What role does extinction play in macroevolution?
449031
remember food chain!!\n\nwhen one species ceases to live their food starts too overpopulate creating dangerous unbalance in chainfood.\nLike in australia, long time ago they released rabbits into the wild. They didn't have many predators to hunt rabbits down and keep them from overpopulating, thats why they had rabbit hunting seasons, they were overpopulated.\n\nplus, if one species increases in number that means more food is needed, that means the food source will get depleted faster and if that food source is shared with some other species they will cease to exist as well.\n\nVote best if it answers your question!
171371
Should natural disaster occurs, natural selection occurs, as the species that adaptable enough to survive the natural disaster will continue their existance and those which not adaptable enough to survive these will be wiped out from the area.\nThose which able to continue their existance will inherit the traits that enable them to survive the natural disaster and of course, those who cannot survive will not have a chance to inherit their traits. \nThose will results to the increase of the "resistance" of the surviving species to the same natural disaster.
199584
"Macro-evolution" is a theory inasmuch as evolutionary events that have purportedly occured over millions of years and resulted in the appearance of new species can not be experimentally reproduced or observed. In contrast, "Micro-evolution," which describes genetic change within a particular species, has been observed and can be witnessed over and over again. \n\nThe mechanics of micro-evolution are most evident in lower order organisms such as bacteria, viruses, insects, etc. Just think about cockroaches and how quickly, in a matter of a few generations they can adapt to certain pesticides and become immune to them. \n\nThe reason why macro-evolution has been readily accepted as fact when it really isn't is because the principles of micro-evolution have been extrapolated to the illogical conclusion that species can go through so many minor genetic changes that they eventually become entirely new species. This has not been proven and unless you are able to live millions of years or be able to maintain documentation that lasts that long, macro-evolution can NEVER be proven.
1156179
"Diversity of Species" is one way nature protects itself from complete extinction.  In a complex environment, there are multiple paths to survival.  So species have evolved that suit each of these paths.  It only makes sense that species that are not a threat to one another would coexist in such a place.  It also makes senses that predators and prey would reach a natural balance (ie it only works if there are more gazelles than lions).  If a disease comes through that wipes out the gazelles, then the lions will all starve.  But life will go on because there are sloths and toads and ants and ballywoates (okay, I made that up) and fish and insects and so on....\n\nhope that helps.\n\nI'm just gald there's apparently a young person out there who still believes there is a diversity of species!
818209
a. Predators reduce the number of prey, simply because they eat them! But in the long run, evolution allows the prey to compensate by reproducing at a more frequent rate. This is why foxes reproduce much more slowly than do rabbits. Rabbits get eaten a lot by other animals such as foxes, so their survival as a species depends on their numbers.\n\nb. Predators evolve to become more efficient hunters. Over time, they grow sharp teeth, acute senses, speed and stealth.. Prey evolve to be better able to run away or hide from predators. They may become more alert of their senses, develop faster legs, learn to climb trees.. etc.\n\nHope that helps!
461824
Extinct species, if not extinct by human activity (shooting them, cutting their forests down, etc.), have extinct for a reason - they did not fit well to the enviournment.\nRecreation of such species may destabilize the delicate balance of nature.\nMoreover, any human interferance with nature, whether trying to do good or bad, can only harm it.\n\nThere are two (1.5) reasons. I think you can start with these, and probably the rest will come to mind after writing this. If not, I believe that other people will have further ideas.\n\nGood luck!
391779
It doesn't work like that.  \n\nWe're going to have to back up a long ways so you can understand first how evolution works, then I can answer your question.\n\nOkay.  The dinosaurs didn't "turn into" birds.  Most of them died out due to massive climate changes that took millions of years.  Some smaller dinosaur species gradually, again over millions of years, evolved into avians.  \n\nOther reptiles are still around today, but in forms that can effetively compete with mammals, all of which started from a small rodent-like creature that coexisted with the dinosaurs.  After the dinos died out, this mammal evolved into the millions of mammalian species we see today, again over a period of perhaps 200 million years.\n\nSome of these mammals evolved into primates; some of these primates evolved into hominids, and some hominids evolved into homo sapiens.  The rest died out because they could not effectively compete against existing species.  "Survival of the Fittest" and all that.  Many primate species survived to evolve into the thousands of different kinds of primates we see today.\n\nIt's actually quite elegant, when you see the pattern clearly.
653816
Evolution is a theory.
724158
Er... the theory of evoltion?  It's just a theory though.  Lots of loop holes.  :)
1327
There is this really great book called EXTINCTION by the Ehrlichs(?)...which starts out with a beautiful analogy about the environment. It starts off with this guy who removes rivets (screws) from an airplane wing so that he could sell them for profit. Each rivet/screw represents a unique species that plays an important role in our ecosystem. The loss of each one has an adverse effect on the whole structure. It is true that such effects may or may not have an immediate recognizable effect on us but that does not mean that it is not happening. Also, we humans, have proven that we are really self centered that we do not recognize the damage that we are doing unless it hits us in the face. There are countless examples of chain reactions in the ecosystem due to a loss of an integral species. For example, (although I am no longer certain about the details) due to the misuse of a pesticide by farmers in rural Peru, an outbreak of more resistant  pests evolved. The farmers in reaction started to use more pesticides which affected the other species that naturally feed on and control these pests. The situation got so bad that it escalated to such an extent that cats which controlled the rat population died out because they got the higher dose of the poisonous pesticide in their system. Finally, (believe it or not) they had to fly cats to the area and dropped them from helicopters...thus it did rain cats that day in Peru.
996277
Extinction is applied only after a species hasn't been recorded for a specified period of time (commonly 50 years) and only after an adequate search has been carried out. It has a very specific meaning. Essentially when a species is declared extinct it means that there is very good reason to believe it is extinct.\n\nPresumed extinct is used fairly regularly. It means that there is reasonable grounds to assume extinction, but either the requiredtime period hasn;t elapsed or for one reason or another exhaustive searches can't be carried out.  Presumed extinct is usually applied either to species that were never well known, so it's impossible to know where to focus a search, or to species that inhabited rugged regions or war zones so that thorough searches are impossible.
609697
Here's one theory:\n\nClimate Model Links Warm Temperatures to Greatest Extinction\nWork supports theory that rise in levels of carbon dioxide triggered die-off\n\n\n\nScientists at the National Center for Atmospheric Research in Colorado have created a computer simulation showing Earth's climate in unprecedented detail at the time of the greatest mass extinction in history.\n\nAccording to an August 24 press release from the U.S. National Science Foundation (NSF), the work supports a theory that an abrupt and dramatic rise in atmospheric levels of carbon dioxide triggered the massive die-off at the end of the Permian Era, 251 million years ago.\n\nDuring that time, an estimated 90 percent to 95 percent of marine species and 70 percent of land species became extinct -- an extinction even greater than that of the dinosaurs, 65 million years ago.\n\nMany scientists equate high concentrations of carbon dioxide with warmer temperatures, and a close correspondence has been found between carbon dioxide and temperature for the past 570 million years.\n\nAt the end of the Permian, Earth had a single landmass (a supercontinent) called Pangea. Higher-latitude temperatures were 10-30 degrees Celsius warmer than today, and volcanic activity had released large amounts of carbon dioxide and sulfur dioxide into the atmosphere over a period of 700,000 years.\n\n"The implication of our study is that elevated [carbon dioxide] is sufficient to lead to inhospitable conditions for marine life and excessively high temperatures over land would contribute to the demise of terrestrial life," the authors concluded.\n\nTo understand how such conditions might have affected climate and life around the globe, the researchers used the Community Climate System Model (CCSM), which can integrate changes in atmospheric temperatures with ocean temperatures and currents.\n\nThe CCSM indicated that ocean temperatures warmed significantly at higher latitudes because of rising atmospheric levels of carbon dioxide, a greenhouse gas.\n\nIn the ocean, warmer temperatures reached a depth of about 4,000 meters, interfering with the normal circulation process in which colder surface water descends, taking oxygen and nutrients deep into the ocean.\n\nAs a result, ocean waters had little oxygen, proving deadly to marine life. Because marine organisms no longer removed carbon dioxide from the atmosphere, the rate of warming accelerated.
12704
Glenn, I appologize if this comes off pretentious, but I would like to address part of your question. Unfortunately, it's not the part you probably want answered, but I feel it's the most important part of your question.\n\nWhen it comes to biology/evolution, to ask the question "why" is unanswerable. It's not the way things work when it comes to evolution. Things are the way the are now because of millions of years of selective pressures dictated all current living things into their current constructions.\n\nIn fact, the question "why" is nearly impossible to even consider when it comes to biology. Things are the way they are not for any particular reason. Maybe there were organisms that had developed a large "blowhole" like structure that was at the end of their nasal cavity. But for whatever reason, which may or may not had anything to do with the having two small nares or a bigger blowhole, environmental pressures allowed one organism to succeed and pass along their traits (including the nairs) and the other became extinct.\n\nWe can talk about structure's function that it provides, but that structure was in no way "designed" that way to provide that function. In fact that function may or may not have been essential to that organism surviving and passing along that trait. Some traits are simply along for the ride. In those cases it's other structures that provide increased fitness which allows certain organisms to outcompete and prosper through evolutionary time. \n\nIn the case of having two nares at the opening of the nasal cavity, I have no idea if this was a critical structure for the propogation of organisms on earth. I can make the guess, however, based on the fact that many animals do have similar structures, that this feature was present early on in evolutionary time. The fact that this trait has been maintained suggests one of two possibilites: either these stuctures do have some level of importance for organisms' fitness or 2) there is no real pressure otherwise that has forced a change from this trait that developed early on.\n\nIf there have been some insight gained which is true, I'm not aware. Hopefully someone who has that expertise will find your question and answer. In the meantime, I hope you will consider why the word "why" is not an appropriate place to start the path to finding out.
209928
i havent heard that example, but its possible. that would possibly fall into the category of microevolution...like when birds beaks get bigger or smaller to crack different nuts. its still a bird, with slightly different attributes. that would be an example of artificial rather than natural selection though, since it would be people choosing what they think is attractive, rather than nature killing off people who were less well equipped to deal with the environment.
1178059
It certainly doesn't support the evolution theory. Having more than two nipples is merely an erroneous repetition of already existing information in the DNA.\n\nFor macro-evolution to take place, it would require the creation of new information altogether.\n\nThat never happens.\n\nhttp://www.needGod.com
566098
i think it might of been the start of the extinction and possibly other factors as well.   through out time animals adapt so it is possible that the meteor hit along with the rapid climate change caused this all the happen or appear to happen at once.   how do we know that the extinction was not already in progress before the meteor hit.   i don't think we will ever know.   Science is fact and a little bit of art when they come up with these ideas.
477598
Perhaps... the weather during the early part of the Cretaceous was warmer than today (and more uniform.)  I'm actually in the process of writing a paper exploring the possibility of hadrosaur hibernation in northern Alaska.\n\nI took a tour of a dinosaur resource center today.  The tour guide said that ability to adapt is what saved KT survivors.  Crocodiles can go months without eating.  Birds migrate.  Fish could swim to deeper water.\n\nIt is still highly debated to what caused the Cretaceous Tertiary extinction.