Most likely when all life was still unicellular with perhaps some very simple multicellular organisms. By the time that the first fish species evolved, sexual reproduction had already been in place a long time.

 

[Vanadium 50]

By the time that the first fish species evolved, sexual reproduction had already been in place a long time.

True. A very long time. Around the time of the common ancestor of plants and animals, 1.2 billion years ago. Fish are only about 500 million years old.

 

[rootone]

Sexual reproduction must have initially been one of those lucky mutations.
Before that, and still now, there are many organisms which have their niche and are doing fine without it.
Once that exists though, evolution probably speeds up, more variables to play with.

 

[Drakkith]

Sexual reproduction must have initially been one of those lucky mutations.

Not just one of those lucky mutations, but a lot of "lucky" mutations acted upon by natural selection. That may seem like it's very unlikely to some, and it certainly is, but natural selection had several billion years to build up to that point. Trillions upon trillions upon trillions of fast-reproducing cells and a couple billion years over which to act is a lot of chances.

 

[Jon Richfield]

Not just one of those lucky mutations, but a lot of "lucky" mutations acted upon by natural selection. That may seem like it's very unlikely to some, and it certainly is, but natural selection had several billion years to build up to that point. Trillions upon trillions upon trillions of fast-reproducing cells and a couple billion years over which to act is a lot of chances.

To me that seems to under-emphasise the non-stochastic nature of evolution, "evolutionary opportunism" building upon the nature of what had gone before. (I don't like the use of the term "heuristic" in this connection, because to me that suggests something too teleological).

I suspect that sexual reproduction was a by-product or consequence of the nature of duplication of nucleic acid by chain sequence matching and of cell formation and division at the time when the first cellular life was evolving. I suspect furthermore that it was preceded by phases where cell materials were rather freely exchanged and the concept of "species" was not yet well-defined. (Not that IMO it is all that cleanly defined nowadays, but let that be for the moment!)

 

[Drakkith]

To me that seems to under-emphasise the non-stochastic nature of evolution, "evolutionary opportunism" building upon the nature of what had gone before. (I don't like the use of the term "heuristic" in this connection, because to me that suggests something too teleological).

I'm not sure what you mean by this. Can you elaborate?

I suspect that sexual reproduction was a by-product or consequence of the nature of duplication of nucleic acid by chain sequence matching and of cell formation and division at the time when the first cellular life was evolving.

Sexual reproduction is thought to have evolved around 1.2 billion years ago. Life is thought to have arisen well over 3 billion years ago. Cellular life was around long, long before sexual reproduction evolved.

 

[Jon Richfield]

I'm not sure what you mean by this. Can you elaborate?

"Stochastic" in this sense would suggest that just any mutation in any organism would be equally likely and equally evolutionarily significant, like starting over with a new toss of a hatful of type every time it doesn't come out reading like a page of Shakespeare.
"Heuristic" would be like tossing again mostly the letters that didn't match the page.
Evolution by natural selection is more like the latter, but not much like either, because it is not teleological; there IS NO page to match for a foreknown and desired, or notionally correct outcome. ANY outcome that serendipitously improves successful reproduction rates (ie increases "fitness") represents progress in the short term, though in the longer term it might be disastrous.
So for example, a more muscularly competitive male or one better endowed with an impressive fertilisation mechanism might be the result of advantageous to a male in a particular generation. (It might prove disastrous later, but that is a problem for the teleologist.) But the same mutations might prove useless a hundred million years earlier, when say, muscles or intromission were irrelevant to reproduction.

Does that help?

Sexual reproduction is thought to have evolved around 1.2 billion years ago. Life is thought to have arisen well over 3 billion years ago. Cellular life was around long, long before sexual reproduction evolved.

Good luck; never mind demonstrating that, good luck just stating it meaningfully -- ask yourself what form the original sexual reproduction might have taken!

What do you mean by sexual reproduction? Virile males and complaisant females with functionally conspicuous secondary sexual features to match each gender? Long before anything of the type emerged, before even distinct gametes had evolved in prokaryotes, let alone eukaryotes, the genetic functions of nucleic acid reading for gene expression had existed, and probably even before that, reproduction of nucleic acid chains by base-pair matching. (Think out the information theory of the process!) Even today the expression of genetic information in prokaryotes is not all that well distinguished from reproduction.

Now, what is the essence of sexual reproduction; not the variety and mechanism of genders: it is a variable set of aspects of:

1. Given an organism that has an adequate genome, (typically in the form of paired NA chains, so I'll ignore any other form here, though that is not necessarily the only possibility) the organism can split the paired chains apart for reading, either for expression or duplication. In its simplest form this is "asexual" reproduction, such as in somatic cells or monocellular organisms.
2. An elaboration or in fact possibly a degeneration of that very mechanism could match the paired chains in the organisation of the first approach to chromosomes in the modern sense. This could have been very helpful in permitting primitive, asexual, forms of chromosomal reproduction; cells could thenceforth "tell" whether their own or daughter chromosome complements were complete, in contrast to some viruses such as flu.
3. A separated, but coordinated mechanism would be necessary for cell division, or we simply would wind up with a mass of undifferentiated cytoplasm stuffed with chromosomes or perhaps ancestral forms of chromosomes.
4. Inverse forms of division of cells and matching of chromosomes would lead to the merging of cells and matching of their genetic material. this would amount to a primitive form of fertilisation. Note that a key aspect of this form of combination would amount to the formation of a diploid zygote from two haploid cells or gametes.
5. To correct this condition that otherwise must lead to runaway polyploidy; we need a form of division that would halve the diploid chromosome complement to reinstate the haploid state, and precisely that is what meiosis means: reduction (commonly called reduction division).
6. That is what sexual reproduction amounts to. All the rest, genders, manes on lions, penes in males, special forms of gametes (anisogamy instead of isogamy) are frills; frills arising repeatedly in innumerable forms in response to selective pressures. It is the frills that began to become arguably detectable about 1 - 2 GY BP. Sexual reproduction was something like twice as old at a guess; maybe more.

I have a nasty feeling that I have forgotten a couple of books' worth, but it is a big subject, the realities are speculative, and I suspect that you time is not much less at a premium than mine, so if I have omitted anything disastrously, please let me know.

 

[Ryan_m_b]

General mod note: there's been a lack of references for a while, that was ok when we were covering the very basics but if the thread is trending towards the evolution of specific traits PF rules on citations become more important.

 

[Adamchiv]

General mod note: there's been a lack of references for a while, that was ok when we were covering the very basics but if the thread is trending towards the evolution of specific traits PF rules on citations become more important.

I think that we are dealing with each issue as it comes, this specific issue has become deeper but I think we are on the cusp of resolving it and moving into another sub topic. As the original poster I feel that this is leading very nicely through each specific query. Though I am certainly not the authority on here this is just my opinion

 

[BillTre]

Sexual reproduction is usually considered to have the following cycle whenever reproduction occurs:
1) diploid cells (having two sets of chromosomes) divide to reduce the number of chromosomes to half (haploid)
2) the fusion of two complementary haploid cells to restore the resulting fused cell to the diploid state

Functionally important for this are:
-eukarote chromosomes (linear chromosomes with teleomeres), https://en.wikipedia.org/wiki/Centriole
-pairing of homologous chromosomes to facilitate crossing over,
-cell division mechanisms that ensure the right chromosomes go to the right cell during division
The cell division mechanisms involve centrioles (spindle organizers), a spindle containing microtubules on which the chromosomes move during division and that is involved in cell division, and centromeres on chromosomes that attach them to the spindle so they can be moved to one of the daughter cells.
This is suite of features is found in almost all sexually reproducing organisms, except that some plants and fungi can do without the centrioles.

This is distinguished from the situation in many bacteria, where they have a circular chromosome (which is structurally simpler) and most reproduction involves duplicating the chromosome followed by cell division such that each daughter cell gets a chromosome.
Bacteria can exchange DNA and increase their genetic variability by mechanisms like conjugation, but this is not something that happens every time the organism reproduces and it does not mix whole genomes. It is thus an occasional mixing event compared to sexual reproduction.

Genes genetically linked together on a parental chromosome have the opportunity to break their linkage to neighboring genes and acquire new neighbors. This results in greater diversity in the genetics of the offspring because an important aspect of diversity is in the diversity of different gene combinations.

Most sexual organisms use sexual reproduction whenever they reproduce, however, some cases (such as hydras) can bud off of new organisms in a non-sexual way.
This results in a clonal derivative of the organism's somatic cells. No genetic differences from the parents.
Asexual reproduction can be a faster way to reproduce in a very permissive environment where the organism is thriving, not stressed and apparently doesn't need a genetic recombination to create potentially more adaptive genetic combinations. Asexual reproducers can often also reproduce sexually, in less optimal conditions, so that their offspring are produced with the possible genetic benefits of genetic recombination. Aphids can do this kind of thing.
Some animals have lost sexual reproduction completely (such as Bdellid rotifers and some fish and reptiles).

In animals, the haploid cells are the reproductive cells and the diploid cells are the somatic cells (most of the other cells in the body). In some fungi and plants the relationship is reversed (adults haploid, reproductive cells diploid), but because the above cycle is still used, its still sexual reproduction and results in a greater diversity of gene combinations.

As stated above:

Sexual reproduction is thought to have evolved around 1.2 billion years ago. Life is thought to have arisen well over 3 billion years ago. Cellular life was around long, long before sexual reproduction evolved.

this complex suite of features required for sexual reproduction probably arose in a common ancestor of plants, animals, fungi and protists (single celled eukaryotes). Eukaryotes have linear chromosomes, and a cell division mechanism to deal with them properly.

The original post was about sexual organs, not sexual reproduction, but an understanding of sexual reproduction underlies it.
Sexual organs are there because of the occurrence of sexual reproduction. Sexual organs support the production and survival of the specialized sex cells (internal sexual organs). Sexual organs (external gentalia mostly) are involved in delivering the male haploid genome (sperm in animals) to the female's reproductive cells (eggs in animals) for fertilization. These organs probably evolved later as reproductive mechanisms became more complicated and sex cells in metazoans become more specialized. Early fish-like-things (and some fish today) for example, just released gametes into the ocean where they largely rely on chance to find and combine complementary gametes. The delivery system is minimal, but the cells still reside in testes and ovaries.

 

[Adamchiv]

There is certainly enough detail in these previous posts to form a detailed understanding, I thank you all for such in depth analysis, it will take me a while but I think I can find some foundation there for sure. Could we discuss (and this may sound crude or silly) the mental stimulation involved in evolutionary reproduction, for example, I can't think of which animal it is but there are animals that are dying out because they don't want to mate. So first question is why do they lose their libido, second question is regarding stimulation, to get to a positive stimulation in reproduction is that trial and error? For example those that got a positive stimulation were more likely to reproduce? Because it doesn't exactly feel horrible does it and there are obviously very positive urges that can't have just "been" it must have been an evolutionary trait right? Hate to get into these crude things but again its part of the whole development of life without any conscious design that I would really like to understand