Can natural selection explain the origin of poison for killing one's prey. The snakes (and all reptiles) preceeded birds and mammals on the evolutionary scale of complexity.  That being the case, how is it possible that it developed the ability to kill mammals and birds with poisonous bites? What is the specific mechanism that would explain how snakes, presumed to be earlier on the evolutionary timescale, develop poisons as a way to kill for food, and develop the substances necessary to enable them to eat and digest the birds and mammals, animals  that came into existence much later on the timescale?
120015
First off: THERE IS NO SUCH THING AS AN EVOLUTIONARY SCALE OF COMPLEXITY. The idea that the beings can be ordered from bacteria to human belongs in the 18th century.\nThere were both birds and mammals around in the Mesozoic Age, when snakes evolved. And the first snakes were similar to boas, not venomous ones; the colubroids (the group that includes the venomous forms) are first recorded in the Miocene (that is Tertiary, long after the diversification of modern birds and mammals). Therefore, you are starting from a false premise.\nAlso, salivary glands are present in all tetrapods, and especially in amniotes (reptiles, birds and mammals). Saliva possesses enzymes, and it's not that difficult (from a biochemical or evolutionary viewpoint) that any mutations that changed those enzymes into other more toxic ones were retained because of their advantage when subduing prey. Indeed, the evolution of venomous saliva did not happen once: Gila monsters and at least some insectivorous mammals also have similar (but independently evolved) systems.  \nThus:\n- snakes did not precede birds and mammals\n- poisons are made of enzymes, and all enzymes can be "poison" to some living being or other (ask the bacteria that are killed by the saliva in your mouth!)
112250
Darwin's theory of natural selection is that 1) More individuals are born than can survive 2) Variation in the population (due to mutations) makes it so some individuals are more fit than others 3) This (phenotypic) variation is (genetically) inheritable 4) The individual survives to pass their genes onto the next generation. Lamarck's idea of use and disuse simply says that acquired characteristics (phenotypic) over the course of a lifetime are then passed on to offspring (genetic). For example, giraffe's long necks are caused by the constant stretching for food higher in the tree, and every generation therefore would see the neck getting slightly longer.
618836
No, i think it also has something to do with strenght. Also it has something to do with the suroundings, if you have time to buy poison why not?
156265
Micro-evolution is when a plant or animal varies from the statistical norm of the species in some way that causes it to have an advantage over the other members of it's species in the particular environment in which it happens to be located.\n\nThis can be a result of mutation, however generally it is simply the result of the normal variations within a group of plants or animals since most every mutation is not beneficial but either benign or harmful.\n\nFor instance if greater size allows an animal to fight off predators or run faster then the other members of it's species then it will have a greater chance of reproducing and the species will tend to "evolve" into a larger species.\n\nThat micro-evolution can occur is clearly demonstrated by examining the different breeds of dogs that have been artificially altered by the selective breeding that has gone on according to the preconceived plans of dog breeders.\n\nMacro-evolution is an entirely separate although similar premise. According to macro-evolution an ameba like creature can become a multi-celled creature that can develop complex internal organs and nervous systems and external organs like eyes and ears. It doesn't stop there though. It claims that a fish can become an amphibian which can become a mammal and that one species of animal, like a monkey can somehow have it's genetic code altered at the microscopic level millions and billions of times over in a beneficial way resulting in an intelligent human being.\n\nScientists who have worked out statistical models of the chances of such a thing happening have estimated that the odds are something like 10 to the 250th power against that scenario. They say that anything with odds over 10 to the 10th power, that is (ten billion) 10,000,000,000 to 1 are generally considered to be outside the realm of what is possible to happen without some external factor being the cause.\n\nhttp://web.express56.com/~bromar/
113669
Wow, 5 people responded before me and never really answered your question.\n\nThe main question you asked was about "complex animals" compared to land plants. You were understanding this right.  Remember that those early plants were more similar to modern bryophytes (like mosses, liverworts and hornworts).  The vertebrates at that time were all sea creatures (very primitive fish-like).\n\nBy the time the land vertebrates appeared, large trees were abundant and so were insects.\n\nAlso, why do some people insist on using a book that says insects have 4 legs and calls bats birds as their science book?
517035
One piece of advice: Try asking more directional questions rather than a title question.\nTheory of natural selection is a model for explaining the mutational changes that species go through in nature by the pass of time. Even Darwin had to go through guess work when he had to talk about the origin of species.\nThe strongest evidence nowadays about the same ancestory you asked for is the DNA. well if you analyze the DNA of the magpie the crow, human and a bacteria together they are roughly all the same let's say at least 90% of it are alike. So one can deduce that maybe one day they were all oroginated from a single molecule as a start but went through different mutations to form different kinds of species in time
148130
I don't think it's really possible to know that without testing it. But I would guess that your idea is right, because there would not be enough venom to kill an animal that large. It would probably make it sick. But then again, a whale, or any other really large animal, would react differently to the venom. It might kill it despite the size.
352740
This goes right back to a basic body plan for most animals going throughout evolution.  (A lot of this I got from Richard Dawkins, Ancestor's Tale.)\n\nThe basic body plan for most animals is a tube, with one end for feeding, and the other for excreting.  It then becomes useful to have all the senses at the feeding end, as the senses are helpful for finding food (and not needed at all for excreting).\n\nAnd then, as the nervous system gets more sophisticated, it becomes convenient to have the ganglia, and later the brain, near the main sensory organs.  This reduces the length of vital nerves from the sensory organs to the brain.  (E.g., if your brain was in the most protected part of your body, your abdomen, then think of how long the optic nerves would have to be from your eyes.  Not only does this cause a delay in signal transmission, but it increases the odds of damage to the optic nerve.) \n\nFast forward a couple of billion years, and this tube body plan hasn't changed much.  Sensory organ snear the feeding end, and brain near the sensory organs.  Humans are no different, except that they stand upright.  \n\nBut even then, it is advantageous to have our sensory organs perched as high up as possible, and again, to have the brain as close to these sense organs as possible in order to shorten the distance that sensory impulses have to travel.
489209
I was taught that the snake/serpent was changed when cursed by God to from then on it had to crawl on its belly and eat dust.  All of creation changed after the fall.\n\nOf course this particular serpent was Satan, but the animal he used to represent himself was cursed as well.\n\nGen 3:14 So the LORD God said to the serpent, "Because you have done this, \n       "Cursed are you above all the livestock \n       and all the wild animals! \n       You will crawl on your belly \n       and you will eat dust \n       all the days of your life.
468029
One of the most significant changes that occurred in early vertebrate evolution is that of the development of jaws.  Jaws first appeared generally in gnathostomes, but more specifically in shark like ancestors called placoderms. Present day sharks are the representative group of early vertebrates with jaws. \n\nThere are two theories on why jaws first evolved. One theory ("new skull") states that jaws evolved to aid in more efficient feeding and feeding on larger prey, which increased metabolic rate and thus allowed for a more active lifestyle. The other theory, "new mouth", states that jaws evolved to allow for more efficient ventilation mechanisms, which allowed for a higher metabolic rate and thus a more active lifestyle. Secondarily in this scenario, jaws also aided in more efficient feeding.\n\nAlso, it should be noted that many animal groups that evolved prior to the early vertebrates has pharyngeal slits or pharyngeal openings. That isn't really a characteristic specific to vertebrates as several pre-chordate and chordate groups have pharyngeal/gill slits.
575013
It's not entirely believable that we evolved from apes. If you have ever actually looked into the question you would know that animals do evolve. I'm a Christian and still don't refute the facts that "survival of the fittest" is an actual scientific process. People don't evolve from ants because they have an entirely different make-up than people. Ants have an exo-skeleton while mammals do not. One good example of things evolving are moths. During the industrial revolution in Europe many objects (trees) became covered with a light soot. The moths used to be able to camoflauge themselves on tress but couldn't anymore because of the soot on the trees. Survival of the fittest was demonstrated because all of the darker moths that blended in with the trees were not eaten by preadtors. When these dark colored moths began surviving they reproduced and their offspring were well-suited to their environment due to their dark color. Evolution can not be denied. How can you explain how some animals must be "2 sexes" so that they can ensure their population can continue? It's obvious that at one time those types of animals were either male or female and had to "evolve" to survive. The whole theory behind evolution is: "Those that are best-suited to their environment will survive." Maybe not all monkeys had problems with predators as others did, which means they had no reason to evolve. Darwin broke-it down very easily and demonstarted a gradual change that developed us into humans.
141612
My theory: Early humans needed to warn others about danger, so an uncontrollable scream helped alert their "clan" of danger. People who didn't scream were killed by the danger.\n\nThis is JUST my theory, I'm not commenting one way or another on evolution.
332367
The first answer was comprehensive but doesn't answer the question you asked "why would it have to be poisonous?"\nThe answer is that it doesn't *have to be* poisonous, it just is. The argument is circular: the plant is successful and grows well because it has no predators that want to eat it and because it has no predators it grows well ... The poisonous principle is what is called secondary product; it is something that arose in the plant (perhaps as a metabolic byproduct and, because it was advantageous to the plant, it persisted.
220103
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.
409613
Every fossil, every observation in biology points to evolution. There is nothing that goes against it or points to a different way to scientifically explain modern diversity. There is not one fossil or one piece of DNA that does NOT point to evolution.\nCreation relies on a lot of belief and the ability to dismiss all the known evidence, since ancient Greece to the present time, in the case for evolution.\nEvolution, on the other hand, keeps presenting solid evidence, regardless of those who believe otherwise. \n\nHere is a theoretical example of natural selection and adaptation.\n\nSay you have an island, about twenty miles from any other island, where there is a species of bird, say finches. In any population of birds, there is going to be a variety of beak sizes and wing sizes, (like nose and ear size, and height variation in humans), suddenly there was a drought, lasting several years, and the main food source of the finches, say, sesame seed, was destroyed, and all they had to eat was wheat, which is harder to break and eat than sesame. \nWhat characteristics would give one bird an advantage over another? Those with smaller beaks would have more difficulty cracking the wheat and feeding it to any baby birds, therefore they would have less live young. Those with largeer, stronger beaks would crack and eat more wheat and have more live young. Chances are, that their offspring would have, on average, larger, stronger beaks than those of small beaked finches. The stronger your beak, the more you eat, the more children you have. \nSo what other characteristics? Those with stronger, larger wings could try to find other food, but if they can't make to the other island, they die, those that make it to the other island, and if it has food, will have, on average, larger wings than those that didn't make it. They wil have more children, who, on average, will have larger wings.\nThese are simplified examples, it is more complex than this, but the basics are there.\n\nAnother, real life example is the Peppered moth.\nHere is the Wikipedia link\nhttp://en.wikipedia.org/wiki/Peppered_moth_evolution\n\nThis is evolution at work.\nRead more about evolution, but do it with an open mind. It wiil be of no use looking at evidence if you have already decided to reject it. Remember, you are doing science, at that is what scientist do. The more you read, the more you will understand. Try "Origin of Species " by Charles Darwin as a start, or try Google for a summary.\n\nGood luck to you.
56616
OK, first things first. \nThe anaconda (Eunectes notaeus) is a South American aquatic constrictor boa. \nPythons are Asiatic/African constrictors (mostly arboreal); they belong to a different subfamily (some authors even assign them to a different family) from South American boas. \nThe evolutionary history of the family Boidae (in a broad sense, i.e. including both these groups) is a very interesting paleontological issue; their phylogenetic (ancestral-descendant) relationships are still being discussed. \n\nAs the original question is not clear, I'd like to know if you're interested in the evolution of a particular species or the Boidae in general. \nHere's two links to papers on snake phylogeny, including the Boidae \nhttp://www.kingsnake.com/aho/pdf/menu2/slowinski2002.pdf\nhttp://evo.bio.psu.edu/hedgeslab/Publications/PDF-files/67.pdf\nI'll check back :-)
400942
It's quite possible.  I saw a tv show a while ago where a lioness (an animal which generally weighs less than even a baby elephant) survived a bite by a cobra, but a bite to a baby animal might be worse since its immune system is less well developed.  \n\nIt would really depend on how much venom got into the animal's system.