nerve ring mouth gonopore gonad axial gland ampullae esophagus siphon intestine test radial canal ring canal Polian vesicle Aristotle's lantern pharynx radial nerve peristomial membrane nerve ring mouth
Sea urchin and sand dollar anatomy. (Illustration by Emily Damstra) Grzimek's Animal Life Encyclopedia
Sand dollars burrow into the sediment by moving at an angle to the surface, and heart urchins burrow by excavating allowing the animal to sink vertically into the sediment. Forward movement is then achieved by using its powerful laterally orientated spines.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.