Why are Sharks are immune to cancer ?
967267
similar to roaches which also cant get cancer, they're bodies are made of a different type of cell. Sharks are composed mainly of cartilage tissue, which is hard for cancer to thrive in. Thus, they're chances of getting cancer are very small. They can still get cancer in internal organs, but not in their extremities.
573717
cancer is an auto-immune disease and can be reversed with\nproper cell to cell communication or glycosylation. the \nimmune system kills off cancerous cells. all you need are \nglyconutrients. send me and email for more info.
517749
Humans are not it's main source of food.  Therefore the shark would only attack a person if 1. was incited by a feeding frenzy 2. shark has not been able to get normal source of food for some time 3. the shark is confused by the shape, and takes an investigative bite.  A shark can easily kill a person, but usually after the initial bite they usually let go.  Very rarely are people actually killed and consumed by the shark.
675249
Elasmobranchs (sharks, skates, and rays) indeed have an interesting sensory physiology enabling them to sense a variety of physical stimuli.  But fear is not one of them. That said, it is true though that fear may be associated with either the release of particular chemical compounds, but far more importantly and likey in regards to your question, with particular behavior.  And in that sharks are not very different from any other predator.\n\nThe sense of smell is indeed very well established in almost all elasmobranchs; if you ever take a look at a shark's brain note the extremely large bulbi olfactorii, the areas of the brain where smell is first analyzed.  The sentivity of shark noses for blood is often emphasized, but you must not imagine sharks to be "swimming noses."  Rather, they rely on different senses for different environmental conditions, prey, etc. The priority assigned to either one of the possible sensory modes is largely dependent on the life-style of the animal.  Given that there are over 400 different species, there are a few variations.\n\nLike many other aquatic animals (e.g., teleosts, but also amphibians) sharks rely on their lateral line organ for detecting objects in greater distances.  The lateral line organ is a tiny canal running along the side of the animal underneath the skin.  it is open to the environment through a set of pores, through which the shark can sense pressure differences in the water, as they are being produced for example by a fish in distress.  This can of course be misunderstood as "smelling fear," when in fact it is more like "sensing the panicked movements of a potential prey."\n\nThe electromagnetic sense of elasmobranchs is perhaps most amazing from a human point of view, since it is so very different from anything we have.  All elasmobranchs have Ampullae of Lorentzi, with which the animals can indeed sense bioelectric fields.  These organs are so sensitive that a dogfish can sense the bioelectric field induced by the beating heart of a flounder covered by sand.  Sharks also use this organ for a magnetic compass.  By swimming through the earth's magnetic field, a shark will induce an electric current that will either run from its back to its belly (when the animal swims in an eastern direction), or from its belly to its back (in western direction).  with its own electromagnetic sensores, the animal can sense the induced electric current and its direction and can thus orient itself along the magnetic field of the earth.  Again, very sexy and very helpful, but no detector of fear!\n\nNow, some sharks use their eyes when they hunt prey, and this may an important point in regards to your question.  Great white sharks (Carcharodon carcharias) often attack their prey (e.g., seals) from far below, orienting themselves visually in their attack and going for the tell-tale silhoutte of the pinniped.  Some sharks, like the lemon shark (Negaprion brevirostris), have an interesting eye, where the sensitivity of the retina changes from light of one particular wavelength during day time to one of a different wavelength during night time.  This Purkinje-shift allows the animals to see optimally during day and night.  Now, many animals (or humans) in distress show a particular behavior.  Sometimes, a flight response is what is initiated when faced with a predator.  This behavior can signal the shark that the fleeing animal (or human) is afraid and therefore not a danger but rather a potential prey.  Consequently, fear in humans that cause a flight response may cause sharks to respond accordingly.  This may also be misunderstood as "smelling fear."  This, by the way, is the same kind of behavior a cougar, dog, or bear will dislay.\n\nThat said, there is always the possibility that during fear a human may release certain chemical compounds that the shark can smell.  But I doubt that this is something really significant in a real-life encounter.\n\n
781893
These bacteria probably have the lux gene which codes for bioluminesence. A resonable mechanism that would cause this to arise is mutation. These lighted cells would probably have benefited some how from glowing in the dark. Some deep sea fishes have bacteria which code for this gene (Vibrio fischer) Which may have helped these fish find food in the dark waters. Thus those fishes without this gene would have died out because of natural selection. What you could do is put these fishes with the bacteria that glow in the dark in the same pool of dark water as the fishes without this gene. Then provide a limited food source so that not everyone could receive food and only the strongest would survive. If the fishes without this bacteria eventually died out but the others stayed alive, you have proven your hypothesis. If not, then failure willl be an obsticle to overcome.\n\nHope i was helpful
616561
The scales- Same structure, shape, and composition- In fact, a related function, since sharks will brush the sides of their body by interesting possible food items to scrape off a little (of your skin, for example) in order to "taste" it with special sensors in the skin.  Generally, if a shark does this with a human, they will *not* attack further.
491000
No, all sorts of animals will kill sharks including jellyfish, eagles, dolphins, snakes, crocodiles and countless predatory fish such as barracuda.\n\nThere isn't very much special about sharks, they are just another fish. In the ocean any fish will be eaten by most fish that are bigger then it. Sharks are no exception. If a barracuda or marlin is bigger then a shark then it will eat the shark. If an eagle can catch a shark near the surface it will do so.\n\nSharks are eaten as much as any other fish in the ocean, and by just as many predators.\n\nAnd giant squid wouldn't eat very large sharks. Despite their large size they live mostly on prey animals much smaller than themselves. Any shark much bigger than a dogfish would probably be safe from a squid.
487932
wow, people who have no clue try to sound like medical experts.  I'm no medical expert, but I can lead you to a better answer.\n\nTelomere immortalization is one known element of cancer, so I'll use that to explain why smoking is a leading cause of cancer, but just know there are several other things that happen besides this.\n\nBasically cancers are cells that grow, bond, and refuse to die.  We're talking about cells that try to become immortal, and you can understand why.  The carbons and chemicals in your lungs actively block oxygen, which your lungs were designed to need.  Every time your body replaces dead cells (which it does constantly), it checks the environment they're in to see if they need to make adjustments.  Oxygen is essential to cell survival, so if you're choking them to death, they'll get desperate.  Some will just die.  Some will go on gasping for air.  But some will rebel from the body, which is killing them, and find their own mission.  And a tumor is born.  These are like lawless vigilantes who don't give a damn about being part of the body anymore.
1132436
Things like radiation and chemotherapy kill the 'wild' cells that cause and spread cancer, but nothing has been created yet to permenantly destroy those cells so they don't come back.
112066
Sharks in general are poikilotherms or ectotherms (their body temperature is similar to the temperature of the surrounding water). \nHowever, some species (high-power fast swimmers belonging to family Lamnidae, such as genus Alopias -thresher sharks- and Lamna - porbeagle and others- ) have partial endothermy. That is, they're able to "hoard" the heat generated by muscle activity and therefore achieve differential temperature zones in their bodies, which are some degrees above water temperature. This is achieved by means of special countercurrent blood vessels and rete mirabilia. \nSome typical body parts that are kept warmer are the brain and eyes, the swimming muscles, and the "core" with the visceral organs, which is logical given that higher temperature allows a higher metabolic rate of these important organs.\n\n---------------------\nAmy: not only sharks, also tuna and related bony fishes are endotherms. And some reptiles too.\n------------------\nNew update: Wow, this question keeps getting answers that state that only  birds and mammals are endotherms. Please, people, if this is what they taught you at school, try to investigate a little further. Of course MOST sharks are "cold-blooded" (that is not the happiest term, it's better to say ectotherm - meaning that it gets its body heat from outside - or poikilotherm - meaning that body temperature is variable). But endothermy is an advantageous trait, and it has evolved independently in many animal groups.
178433
The above is not complete. Don't have time to go into details, but check out this website:\n\nhttp://www.learner.org/channel/courses/biology/textbook/cancer/index.html\n\nI suggest reading the entire chapter if you don't have time for that, I suggest the section on Tumor Biology and the treatment section
78044
Yes, in theory cancer has existed since the beginning of life. It exists in almost all known species (in one form or another). Cancer, simply put, is when a cell loses its ability to regulate division, and begins dividing (reproducing) uncontrollably. This happens most often due to a genetic mutation in the DNA/RNA of the cell. Mutations can be caused by radiation (including UV rays), toxins in the environment, and many other mutagens.\n\nIt occurs more often in older people because they have usually been exposed to more of these mutagens throughout their lives than younger people. There is also a genetic component – if you inherited genes from your parents that were precursors to cancer, then it takes fewer mutations before getting a cancer cell.\n\nThis is also the most likely explanation for why there are so many different types of cancer today -- people live MUCH longer than they did even 50 years ago, and are therefore exposed to more cancer-causing mutagens in their lifetime. People are also (on average) having children much later in life, which makes it more likely to pass on genes that have more genetic mutations.
891823
It was once believed that all sharks had to swim constantly in order to breathe and could not sleep for more than a few minutes at a time. Oxygen-rich water flows through the gills during movement allowing the shark to breathe. While some species of sharks do need to swim constantly, this is not true for all sharks. Some sharks such as the nurse shark have spiracles that force water across their gills allowing for stationary rest. Sharks do not sleep like humans do, but instead have active and restful periods.\nhttp://www.flmnh.ufl.edu/fish/sharks/nsrc/Basics.htm#sleep\n\nIt is unclear how sharks sleep. Some sharks can lie on the bottom while actively pumping water over their gills, but their eyes remain open and actively follow divers. The spiny dogfish's spinal cord, rather than its brain, coordinates swimming, so it is possible for a spiny dogfish to continue to swim while sleeping. It is also possible that a shark can sleep with only parts of its brain in a manner similar to dolphins.\nhttp://en.wikipedia.org/wiki/Sharks#Shark_sleep\n\nIt depends what you mean by sleep. When humans sleep we are not conscious of what is going on around us, we kind of shut-down for a while and are not able to walk around unless we happen to be sleep-walking. Sharks rest in a different way. They can rest part of their brain while still swimming along, semi-aware of what's around them. Sharks that are able to stop swimming will settle on the seabed, and species like the British Bullhuss shark actually close their eyes - so they appear to sleep like we do. In our aquarium I have seen two Sandtiger sharks bump into each other nose-to-nose. They were so startled, they both took off at great speed in opposite directions. This suggested to me that they were dozing on the move and not paying full attention to where they were going, but I have never seen them bump into the sides of the tank when snoozing, so they normally seem to have an idea of where they are. A lot of research has been done on sleep in humans, and many mysteries still surround sleep and its importance to healthy living, but conducting similar research on sharks is almost impossible for practical reasons, we have a lot to learn about sleep and its purpose in fish and other animals.\nhttp://www.national-aquarium.co.uk/databases/FAQsLibrary/index.asp?FAQCategoryID=&FAQID=767&Sear
1042893
The ones that actually adhere to the sharks are remoras. They're fishes belonging to order Perciformes, family Echeneidae, and they have a dorsal sucking disk with which they attach to sharks , but also to other bony fishes, turtles or marine mammals. These fish clean their "host" and feed on their leftovers.\nThis is what a remora looks like:\nhttp://www.amonline.net.au/fishes/fishfacts/images/enaucsh2.jpg\n\nThe other, more typical-looking fish with dark and light vertical stripes, are pilotfish. These also belong to order Perciformes, but to a different family, the Carangidae. Their scientific name is Naucrates ductor. They were called "pilotfish" because of the belief that they "guided" sharks. Actually, they're semi-obligate commensals of sharks, rays, other bony fishes and turtles, which means that they depend very much on them to feed on their leftovers.\nThis is what a pilotfish looks like:\nhttp://www.horta.uac.pt/imagdop/Servicos/Naucrates_ductor/035_s410_31.jpg
544448
WebMD is a good website.  However, it is NOT true that only doctors can have an informed opinion on this.  I am a research biologist who studies cancer in my laboratory.  So, I think my opinion is valid even though I am not a Medical Doctor.  Please see my answer on your previous question for a more thorough explanation of the causes of cancer.\n\nRadiation is known to induce mutations, which can then result in cancer.  However, it is NOT clear whether the radiation dosage from power lines or cell phones is sufficient to cause cancer.  I suspect it is NOT or else we would be experiencing a cancer epidemic in America.
854620
no, sharks are NO invertebrates, they got a spine
520975
That's an interesting question!\nThe short answer would be "Different evolutionary paths", which is true. But those paths imply adaptive and functional differences. \nThe teeth of sharks are not too different from those of other tetrapods. Aside from birds, most tetrapods have many generations of teeth (this is called polyphyodonty), and those teeth are usually not strongly attached to the jaws. They`re more or less easily lost and replaced during normal activities. So, why don't we mammals have such a useful feature? \nThe loss of all those teeth replacements was a tradeoff for our acquisition of better tooth occlusion. Occlusion is the way the surfaces of the upper and lower teeth contact each other, and in mammals, our chewing teeth (molars and premolars) have complex occlusal surfaces, which allow for slicing food (shearing like scissors), crushing food (cusps and basins that act like a mortar and pestle), and other ways of basically, disintegrating food items. \nThe thing is, the precise interlocking of cusps and vales is not easy to achieve (as anybody with occlusion problems has probably heard from the dentist). So the hypothesis is that the evolutionary path of mammals "focused" on one generation of perfectly occluding teeth. Thus, molars erupt late in life, grow slowly, and are not replaced. And the other teeth (incisors, canines and premolars) have a first, "milk" teeth generation that allows the young mammal to feed while its skull is expanding. Then, by the time its growth has slowed down, the definitive teeth erupt and take their places (they would not fit in the small jaws).\nThe teeth of man, as those of all primates, are brachydont. This means that they don't keep growing once they've erupted completely. However, the enamel that forms the outer cover of the teeth is the hardest substance in our bodies, and is able to endure the wear from our food. However, many other mammals that eat more abrasive foods (plants, and especially grasses) have permanently growing teeth (hypsodonty). This is, in a way, the equivalent of having multiple generations of teeth; their teeth keep growing throughout part of their lives (as in the case of horses) or all of their lives (like many rodents and ruminants). But we cannot "recover" the capacity for multiple teeth generations that we "gave up" evolutionarily when we became mammals.