Category: Invertebrates
This very large group of arthropods includes familiar animals such as shrimp, crabs, lobsters, crayfish, and barnacles. Like other arthropods, they have an exoskeleton which they must molt in order to grow. Crustaceans are distinct in their possession of two-parted (biramous) limbs and unique larval form. They are an important source of food for humans, with over 10 million tons being produced via farming and fishing every year. Most crustaceans are aquatic, though a few are adapted to a terrestrial lifestyle.
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
