What part of the tube foot creates suction to open clams whenever the starfish feeds?
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they are called suckers on the ends of the tube feet.  they are controlled by the water-vascular system in echinoderms, such as starfish.  \n\ngood luck with the dissection!  i did it a few weeks ago...make sure to check out the two stomachs!!
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They are plant-like protists with two flagella to move. The move in a corkscrew like manner
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Around the cell. It's what holds all the squishy bits in (cytoplasm etc.)
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spiral valve (shaped like a spiral staircase) fills the cylindrical intestines and allows absorption of the food in a short span of intestine.\nA spiral valve is the lower portion of the intestine of some sharks, rays and skates. A modification of the ileum, the spiral valve is internally twisted or coiled to increase the surface area of the intestine, to increase nutrient absorption\n\nThe intestine of a shark, in comparison to that of mammals, is much shorter. Sharks have compensated for this problem by having a spiral valve, or a scroll valve, inside the intestine to increase the absorptive surface of the intestine.
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You know how when you suck on a straw you get your drink to move up through the straw? This happens because by sucking, you are creating a partial vacuum on one side of the straw, and the atmospheric pressure on the liquid on the other side, now having nothing to counter it, pushes the liquid up through the straw. But no matter how much you suck, you cannot reduce the pressure on your side of the straw to less than zero (i.e. a complete vacuum), and as such there is a maximum height to which you can raise a column of water - that height depends solely on the atmospheric pressure on the other side of the straw. This means that you can construct a barometer simply by having a glass tube immersed vertically in some liquid, and pumping out all the air on one side of the tube, and then sealing the tube - the height of the liquid then gives you the ambient air pressure. Water, however, is not very dense, and so your barometer would have to be very large if it used water. To get around this problem, scientists use Mercury, which is a much denser liquid, to measure the pressure. A pressure of 1 mm Hg is simply a pressure that can support a column of Mercury 1 mm high under this arrangement.
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Agree with the above. Additional points - the fertilized egg, or zygote, begins to divide, just as in other animal species, still floating freely in the water.  It eventually develops into a ciliated, free-swimming larva called a veliger. The larva swims about in the water, many of them being eaten by small predators like copepods, and filter-feeding organisms. Eventually, those larvae which survive begin to develop the organs of a mature clam, including a mantle, the shell-producing organ.  The mantle then begins to extract minerals, especially calcium, from the ocean water and starts to form the shell.  The weight of the tiny shell carries the young clam to the bottom, where it continues to grow, if it lands on suitable substrate.  However, if the species is a rock-dweller, like marine mussels, and lands on a muddy or sandy bottom, it dies.  Likewise if the larva of a sand-dwelling clam lands on a hard rock bottom, it dies.
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ROACH, JELLY FISH, STAR FISH, CLAM, OYSTERS, FLYS, SPIDERS
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If you've strolled along a beach in Maine, you've probably found a sand dollar. But what is a sand dollar? Children have been known to say that sand dollars are pressed sand that has been dried or even the money of mermaids washed-up from the deep. In reality, the fragile disk is the skeleton or "test" of a marine animal. By the time the test washes up on the beach it is missing its velvety covering of minute spines and appears somewhat bleached from the sun. It is hard to believe it was once alive. \n\nSand dollars are from the class of marine animals known as Echinoids, spiny skinned creatures. Their relations include the sea lily, the sea cucumber, the star fish and the sea urchin. When alive, the local species, Echinarachnius parma is outfitted in a maroon-colored suit of moveable spines that encompass the entire shell. Like its close relative the sea urchin, the sand dollar has five sets of pores arranged petal pattern. The pores are used to move sea water into its internal water-vascular system which allows for movement. \n\nSand dollars live beyond mean low water on top of or just beneath the surface of sandy or muddy areas. The spines on the somewhat flattened underside of the animal allow it to burrow or to slowly creep through the sand. Fine, hair-like cilia cover the tiny spines. These cilia, in combination with a mucous coating, move food to the mouth opening which is in the center of the star shaped grooves on the underside of the animal. Its food consists of plankters and organic particles that end up in the sandy bottom. \n\nDue to their diminutive edible parts and relatively hard skeleton, few animals bother sand dollars. One animal found to enjoy them on occasion is the thick-lipped, eel-like ocean pout. \n\nOn the ocean bottom, sand dollars are frequently found together. This is due in part to their preference of soft bottom areas as well as convenience for reproduction. The sexes are separate and gametes are released into the water column as in most echinoids. The free-swimming larvae metamorphose through several stages before the test begins to form and they become bottom dwellers. \n\nSince the sand dollar lives in sandy locations, anyone who would like to collect their shells should comb beaches as the tide recedes. The very best time for collecting is after a heavy storm, as many of the shells that have died are dredged up by the increased wave action.\n\nCheryl Page \n\nInformation for this article was taken from: \n\nGosner, Kenneth L., Guide to Identification of Marine and Estuarine Invertebrates; 1971 by John Wiley & Sons, Inc. \nRobbins, Sarah Fraser and Clarice Yentsch, The Sea Is All About Us ; 1973 Harcourt Brace Jovanovich, Inc.
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Some of them are buoyant and sleep floating on the surface breathing air. Others can do what in humans is comparable to the "dead man's float" where you are under the water motionless then tilt your head back only, rise to the surface to breathe, tilt it back and resubmerge. Hippos can do this without ever waking up so I assume some marine mammals can too.
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There is such good contact, between fine hairs on the feet of certain animals and the surfaces to which they cling, that van der Waal's forces can hold them firmly. Yet these forces are weak enough to let the animal peel its feet off, to walk or jump etc.\n\nSee for example these articles:\n\nhttp://www.abc.net.au/science/news/enviro/EnviroRepublish_1094975.htm\n\n"Spiderman suit should have been hairy\nJulian Cox\nABC Science Online"\n\nand\n\nhttp://www.abc.net.au/science/news/stories/s138473.htm\n\n"Gecko's sticking powers revealed\nFriday, 9 June 2000 \n\nScientists have, for the first time, identified the mechanism allowing geckos to defy gravity and are using the discovery to develop a new type of adhesive.\n\nIn this week's issue of Nature, University of California, Berkeley, biologist Robert Full and colleagues, report that a gecko's foot is covered by almost 500,000 hairs, each ending in spatula shaped structures that collectively create a molecular interaction with the surface....."\n\nMore at those pages.\n\n:-)\n\nPS: G'day from Australia\n\n:-)
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Do you mean closed around the spatula? The speculum is what holds the vaginal canal open. The spatula is what the doc uses to scrape the cervix. I've never heard of it happening, but I think it is possible. The cervix has an opening and it is a muscle, so if something entered the opening, it could cause a muscle spasm making the cervical opening close down on the object. But like I said, I have never heard of this happening and I worked as a nurse in a multi-physician office for about 10 years, but it is physically possible.
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Cuttlefish don't have any air-holes on the inner surface of their tentacles.  Or anywhere else for that matter.\n\nCuttlefish are strictly marine, and don't really have much interaction with air at all.  They breathe water, live in water, breed in water and feed in water.\n\nPerhaps you are refering to the suction cups on the tentacles?  The inner surface of the tentacles has a number of suction cups used in grabbing prey or other items.  The number of suction cups varies depending on the species of cuttlefish, and their age/size, and probably individual variations as well.  \n\nSo the answer would be somewhere between some and lots.
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Unlike marine mammals such as whales and dolphins with lungs that store oxygen from the surface air, fishes have gills. Gills are a series of membranes located on each side of the fish that function as respiratory organs. As water passes over this system of extremely fine gill membranes, the fishes absorb the oxygen from the water. The gills contain a network of fine blood vessels (capillaries) that take up the oxygen and diffuse it through the membranes. When fishes are taken out of water, they suffocate, because their gills collapse and they are unable to absorb oxygen.In many ways, the interior of the fish resembles that of many other animals. The digestive, circulatory, and nervous systems are very similar to those of other vertebrates. However, what really makes a fish different from other animals is its respiratory system. \n\n\n\nA fish’s respiratory system is determined primarily by the fact that it spends its entire life in water. Unlike the marine mammals such as whales, a fish has evolved in such a way as to not require frequent trips to the surface to breathe air. Fish have developed gills, on which they rely for the oxygen necessary for a fish’s limited metabolism. \n\nMany animals have gills at some stage of their life (even humans have them at an early stage of their development in the womb), but fish retained these gills and they are still a functional part of their anatomy. Fish use their gills to extract oxygen from their watery environment. The process starts with the fish’s mouth, which is how the fish takes in water. When a fish opens and closes its mouth, it is actually pumping water back through the gills and is thus breathing. Most fish have an effective pumping system that involves the mouth and the outer cover of the gills, called the operculum. When the fish’s mouth opens, the operculum closes, drawing water into the fish’s mouth. When the fish closes its mouth, the operculum opens, allowing fresh water to cross the gills. Other fish have a less effective pumping system, requiring them to swim constantly to keep fresh, oxygenated water flowing over the gills. These types of fish, such as tuna, generally swim with their mouths partly open. Incidentally, while many fish have nostrils, the nostrils are used only for a sense of smell, and play no part in respiration. \n\nOnce through the mouth, the water continues past structures called gill rakers. The gill rakers are essentially a filter system for the gills, straining the water to sift out floating food particles or foreign material. After passing through the gill rakers, the water continues through the gill arches and actually passes over the gills, which are suspended between the mouth cavity and the operculum. Each gill is made of two rows of gill filaments, which are extremely thin membranes sticking out into the water flow. Each of the gill filaments is composed of rows upon rows of lamellae, which are thin, disc-like membranes loaded with a capillary network. The water flows across the lamellae, and oxygen and carbon dioxide are exchanged directly across the capillary membrane. The capillaries are situated to take best advantage of the water flow; fish can actually extract up to 85% of available oxygen out of the water. Since water contains only 2-5% of the available oxygen that air at sea level does, such a high efficiency is extremely important. \n\nFrom the gills, the deoxygenated water passes out the operculum, and the oxygenated blood joins the circulatory system. Despite the efficiency, some fish require more oxygen than others. This helps to explain why some fish thrive in specific habitats. For example, trout prefer northern streams because the cool water of the streams tends to retain dissolved oxygen, and the active trout need the extra oxygen. Carp, on the other hand, are sluggish and do not need as much oxygen, which is why carp can thrive in warm, relatively stagnant ponds, such as ornamental ponds. Goldfish, unlike most f
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1."If the cell is disturbed, one can observe the discharge of the outer coating of trichocysts. These spine-like structures, analogous to nematocysts (the stinging cells of jellyfish), can fire out from the cell in a fraction of a second at the slightest physical or chemical stimulus. Discharged trichocysts may remain attached at their base; until they detach, the cell resembles a disheveled porcupine. The exact function of trichocysts is not known but it is thought they may be used for capturing prey"\n\n1."Upon mechanical or chemical stimulation, these trichocysts can be discharged (as shown on the model) to produce long, sticky protein threads that remain attached to the organism.  It is believed that these structures can be used for defense."\n\n\n2."The paramecium moves by swimming. For the paramecium to move forward the cilia beat on an angle, backward. This means that the paramecium moves by spiralling through the water on an invisible axis. For the paramecium to move backward, the cilia simply beat forward on an angle. If the paramecium should run into a solid object the cilia change direction and beat forward, causing the paramecium to go backward. The paramecium turns slightly and goes forward again. If it runs into the solid object again it will repeat this process until it can get past the object. "
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Panaque fish have spoon-shaped teeth which they use to rasp at submerged wood. Bacteria in their guts convert plant cellulose into nutritious chemicals.
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An extention of the cell membrane which has the ability to move providing propulsion to the prokaryote
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http://en.wikipedia.org/wiki/Starfish\nDiagrams and descriptions on this page.