Why did animal phyla appear so suddenly during the Cambrian explosion? Several v
ID: 168902 • Letter: W
Question
Why did animal phyla appear so suddenly during the Cambrian explosion? Several variables have been hypothesized to play a role in the sudden appearance of diverse animals during the Cambrian explosion. Forexample, the "higher oxygen levels" hypothesis invokes an environmental trigger and the "evolution of predation" hypothesis invokes ecological interactions. Erik Sperling, Andrew Knoll, and colleagues set out to test the hypothesis that these two hypotheses are linked. Could the oxygen atmosphere enable the evolution of predation? Part A Sperling and Knols approach was to compare the number of predatory polychaete worms (pronounced pol-ee-KEET, um Annelida) living today in different gen environments. They chose polychaetes as a model system because these worms have diverse feeding strategies and live in diverse marine environments, yet all have the same basic body plan. Using the figure as your guide, describe the body plan of a polychaete worm. ANNALLA Chordata Segmentation (vertebraes,Explanation / Answer
The Polychaete body plan :
1.Segmented tube within a tube. This refers to the fact that their outer body is like a tubeand there is an inner tube.
2."Coelom" This is the area between the two tubes. Polychaetes have a Coelom.
3.Polychaetes are Triploblastic.This is a condition in which there are three primary germ layers.
4. Polychaetes are Cephalised. In some Polychaetes the first three segments are Cephalised, in others the first segment is cephalised. This means that the nervous tissue and sense organs begin to group at one end. A precurser to the head.
The symmetry is bilateral and Polychaetes have a chain nervous system and closed vascular system.
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