The pelagic species position themselves in water in a slightly oblique position. If their side bristles detect movement, a quick sweep of their tail allows them to swiftly dart off in the direction of prey. They are able to swim across short distances very quickly. Their ability to swim is probably dependent on their body muscles, but the precise manner of how it is done is still not known. The fins are thin, transparent structures supported by fin rays and do not contain muscle fiber. Fins enlarge body width and enhance the buoyancy of the animal. In some species the fins contain gelatinous material. Fins do not play an active role in swimming.
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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.