BIO 2135 Study Guide - Final Guide: Water Vascular System, Metabolic Waste, Nephridium
1 Dec 2014
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Document Summary
Osmoregulation and excretion are closely related processes in animals and where an animal lives often affects how it can carry out these processes. Example platyhelminthes they are parasites in another host"s digestive system. They have a good enough surface to volume ratio to simply use simple diffusion. Because they live in a moist environment (either in freshwater or in a host digestive tract), their metabolic waste is ammonia: terrestrial protostome. They use metanephridia to filter out their metabolic wastes (contains both ammonia and urea: marine deuterostome. The metabolic waste is filtered through simple diffusion through the dermal branchia and the tube feet of the water vascular system. Because they are in a marine environment, they don"t have much of an excretory system and can simply use passive diffusion. All animals have to obtain oxygen and transport it to actively metabolizing tissues that require it. The starfish does not have a circulatory system.
