Category: Invertebrates
This phylum of animals inhabits marine waters worldwide. They are named for their distinctive rows of cilia, or combs, that they use swimming – they are actually the largest organism in the world that uses cilia for locomotion. They possess a decentralized nerve net rather than a brain and display a wide range of body forms –for example, coastal species have sturdy bodies that are able to withstand constant buffeting by waves while some open-ocean species are so fragile it is difficult to collect them for study.
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
