BIOL 2030 Chapter Notes -Water Vascular System, Symmetry In Biology, Tube Feet
10 Jan 2014
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Lab 7 - phylum arthropoda ii and echimodermata. Most oxygen enters the starfish via diffusion into the tube feet (with the water vascular system). The tube feet latch on to surfaces and move in a wave, with one body section attaching to the surfaces as another releases. Similarities - both molluscs and echinoderms possess circulatory systems that are predominantly open, symmetrical bodies (radially symmetrical in echinoderms, bilaterally symmetrical in molluscs), nervous systems, and digestive systems. Differences - although echinoderms possess a complete digestive tube (tubular gut), it is very simple, often simply leading directly from mouth to anus. It can generally be divided into a throat, stomach, intestine and rectum. They also possess an open and reduced circulatory system consisting of a central ring and five radial vessels, but no heart. Secondary radial/bilateral symmetry - they are bilaterally symmetrical during larval development but become radially symmetrical as adults. Echinoderms are secondarily radially symmetric whose ancestors were bilaterally symmetric.
