Category: Invertebrates
Ticks are small, blood-sucking arachnids of the order Parasitiformes, with over 900 known species. They most likely emerged during the Cretatious (65-145 million years ago), and have thrived in warm, humid climates, ever since. Parasites, ticks survive by drinking the blood of their hosts -- typically mammals or birds, occasionally reptiles or amphibians -- an act that in and of itself is typically not harmful, but one that makes them a serious vector for diseases that affect humans and other animals, such as Lyme disease.
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
