Describe Class Agnatha in details?
Class Agnatha takes its name from the Greek word "gnathos," which means jaw, and "a," which is the prefix for "without." These jawless fishes date back 470 million years ago, and are thought to have been the first vertebrate animals to evolve. The extant groups, or groups that are still living, include the lampreys and the hagfish.
Their bodies are long and cylindrical in shape, much like an eel's. Lampreys migrate to the sea from freshwater habitats, while hagfish are exclusively marine. Lampreys are parasitic. They use suckers on their mouths to attach themselves to other fish and then rasp the flesh with their tongues in order to suck the host's blood. Hagfish, on the other hand, are scavenger feeders, as their mouths are unlike those of lampreys. Most people would not find these organisms, as a group, particularly attractive.