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 number of known species for all animals other than arthropods is about 250,000. The largest group within the phyla of arthropods and the most diverse class in all kingdoms, is insects.