Evolution and systematics

The Nematomorpha consists of two clades: the class Nec-tonematoida and the class Gordiida. The nectonematids are parasites of marine crustaceans such as crabs and shrimp. The gordiids are usually parasites of terrestrial arthropods such as crickets, grasshoppers, beetles, mantids, and cockroaches. Based on molecular evidence, the phylum Nematomorpha has been shown to be the sister group to nematodes. The phylum contains two orders, two families, and two genera—all corresponding to the two clades. Overall, the phylum contains approximately 230 species.

Fossil gordiids have been found emerging from a cockroach trapped in fossilized amber dated at 15-45 million years ago. However, it has been suggested that this group might date back to the Carboniferous.

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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