Evolution and systematics

The class Appendicularia is made up of one order, three families, and 64 species. Appendicularians are related to ben-thic tunicates and are commonly called larvaceans because they retain the larval tadpole stage as sexually mature adults. These animals are transparent and lack the outside covering, or tunic, of their benthic relatives. The body is composed of a trunk containing most of the internal organs and of a tail with a notochord running down the middle. The trunk secretes a mucous house, which may enclose the animal, as in Oikopleura and Bathochordaeus species, or enclose only the tail, as in Fritillaria species. The body and house appear jelly-like and are therefore grouped as gelatinous zooplankton. Larvaceans are small, ranging from a 0.04 in (1-mm) body length with a 0.2 in (4 mm) house to Oikopleura to 1 in (25 mm) body length with a house more than 6.6 ft (2 m) in diameter for the giant larvacean Bathochordaeus.

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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