How does the Theory of Evolution explain the beginnings of sexual reproduction?
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It is a major puzzle, no one is quite sure. See the attached article for more details...
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"Ontogeny recapitulates phylogeny."\n\nWhich is a fancy way of saying that the stages an organism goes through during gestation (pre-birth) mirror (to some extent) its evolutionary history.  There are stages when even a human fetus resembles more a fish or an amphibian than a mammal, and we all start out as a single-celled organism.\n\nMost species' evolutionary history is educated guesswork based on similar anatomical and physiological structures, compared with both existing organisms and those in the fossil record.  Also, DNA similarities indicate evolutionary proximity -- for example, aside from the fact that all primates look similar (similar anatomical structure) our DNA is closer to that of certain monkeys than any other species.  This strongly suggests that somewhere back in history we had a common ancestor.\n\nBy the way, anyone who discards the theory of evolution because it's "not proven" doesn't know the first thing of how science works and, to be honest, should be ignored.
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Evolution is a theory developed by Charles Darwin to explain the creation of life. \n\nHe believed that man originated from a single-celled organism that combined with another single-celled organism to create the first dual-celled organism.
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Darwin's Theory of Natural Selection, in a nutshell:\n\nThere are three observations about life\n1) Variation: Individuals of a species are not all identical.  \n2) Competition: More individuals are born than can possibly survive to reproduce.  \n3) Inheritance: Individuals pass on traits to their offspring.  \nGiven these three things, those individuals in a species that have traits that help them survive better and produce more offspring, will pass those very traits on to those offspring.  So in this way, beneficial traits become more frequent a population, and produce an overall change in the species over time.  \n\nThat's it.\n\nAs for the creation of new species:  If two subpopulations of a species get separated for long enough, then they will change in separate directions, and will eventually lose the ability to interbreed, resulting in (now) two separate species that will continue to change (evolve) in different directions.\n\nThe catchphrase "survival of the fittest" summarizes this idea ... but use it with caution.  It's not just about "surviving" but "surviving to reproduce."  For example, a peacock's tail doesn't really help him "survive" better ... in fact it probably makes him an easier prey for predators ... but it does attract the ladies.  So it makes those individuals with the flashiest tail more "fit" then their homelier cousins.\n\n-------------- A warning about 'tiffany g's answer ---------------\n\nBe careful with answers like 'tiffany g' who copy-paste web pages instead of giving you a link to them, and without giving you the source, so you can check it out.  She is copying from the web-site allaboutscience.org, a thinly disguised Christian/Creationist site.  \n\nMy objection is not with people presenting the Creationist side ... but rather the attempt to hide that fact.  For example, it is deliberately misleading for a site to call itself "allaboutscience.org" when it does not address science topics in general, but only topics like the Big Bang, Evolution, and evidence for the existence of Jesus.  (Watch out for "allaboutphilosophy.org" as well.)\n\nAs a glaring example of intellectual dishonesty, the citation/page finishes with Darwin's famous quote about the eye ... famous because it is always quoted out of context and omits Darwin's very next sentence.  Darwin did indeed write that the evolution of the eye "seems, I freely confess, absurd in the highest degree."  (Note the word "seems".)  But then Darwin continues ... "Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real."  (See second source, Darwin, Ch. 6.)\n\nIn other words, Darwin immediately refutes the "irreducible complexity" argument, by pointing out that all we need to do is show that the eye can come about through small, incremental changes that each confers a small advantage, no matter how small.  Every single case of "irreducible complexity" yet offered by Creationists has always been shown (usually quite easily) to be fully "reducible."\n\nCreationists love to quote out-of-context from Darwin's Chapter 6, because this is the chapter where Darwin considers possible objections or "difficulties" with the theory, and then refutes them. The Creationists love to quote Darwin's own-words description of the "difficulty", but then omit his
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It was probably a single celled organism and it didn´t involve sex as we are used to. Instead they would have exchanged genetic material to produce an offspring that was different from the parents. \n\nSex was "invented" about 800 million years ago. Before that everything reproduced through mitosis. There was some multicellular organisms at the time, animals even, but they also reproduced with mitosis. Mitosis is basically cloning. The offspring is a carboncopy of the parent leaving little room for changes which is why life on earth was very primitive for 3 billion years. But 800 million years ago an explosion in the biological diversity occured. Life went from simple organisms to dinosaurs in a flash. Two things contributed to this explosion, called the Cambrian explosion. \nOne was the oxygenation of the atmosphere and the hydrosphere which had been going on about 2.5 billion years but had now reached levells where life forms were able to fully utilize this resource. \nThe second was the advent of sexual reproduction which always generates offspring that is different from the parents causing evolution to go berzerk.\n\nWhich lifeform that actually was first we can´t really say. There are organisms today that can reproduce both sexually and asexually so the fossilrecord can only give so many clues. We can only say that suddenly, by geological timescales, there were lots of advanced lifeforms on earth that used sexualreproduction.
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Theory of origin states that DNA can lead researchers to a specific date that the first of a species originally occured. Natural selection deals with the process by which random generation of attributes help one animal to survive and not another, thereby selecting on of the two to procreate. The two theories are not really related in a way that you can contrast them, as they deal with separate subjects, not arguing ones.
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Evolution of reproduction. Nature finds its way.
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You spelled it wrong...\n\nAccording to the Garstang Hypothesis, development of sexual maturity in a non-metamorphosing lineage of tunicates might provide the immediate proto-chordate ancestors of more typical chordates such as Amphioxus (Subphylum Cephalochordata), or even of early Vertebrata (Ostracoderms) as shown here. Development of sexual maturity in a larval form is an example of Progenesis (Garstang called the process Neoteny, which today is used for a different but related differnetial growth phenomenon).
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See the Endosymbiont Theory. Basically, early symbiosis between the two types of organisms, and DNA transfer from one to the other.
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I wouldn't say that I'm anymore intelligent than someone else, but I did want to answer your question, so....\n\nYou are confusing the theory of evolution (diversification of species) with the theory of abiogenesis (life from natural compounds).  That's okay, many people confuse the two.\n\n1.  How did life get from soup to single-celled organisms?  From wikipedia, "J.B.S Haldane suggested that the earth's pre-biotic oceans - very different from their modern counterparts - would have formed a "hot dilute soup" in which organic compounds, the building blocks of life, could have formed.\nIn 1953, taking their cue from Oparin and Haldane, the chemists Stanley L. Miller and Harold C. Urey carried out an experiment on the "primeval soup". Within two weeks organic amino acids, the basic building blocks of life, had formed. While Miller and Urey did not actually create life; they demonstrated that a more complex molecule — the amino-acids — could emerge spontaneously from simpler chemicals, in the presence of an external energy source in an atmosphere largely devoid of oxygen (the experiment involved shooting a spark, representing lightning, into their flask of supposedly primitive earth-gases)."\n\n2.  How did the original cell eat and develop asexual reproduction?   You are putting the cart before the horse.  In order to get to the cell stage, self-replicating molecules had to exist first... i.e. reproduction & "nourishment"  was occurring well before the cell stage.  Also, what are you referring to with "nourishment"?  For a self-replicating molecule, nourishment would consist of other molecules that it could combine with to form more of itself.\n\n3.  In the "soup", how did primordial cells develop resistences?  Resistence to what?  I don't understand this question.  To the environment?  To viruses or bacteria?  You need to elaborate here, I'm sorry.  I think it ties into your next answer, but not sure.  Please read my answer to #4.\n\n4.  How did it evolve everything it needed if it wasn't in it's DNA?  Can you give an example?  Hmm.  I'm trying to understand how you are approaching this question.  Let's say you have 100 little cells, each a little different.  5 cells can withstand a higher water temperature than the others because of a mutation they have.  One day the temperature goes up and kills off the other 95 cells.  That only leaves the 5 with the mutation.  They scamper off and reproduce like crazy... the cell strain has just evolved a little.  Now repeat this a gazillion times with a dynamic interacting environment and there you go.
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These two processes are mechanisms that increase genetic diversity in organisms that reproduce by sexual reproduction.
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The hen, or the ancestors of the hen, had to come first. The mode of reproduction would have evolved later when the original mode of reproduction became dangerous to the parent's health, or just more convenient.\n(please don't flame me for this; most of the Theory of Evolution is proven to be true in that humans are taller than they were a hundred years ago, immune systems learn to fight off diseases, many different species have split from one, etc.)
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asexual reproduction doesn't require two partners in order to reproduce...sexual is the opposite.  It requires two creatures of the opposite sex in order to reproduce.
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The theory of evolution (assuming you are lumping this in with the physics of the creation of matter) has the same initiation problem as the Religious one.\n\nWhere did the first matter come from?\nWhere did God come from?\n\nBoth 'sides' will say there has simply been [insert your object here]\n\nPeace out
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Asexual reproduction\n\n\nAsexual reproduction is the biological process by which an organism creates a genetically-similar or identical copy of itself without a contribution of genetic material from another individual. Bacteria divide asexually via binary fission; viruses take control of host cells to produce more viruses; Hydras (invertebrates of the order Hydroidea) and yeasts are able to reproduce by budding. These organisms do not have different sexes, and they are capable of "splitting" themselves into two or more individuals. Some 'asexual' species, like hydra and jellyfish, may also reproduce sexually. For instance, most plants are capable of vegetative reproduction—reproduction without seeds or spores—but can as well reproduce sexually. Likewise, bacteria may exchange genetic information by conjugation. Other ways of asexual reproduction include fragmentation and spore formation that involves only mitosis.\n\n\nSexual reproduction\n\nSexual reproduction is a biological process by which organisms create descendants that have a combination of genetic material contributed from two (usually) different members of the species. Each of two parent organisms contributes half of the offspring's genetic makeup by creating haploid gametes. Most organisms form two different types of gametes. In these anisogamous species, the two sexes are referred to as male (producing sperm or microspores) and female (producing ova or megaspores). In isogamous species the gametes are similar or identical in form, but may have separable properties and then may be given other different names. For example, in the green alga, Chlamydomonas reinhardtii, there are so-called "plus" and "minus" gametes. A few types of organisms, such as ciliates, have more than two kinds of gametes.\n\nHumans, most animals, and plants reproduce sexually. Sexually-reproducing organisms have two sets of genes for every trait (called alleles). Offspring inherit one allele for each trait from each parent, thereby ensuring that offspring have a combination of the parents' genes. Having two copies of every gene, only one of which is expressed, allows deleterious alleles to be masked, an advantage believed to have led to the evolutionary development of diploidy (Otto and Goldstein).
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Darwin's theory of evolution has four main parts: \n\n1. Organisms have changed over time, and the ones living today are different from those that lived in the past. Furthermore, many organisms that once lived are now extinct. The world is not constant, but changing. The fossil record provided ample evidence for this view. \n\n2. All organisms are derived from common ancestors by a process of branching. Over time, populations split into different species, which are related because they are descended from a common ancestor. Thus, if one goes far enough back in time, any pair of organisms has a common ancestor. This explained the similarities of organisms that were classified together -- they were similar because of shared traits inherited from their common ancestor. It also explained why similar species tended to occur in the same geographic region. \n\n3. Change is gradual and slow, taking place over a long time. This was supported by the fossil record, and was consistent with the fact that no naturalist had observed the sudden appearance of a new species. [This is now contested by a view of episodes of rapid change and long periods of stasis, known as punctuated equilibrium]. \n\n4. The mechanism of evolutionary change was natural selection. This was the most important and revolutionary part of Darwin's theory, and it deserves to be considered in greater detail. \n\nhttp://www.globalchange.umich.edu/globalchange1/current/lectures/selection/selection.html
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you seem to be so smug in your belief of evolution.  there is no proof whatsoever of it happening.  adaptation is different.  bacteria becoming immune to antibodies is adaptation.  humans do this all the time.  the bacteria aren't changing into anything different, they are still bacteria.  \nthere is no evidence in the fossil record either to support your idea.  in fact, all evidence in the fossils says otherwise.  there is no common ancestor of humans and primates.  nowhere.  lucy was an oversized chimp.  neanderthal man is equivalent to modern man in brain capacity, body structure, and everything else, what's the difference?  you can't use the tooth of a pig to create an entire skeleton of a human, that is called fraud (piltdown man).\n\ntry these FACTS: dr. frederick hoyle did a study on the probablility of a single-celled lifeform through means of random process from the beginning of time.  the likelihood of this happening is 1 in 10 to the 40,000 power.  (anything over 1 in 1050 is considered scientifically impossible).  hoyle stated, "evolution is nonsense in the highest degree"\nthe co-discoverer of DNA, francis crick; did a similar study on the chance of one single strand of DNA happening by random chance, but the results came that the chance is so small that it is nonexistant (so close to zero it's actually there)\n\nthe alternative? intelligent design.  all evidence points to a young earth.  if the earth is millions of years old: why hasn't it stopped spinning yet?  it slows down every year?  why hasn't the sahara desert taken over the plant yet?  it's growing by the day?  why have we never seen a single star form?  why hasn't the moon left us yet?  it gets farther and farther away every year?  \n\nother science would ask: why do some heavenly bodies rotate counter-clockwise if they all resulted from the big bang?  (according to the LAW of angular conservation, they should all be spinning the same way)  why isn't there a huge vacuum (present after any explosion); but the universe is instead expanding?  (refer to newton's LAWs of relativity)  why would the population curve put the start of humanity at about 4500 years ago, if we've been around for millions?  why is the oldest tree (also the oldest living organism) only 4500 years old?  \n\nuse evolution to explain morality, emotions, intelligence, abstract thought, love, etc.  you can't.  the only plausible answer is intelligent design.  \n\nanthony flue, once the greatest known and most highly revered atheist; writing over 30 books on the subject is an oxford double-doctorate with numerous other degrees and awards.  now a theist.  the clincher?  intelligent design.  unless you think that you're smarter than this guy (and it doesn't look like it from your grammar, spelling, and theology)  study a bit more before you go bashing theists.  \n\n"when science finally comes to the top of this mountain of truth, it will see that religion has been there all along."