How have dolphins evolved through the millenia?
341496
This will knock your socks off.  Whales and dolphins share a common ancestry with ... hippos!  (This is not a joke answer.)  Even Richard Dawkins was surprised by this ... "What is shocking is that, according to the molecular evidence, whales [and dolphins] are deeply embedded *within* the even-toed ungulates. Hippos are closer cousins to whales than hippos are to anything else including other even-toed ungulates such as pigs."\n\nIf nothing else, keep in mind that whales and dolphins are mammals, and thus evolved from land animals.  Based on genetic evidence, it seems that pigs and ruminants split about 60 million years ago (mya), and hippos split off from the ruminants about 55 mya.  The whales split off very soon afterwards at about 54 mya, with the semi-aquatic 'Pakicetus' appearing about 50 mya.  Toothed whales (including dolphins) and baleen whales split from each other about 34 mya.
131055
I'd like to think that you're asking this question with an earnest wish to get good informative answers. If that is the case, I invite you to see the link that Kurdiatcha left, or to do a web search for the term, or else, to read some good Evolution textbooks such as Ridley's "Evolution" or Freeman & Herron's "Evolutionary analysis", or Futuyma, or Stephen Jay Gould if you want something more entertaining.\nIf that is not the case, I'm not bothering anymore *sigh*
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There are two theories to explain how the Platypus has evolved into what it is today. The first (theory B) shows that relatives of monotremes formed their own evolutionary branch that was completely different from development of both marsupials and placentals. This change is thought to have occurred 135 million years go, the beginning of the Cretaceous period. The marsupials and the placentals divided at some point 135-65 million years ago.\n\nThe Second (theory A) was proposed by Gregory (1947) and was not popular until the 1970s. He said that between 135-65 million years ago, the placentals and marsupials separated to their own way then later the monotremes and the marsupials went their own way.\n\nEvidence for this theory is that the reproductive systems of monotremes and marsupials are extremely similar. The embryos of both have some stage of encased shells in the gestation period. The only difference is that monotremes have the encased shells throughout the entire gestation period, whereas marsupials only have the encased shells for about two thirds of the gestation period.\n\nAre you denying that evolution exists at all?
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Evolution is one of those very dangerous subjects in which just knowing the surface of the subject can be misleading.  Humans did not evolve from monkeys.  We evolved from the ancestors of current apes.  Think of it like a fork in the road.  The apes took their path, and we took ours.  And all evidence does point to Darwin's theory of natural selection being correct.\n\nEdit:  To those of you saying that evolution only occurs over thousands of years.......this isn't necessarily true.  Over the last 50 years bacteria have evolved to become antibiotic resistant.  Since bacteria reproduce on a much shorter time period and they don't have the DNA repair mechanisms that eukaryotes have, their DNA mutates much more rapidly than ours.\n\nAlso, monkeys will NOT eventually evolve into humans in 1000 years as one person claimed.  Humans are not the tip of the evolutionary tree as some would like to think; we are just another branch on the evolutionary bush.
452784
One might answer: how did Dolphins discover humans?
20041
Some believers in ID believe the earth is around 6,000 years old. \n\nAre you trying to make a parallel that something can have a designer, but still continue to improve and change under the care of its designer or due to environmental factors? \n\nMyself, I believe in micro evolution. Species adapt within certain parameters because of natural (or not-so-natural) selection. A dog, for instance, can be like a chihuahua or a great dane, but it's still a dog.\n\nI need more convincing to believe in macro evolution. Species changing into other species, etc.
1106753
they evolved to become homo
507131
Evolution is the result of natural selection acting upon random genetic changes.  We evolved to have large brains because they enabled us to out-compete other animals for environmental resources.  The animals with less able brains had fewer offspring while we had more.  It seems that our brains are engineered for problem solving and cooperating with other people.  \n\nAt the same time and in the same environment, other animals were succeeding by developing other abilities.  For example, antelope survive by running fast.  Ants survive by being small and numerous.  Dung beetles survive by eating stuff that most animals don't want.\n\nEvidently, sharks don't need larger brains.  They succeed by being able to swim fast and having sharp teeth--lots of them!  Also, the fact that sharks have existed for 200 million years does not mean that they have not evolved.  Other fish may have evolved from them to take advantage of ecological niches that sharks do not.  (I don't know whether that is the case with sharks, but certainly, other organisms have done this.)\n\nAlthough sharks aren't that smart, other ocean animals are.  Dolphins are extremely intelligent, at least as intelligent as chimps.  Octopuses are very intelligent and have extremely large brains for their body size.  A two-year old octopus, which is elderly for octopusses, can solve the same problems as a two-year old human.  One wonders what things would be like if their lifespans were as long as ours.\n\nAn even better example of an unchanged organism is the brachiopod (clam-like animal) Lingula.  It has remained unchanged for nearly 600 million years.  It lives in a very unfavorable environment--dirty water with little oxygen.  Apparently, it is so well adapted to that environment that no other organism can displace it.
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Heh.  Depending on who you ask, it HASN'T changed.  Let's break it down:\n\nThe names given in Latin for animals are usually just the most specific part of their scientific classification.  Now originally the whole classification system was just set up so you could tell animal A from animal B, so it involved a bunch of branching questions you might ask and then refer to the animal to see in which classification it belonged.  This was a pretty good idea at the time, because with only one name for each type of animal and a systematic way of determining such things, everyone could talk about the same things.\n\nA wrinkle was introduced as biology developed as a science.  With the advent of evolution, and confirmed with DNA sequencing and the like, it was discovered that the classification system that was (almost) haphazardly put together just to sort animals was actually pretty descriptive of common ancestry.  Animals that had a lot in common probably shared recent common ancestors, and animals with less in common were more distantly related.  This eureka of how an accidental classification system could correspond so closely to molecular evidence is still one of the most compelling justifications for the evolutionary theory today.\n\nThe problem is that the correspondance wasn't perfect, and that even now new connections are be found and old ones are being discredited.  So while the old chart was (more or less) static, scientific classifications these days not only change, but are argued about, changed back, and sometimes just not accepted by some experts.\n\nThis is the case we have with the family 'Sulidae'.  This family includes all the birds that are generally referred to as gannets and boobies.  About this, at least, there is no argument.\n\nNow, it used to be thought that pretty much all existing species of Sulidae came from just one group of ancestors.  The Sula.  You see this kind of similar naming crop up a lot in taxonomy, especially when the groups are small but distinct.  In addition to the still-living Sula, there were also any number of extinct fossil groupings which did not survive.  All these groups which made up the family of Sulidae are each called a 'genus', and their names are the first part of the Latin name that animals are commonly referred to.\n\nThis old model of how things happened is now (largely) superceded by a new one.  There are now thought to be THREE living genuses:  Morus (all the gannets), Sula (almost all the boobies), and Papasula (which has just one species - Abbot's Booby).  So basically most biologists have decided from the evidence that three of the ancient groups survived instead of just one, and they did so probably on the basis of fossils that have been found, DNA evidence, and the like.\n\nBut some do not agree with this decision, so you'll actually still see references to both 'Sula bassana' and 'Morus bassanus'.  The second name, that of the species, is really the same name... it's only different between the two because of the rules of Latin grammar.\n\nHope that helps!
279116
Several billion years ago, the first simple amino acids formed crude proteins and RNA to act as simple genetic coding. Over time, these nondescript organisms evolved into bacteria, then photosynthesizing bacteria. Eventually they evolved into simple invertebrates capable of sexual reproduction, and through tweaking of the ovulatory cycle, were able to lay fertilized eggs outside of their body. These invertebrates became fish, then amphibians, then reptiles, then birds. From those birds evolved the ancestor of the chicken which after 4 billion years of evolution was already capable of laying eggs.\n\nThe end.
1135377
You have to look at evolution as a series of slight beneficial changes that are passed down through generations.  The steps from single to double circ are unknown to me, but it is more than a single big jump.
216851
probably it evolved from seaweed.  and as seaweed eveloved it became grasses, and trees, and plants,and from it all of the vegetaion we see today.
752195
Polar Bears:\nFor evolutionists:\nFirst of all, Polar Bears evolved from Brown Bears that where seperated from the other populations by a glacier or possibly something else, trapping them in extreem conditions.\nNow, due to these conditions, pressures where quickly placed on them to have them evolve very rapidly into the Polar Bears (by evolutionary standards, meaning it still took several thousand years), due to the fact that the very harsh conditions quickly weeded out Bears that where not so readilly able to survive.\nNow, the Bears eventually managed to adapt to the conditions, and find an abundant source of food on the sea ice, consisting of Ringed Seals, and ocasionally some other species of seals, such as Walrus cubs.\nAnd, since Polar Bears evolved up North in this area, they obviously couldn't have started down in Antartica.\n\nNow, the Polar Bears have no method at all of travelling this far south, to reach Antartica, as they would die of heat exhaustion far before then, not to mention they would probably lack any prey item, being used to hunting seals, and such.\nAnd, for the Brown Bears that could have theoretically moved down South, and then go their, and evolve into a Polar Bear-like animal (though, it would probably have multiple distinguishing features, and quite probably a different diet), this is also very unlikely.\nThe furthest south that the range of Brown Bears has ever been is in Northern Africa, in the form of Atlas Bears, which have been hunted to extininction by Humans in the eighteen hundreds, which is still quite far away from Antartica.\nNow, even if they theoretically wheren't hunted to extintion by Humans, and where given the time to be able to travel all the way South to the southern most tip of Africa, they would from their be unable to swim far enough to be able to reach Antartica, and would theirfore still be unable to reach it.\nAnd, if you mention the fact that their are marsupial fossils their, then I will have to mention the fact that know placental animals where down South during those many long years ago before Antartica split off, theirfore they still wouldn't have been down in Antarctica.\n\nFor the Creationists:\nPolar Bears have a yearly "routine" of waiting during the sumer for the sea ice to freeze, and, then, when the sea ice does begin to freeze, they then swim out to it, and begin their hunting of seals on the sea ice, never traveling out onto the permanent ice, but only on the temporary ice, as, this is the only ice they are able to hunt on, concidering they hunt by smashing a hole in the ice, and waiting for a seal to surface to take a breath, and then pull it out, and the permanent ice would be much to thick for that.\nAnd, in Antartica, it would have to instead then wait down South, where it is colder then it may be up north, or just as cold, meaning that because the Bears are being inactive trying to conserve energy, they may freeze, and theirfore need more insulation.\nHowever, then they would overheet while hunting, etc, out on the sea ice, which is something that should not happen, and may overall cause some stress, etc.\nSeeing all of these problems and different adaptations the Polar Bears would need to be able to survive in Antarctica, god decided not to put Polar Bears there, as they would likely be unable to survive without having to have a variety of modifications made.\nAnd, this would also be rather inconsistant with the general pattern of dispersal; only marsupials where put on the southern land masses (and placentals eventually invaded the ones they could reach, and then out competed the marsupials wiping them out...and in the case of Antarctica, couldn't survive the extreem cold), which is why they are only found on Australia, and some islands such as Tasmania, and then the Opposum mananaged to survive the "placental invasion".\nThe Polar Bear, being a placental, would have gone against the general distribution of animals a
266328
Hey try this site from the BBC. It might be a little too in depth for you but the first page is a good introduction and page 5 gives a good example on how horses have evolved.\n\nhttp://www.bbc.co.uk/schools/gcsebitesize/biology/variationandinheritance/3evolutionrev2.shtml
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Dolphins are born after a gestation period of 12 months. They are weaned at 9 months and become able to breed at the age of 8 years. The female dolphin will have one baby each year until she stops all breeding at the age of about 14 years. Life expectancy is 25 - 35 years.
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The earth is 4.6 billion years old. The sun is close to 5 billion. Liquid water did not exist on earth until about 4 billion years ago. Life seems to have appeared 3.8 billion years ago. By 3.5 billion years ago, we have fossilized stromalites which are IDENTICAL to the ones still made today by prokayote blue-green algae in the Indian ocean.\n\nThe first eukaryote organisms (with cells structures like ours) first show up 1 billion years ago. Within 500 millions years from then, complex forms can be found in the fossil record which are ancestral to modern lineages. But here are NO fish, amphibians, reptiles, mammals or birds. These all arise later in sequence by evolutionary modification as the fossil record clearly shows.\n\nThe bottom line is that only evolution provides a comprehensive argument that explains what we see in the fossil record. The Intelligent Design people are frauds who misrepresent the data and are no more credible that the Gish/Morris combine of liars that plaugued us in the 70s and 80s.\n\nI (Dr. Art Sippo) am a 53 year old cradle Catholic with a BS in Chemistry (Magna cum laude)from St. Peter's College, an MD from Vanderbilt University, and a Masters in Public Health from Johns Hopkins. After Catholic apologetics, paleontology is my favorite hobby. I have been studying it since I was a kid in the 1950s.\n\nWith regard to "macroevolution" that term is actually passe. It is still touted by Creationoids so that they can say they support microevolution but not macroevolution. These terms were used around 30 years ago before the discovery of the complexity of eukaryote genetics. Microevolution was what happened when there were single alterations either in DNA sequences or protein sequences due to mutations. There were other mechanisms that worked in bacteria (eg., conjugation, plasmids) but their utility in eukaryotes was questionable. At that time it was assumed that prokaryote (eg, bacterial) genetics was directly applicable to eukaryotes (eg, mammals). We now know that this is not so.\n\nEukaryote genetics is so complicated that it has not been fully elucidated. There is modification of the transcription of DNA to messenger RNA, a further cropping of m-RNA into introns and extrons, and further modification of the proteins for which they code. None of this happens in prokaryotes.\n\nAlso eukaryotes use a "homeo box" generalized assembly kit which is functionally identical in all lineages and which can with slight tweaks make large changes in how the genotype (DNA data) is expressed into a phenotype (external structure). \n\nAlso, eukaryotes use chromosomes which rearrange themselves spontaneously in several different ways. This helps to contribute to evolution in the absence of any DNA mutations.\n\nAll of these mechanisms -- and more -- contribute to evolution. In fact everything that is necessary for what had been called "macroevolution" is present in these more complex genetic systems.\n\nWith regard to the changes in species of higher animals, many Creationoids have said that there were large systematic gaps between major taxa. They are right, In the linnean system there are large SYSTEMatic gaps, but these gaps are due to the system of classification, and do not correspond to real biological differences. Linnaeus was a Creationoid. He thought that each species was distinctly made by God. So he created a complex classification system that emphasized distinctions and did not assume common descent. In reality, his classifications were merely man-made conventions that limped badly. For example, the Class Reptilia included not only lizards but snakes (some of which bear live young and don't lay eggs), turtles, crocodiles (that all have 4 chambered hearts), dinosaurs (some of which have feathers), ichthyosaurs, mososaurs, plesiosaurs, and pterosaurs (some of which have fur). The problem with fish is even more complex.\n\nIn many cases, an organism does not fit into the Li
568942
Based on fossil, genetic, and molecular evidence, we have a long train of ancestors in our history.  Modern humans and other primates, such as monkeys, have a common ancestor that lived about 25 million years ago, and our ancestor would probably *not* be considered a "monkey."  Before that were early mammals, and before that mammal-like reptiles, the sauropsids. Before that were early reptiles, and amphibians.  And yes, before that, about 440 million years ago, one of our ancestors was a fish.  So you are correct.