* Also known as amphioxus
* Small, fish-like marine animals
* Filter feeders
* Lack a backbone or vertebrae
* Have a notochord, which is a flexible rod-like structure that supports the body
* Have a simple nervous system
* Have a simple circulatory system
* Have a simple digestive system
* Have a simple excretory system
* Have a simple reproductive system
Small fish
* Vertebrates
* Have a backbone or vertebrae
* Have a more complex nervous system
* Have a more complex circulatory system
* Have a more complex digestive system
* Have a more complex excretory system
* Have a more complex reproductive system
* Can be freshwater or saltwater fish
* Can be found in a variety of habitats, including rivers, lakes, ponds, oceans, and estuaries