how does the spiral valve within the shark intestine aid in efficient digestion of food by sharks.?
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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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In a few sea urchins, the spines are tipped with venom sacs.If a predator attacks the urchin, it may rupture the venom sac at the same time the skin of the predator is punctured. Venom is then introduced directly into the wound along with a portion of the spine that continues to lacerate the tissue.\n\nThere is one more elaboration of spines seen in sea urchins, and that is the development of structures called "pedicellariae." Pedicellariae are constructed of several small spines which have become modified to articulate with one another and function as snapping jaws. Each pedicelliaria is typically found on an elongate and extensible stalk, and they reach out to pinch any small animals or body parts, such as the adhesive tube feet of a predatory sea star, that threaten the sea urchin.\n\nSome urchins, particularly the blue tuxedo urchins, Mespilia globulus, use some of their tube feet to attach and hold shells, small rocks or debris to their surface. These attachments are thought to be "tactile" camouflage; basically a way to hide the urchin from predators that lack eyes, such as sea stars. If a sea star encounters the rocks on the surface of a small sea urchin, it may not perceive of the urchin as prey sufficiently rapidly enough, allowing the urchin to escape its grasp. For further information, you can browse from this website...
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Easy. Sharks belong within the subphylum Vertebrata.
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It digests food. The stomach doesn't do as much digesting as the small intestine.
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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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The digestive tract is complete and ciliated, with a mouth, anus and complex stomach. The pattern of the stomach varies according to the mollusks diet.  Food is taken up by cells lining the digestive glands arising from the stomach, and then is passed into the blood.  Undigested materials are compressed and packaged, then discharged through the anus into the mantle cavity and are carried away from the animals in the water currents.  This packaging of wastes in solid form prevents fouling of the water passing over the gills. \n        Excretory functions are carried out by a pair of nephridia, tubular structures that collect fluids from the coelom and exchange salts and other substances with body tissues as the fluid passes along the tubules for excretion. The nephridia empty into the mantle cavity.
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The spiral of a screw. Its also the lines segmenting a worm.\n*fyi: earthworms have 5 hearts*
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Chemical digestion is accomplished using enzymes - chemicals that break down the structure of whatever food the amoeba is eating.  Mechanical digestion comes from movement - like chewing - using physical force to break apart the food, but not alter the food's chemical structure (that is what the enzymes do - alter the chemical structure)
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When you chew you start the digestive process; then you swallow and the food goes into your stomach where it is mixed with gastric juices which help breakdown your food before it goes into the digestive track of the bowels.  Your stomach/bowels are constantly contracting and moving things along. Godloveya.
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Sea urchin belongs to a group of animals called: echinodermata (among them: starfish, brittle star and sea cucumbers). All echinoderms have a water-vascular system, a set of water-filled canals branching from a ring canal that encircles the gut. The canals lead to podia, or tube feet, which are sucker-like appendages that the echinoderm can use to move, grip the substrate, or manipulate objects. These tube feet are extended and retracted by hydraulic pressure in the water-vascular system. Pedicellaria are small, snapper-like skeletal elements that are used by the echinoderm to keep small organisms from settling on its body.
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Invertebrates, the starfish can turn its stomach inside out. It will the surround its prey and digest the food.  When the food is digested the stomach will return to its normal position.\n\nNasty eh?
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That's a great question!\n\nMy first thought was No, but I googled and found a great piece on worm hearts (see link below).\n\nIt turns out they have something that does a similar job, but is not a heart like we mammals have. Follow the link below for all the details.
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1.Hydrolyzes proteins via pepsin (a protease). \n2.Kills pathogens by dousing them with hydrochloric acid. 3.Stores food during digestion. \n4.Mechanically digests foods a little bit by churning the acid chyme.
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I just saw on the Discovery Channel that they have created a shark repellant.  This is a device that omits a frequency that the shark dislikes.  A scubba diver attached this to his tank and then the swimmer pushed a button that released the frequency...I guess sharks do most stuff because of vibrations and frequency in the water...it's kinda like their eyes.\n\nAnyways, scientists are hoping to develope this further so they can get rid of nets along the coast <which kill sharks, dolphins, and turtles>.
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The spiral shell allows the animal inside to grow.  As it grows, the sheel develops a wider turn at the open end and the animal grows into this space.
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That depends on the size of the shark and its scales. Shark scales are actually denticles embedded in the skin, with their point directed posteriorly. The morphology of these denticles is particular to each shark species, and in most cases, these denticles keep getting bigger as the animal grows (these skin denticles are shed and replaced just like sharks' teeth). \nSo, if you happen to rub with your naked skin against the shark, in the direction opposite that of the orientation of the denticle tips, you could get seriously grazed and chafed. \nAlthough many aboriginal cultures in different parts of the world have used shark teeth as knives, I've never heard of their skin used in this way. But the dry skin of some dogfish sharks was indeed commercialized as sandpaper, before the advent of artificial versions.
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The gastrointestinal tract or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and expels the remaining waste.\n\nThe GI tract differs substantially from animal to animal. For instance, some animals have multi-chambered stomachs.