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LOCOMOTION - GAS EXCHANGE - DIGESTOIN

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by

aron campbell

on 9 April 2010

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Transcript of LOCOMOTION - GAS EXCHANGE - DIGESTOIN

Fish swim by exerting force against the surrounding water. There are exceptions, but this is normally achieved by the fish contracting muscles on either side of its body in order to generate waves of flexion that travel the length of the body from nose to tail. FISH LOCOMOTION Most fish generate thrust using lateral movements of their body and caudal fin. But there are also a huge number of species that move mainly using their median and paired fins. GAS EXCHANGE Gas exchange is more difficult for fish than for mammals because the concentration of dissolved oxygen in water is less than 1%. Fish have developed specialized gas-exchange organs called gills, which are composed of thousands of filaments. The filaments in turn are covered in feathery lamellae which are only a few cells thick and contain blood capillaries. This structure gives a large surface area and a short distance for gas exchange. Water flows over the filaments and lamellae, and oxygen can diffuse down its concentration gradient the short distance between water and blood. Carbon dioxide diffuses the opposite way down its concentration gradient. The gills are covered by muscular flaps called opercula on the side of a fish's head. DIGESTIVE SYSTEM The digestive system of fish is quite simple when compared to that of the humans. Of course there are many variations between species. A fish's mouthparts are modified for unique food habits. Some species such as sawhorses that feed on small zooplankton or other tiny food sources have tubular sucking mouthparts. In this case, it would be incapable of eating larger foods. In contrast, some predators capture & swallow prey larger than would seem possible, but special joints enable them to open their mouths to enormous proportions while their esophagus expands to allow prey to be swallowed whole, in this aspect the digestion system of a fish if very dependent on the type of fish and what the fish eats. Fish ingest food through the mouth and break it down in the esophagus. In the stomach, food is further digested and, in many fish, processed in finger-shaped pouches called pyloric caeca, which secrete digestive enzymes and absorb nutrients. Organs such as the liver and pancreas add enzymes and various chemicals as the food moves through the digestive tract. The intestine completes the process of digestion and nutrient absorption. anal fin - the fin on the lower side of the body near the tail
caudal fin - the tail fin

dorsal fin - the fin on the upper side of the body

eye - sight organs located on the head

gills - fleshy organs that are used for breathing - they are located on the side of the head
lateral line - a series of sensory pores (small openings) that are located along the sides of fish - they sense vibrations in the water
mouth - the part of the body which the fish uses to catch food - it is located at the front of the body

pectoral fin - each of the paired fins on either side of the body, near the head

pelvic fin - each of the paired fins on the lower side of the body, near the head
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