Evolutionary History of Animal Groups

Evolutionary History of Animal Groups - Evolutionary...

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Evolutionary History of Animal Groups Coelomates are animals that have internal body cavities, or coeloms . Humans are coelomates, since we have an abdomenal cavity containing digestive organs, some of the excretory and reproductive organs, and a thoracic cavity that contains the heart and lungs. Coelomates also form a variety of internal and external skeletons. External skeletons and coeloms appeared during the Cambrian-Ordovician time. These skeletons offered several advantages to their producers: 1. Secretion of a mineral shell that allowed the animal to use the shell as a mineral repository. 2. Protection from drying out in the intertidal zone during low tides. 3. Protection from predators. 4. Sites for anchoring muscle attachments, offering new patterns of locomotion and increased strength. Deuterostomes and Protostomes Protostomes (mollusks, annelids, and arthropods) develop so that the first opening in the embryo is the mouth (protostome = first mouth). Protostomes are bilaterally
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Evolutionary History of Animal Groups - Evolutionary...

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