Question: How do you classify invertabrae?

Invertebrates are all animals that do not have a vertebral column, so they don’t have a backbone or spine, like insects, snails, crabs, prawns and octopus (to name a few). The name vertebrate and invertebrate are not used as scientific names anymore, they are just a common name to generally split animals with and without a backbone.

The actual scientific ranking and splitting of animals groups is much more complicated then that. Because some animals have tricked us, like the sea squirt (Ascidiacea). In the adult there is no backbone or spinal cord, but in the larvae stage there is!! The larvae of a sea squirt looks like a little fish, it has a simple backbone called a Notochord. When the larvae lands on a rock to settle it changes into an adult, and the notochord is reduced to a very simple nervous system.

Search for sea squirt on Google to see some photographs.