Category: Invertebrates
This diverse phylum is made up of an estimated 1 million species of roundworms, many of which are parasitic. Nematodes have adapted to almost every possible habitat on earth, including marine and freshwater habitats, soils, tropical to desert to polar climates, and from very low to very high elevations. They are quite literally everywhere, and they outnumber us and all other animals in species count and actual numbers by a long shot! Species of these slender worms can vary greatly in size, from microscopic proportions to over a meter in length! Widely known roundworms include hookworms, pinworms, whipworms, and the species that causes trichinosis.
The world’s first Animals
Invertebrates were the first animals to evolve. While their soft bodies left precious few records behind, there are fossils of sponge-like animals that are 665 million years old, as well as traces of tracks and burros from worm-like animals going back 1 billion years. By comparison, the earliest birds appeared only 150 million years ago! And not only were invertebrates first, they are the most plentiful of animals - it is estimated that 97% of all animals living on the Earth today are invertebrates, with several groups containing more species than all vertebrates combined!
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Discover Animals is a web-based educational resource offered by the NAIA
