Amphibians

Amphibians: Transport, Excretion, Respiration regulation, Nutrition, Reproduction development

__The Circulatory System__ The circulatory system of a Frog forms a double loop. The first loop carries oxygen poor blood from the heart to the lungs and skin, and takes the oxygen-rich blood from the lungs and the skin back to the heart. The second loop takes oxygen-rich blood from the heart and sends it to the rest of the amphibian's body and the carries oxygen-poor blood from the body back to the heart. An amphibian's heart has three chambers. These three chambers are the left atrium, right atrium, and the ventricle. Oxygen-poor blood circulates from the body into the right atrium. Oxygen-rich blood from the lungs and skin enter the left atrium. When the atria contract the left and right atrium empty their blood into the third chamber, the ventricle. Next the ventricle contracts and pumps the blood into one large blood vessel, which divides into smaller blood vessels in the amphibian's body. Most oxygen-poor blood goes to the lungs while most oxygen-rich blood goes to the rest of the body, but some of the blood mixes together.
 * Look on pg. 785 in our biology book for more information and a picture**

__The Excretory System__ Like all vertebrates amphibains have an excretory system. The kidney's of an amphibian filter waste out of the blood. The Urine travels tubes which are called ureters. From the ureters the urine travels into the cloaca. Next the urine can be passed outside the body or the urine may be stored temporarily in a urinary bladder just above the cloaca.
 * Look on pg. 785 in our biology book for more information and a picture**

__Respiration__ In the younger amphibians gas exchange occurs through the skin and and the gills. In an older amphibian gills are usually replaced by lungs, but some gas exchange still occurs through the skin and the lining of the mouth cavity. In amphibains such as frogs and toads lungs are developed quite well but in other terrestrial salamands there are no lungs at all. This kind of amphibain exchanges gases through the skin and the mouth cavity.

__Reproduction__ When a frog reproduces, the male climbs onto the back of hte female and squeezes. When this occurs the female frog releases as many as 200 eggs. The male frog can the fertilize the eggs. The eggs of a frog do not have a shell and usually try out if they are not kept moist. Because of this the eggs attach to underwater plants using a transparent jelly that incases the eggs. This also makes it harder for predators to reach the eggs. When the frog eggs hatch into larvae they are called tadpoles.[|Frog eggs]
 * Look on pg. 786 in our biology book for more information and a picture**

__Nutrition__ A young amphibian such as a tadpole eats constantly. Tadpoles are usually filter feeders or herbivores. Tadpoles mainly eat algae. Adult frogs develop an apparatus and a digestive tract. Adult forgs are meat-eating amphibians. Almost all adult amphibians are carnivorous. The legless amphibians can only open and close their jaws to catch their prey. Frogs and Salamanders also have long, sticky tongues, which they use to capture their prey.