(Sea squirts)

Phylum Chordata Class Ascidiacea Number of families 24

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Benthic, solitary, and colonial species whose adults are sessile, almost exclusively fixed, firmly attached, or lying free on the sea floor; they usually filter feed; larvae are free swimming

Photo: These tunicates (Phallusia julinea) have a larval stage with notochord, forerunner of the vertebrate spine. (Photo by ┬ęDavid Hall/Photo Researchers, Inc. Reproduced by permission.)

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Essentials of Human Physiology

Essentials of Human Physiology

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.

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