How do we classify invertebrates? SCIENCE CH. 1 L. 3 NOTES PG. 18 21 Vocabulary Invertebrates animals with no backbone Invertebrate Facts Most animals in the world are invertebrates Some are too small to be seen Largest can easily stretch the length of a basketball court (giant squid) Mollusks Soft body without bones Some have shells for protection Some have gills Some absorb oxygen through the skin EExamples: SSnails SSlugs CClams SSquid Worms Belong to many different phyla Can be very large or very small Can range in size from microscopic to over 23 feet long Examples Flat worms Flat and thin Live in wet, damp places Roundworms Live in water or on land Segmented worms Example: Earthworm Arthropods Largest phylum of animals Arthropod means jointed feet Bodies are divided into separate segments Dichotomous Key Used to identify unknown organisms Is used by answering a series of questions A key can be made up for any group of organisms that is being observed Birds, insects, trees, etc