The features used to classify animals: levels of organisation, symmetry, germ layers, the body cavity, segmentation and the notochord, and how they sort the phyla.
3 lessons, about 1 h 15 min3 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabAnimals are classified by a few basic features. Sponges work at the cellular level, coelenterates at the tissue level, flatworms at the organ level and higher animals at the organ system level. A gut may have one opening or two, and blood may flow in open spaces or in vessels. Bodies are asymmetrical, radial or bilateral.
Diploblastic animals, the coelenterates, have an outer ectoderm and an inner endoderm, with a jelly called mesoglea between. Triploblastic animals add a mesoderm. A body cavity lined by mesoderm is a coelom. Roundworms have a pseudocoelom, with mesoderm only in scattered pouches, and flatworms have no body cavity.
In metameric segmentation, as in the earthworm, the body is divided into segments with some organs repeated in each. The notochord is a rod formed from mesoderm along the back of the embryo; chordates have it and non-chordates do not. Together with the earlier features, these sort the animals in a key to the phyla.
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