What is an Invertebrate?

Invertebrates are animals without a backbone, comprising over 30 phyla with diverse characteristics. They range from those with hard exoskeletons to soft-bodied species relying on water for support. Arthropods, including insects and crustaceans, are the largest phylum. Mollusks, such as slugs, snails, squid, and octopuses, have a mantle, sometimes forming a shell. Sponges, the simplest invertebrates, lack organs and systems, using water flow for sustenance. The term 'invertebrates' is a convenient way to refer to all species without a backbone.

How do sponges obtain food and remove waste?

Why is the term 'invertebrates' considered a convenient classification?