Since the adoption of the Bill of Rights â the first 10 amendments to the Constitution, ratified in 1791 â only 17 amendments have cleared the hurdles necessary to be codified in the nation's founding document, the last of which was ratified in 1992.
Other examples are leeches and sand worms. Believe it or not, 75% of the entire animal kingdom is right here in phylum Arthropoda! Arthropods include all insects, spiders and crustaceans so it is a HUGE phylum. Arthropods are known for having protective exoskeletons and segmented legs. Some have 6 legs, 8 legs or even 10 legs but none of them have a backbone.
The Animal Kingdom (Clade 1) is a natural, highly diverse group of organisms, most of which are multicellular and develop from a blastula (Margulis and Schwartz 1998). However, I depart from Margulis and Schwartz (1998) in that I include the choanoflagellates and the myxozoans as part of the natural group.hey are diploblastic, that is, they have two cells layers (endoderm and ectoderm) in mature animals. Endoderm is the layer that lines the gut while the ectoderm is the cellular layer on the outside of the animal.