invertebrates are classified into how many groups?
The Invertebrates unit explores six groups of invertebrates— poriferans (sponges), cnidarians (such as sea jellies and corals), echinoderms (such as sea urchins and sea stars), mollusks (such as octopuses, snails, and clams), annelids (worms), and arthropods (such as insects, spiders, and lobsters).