Diversity of Major Groups

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Diversity of Major Groups

The diversity, or variety, of animal species in the major groups is staggering. Scientists currently recognize more than one million species of animals, and this number does not include all species of bacteria, archae, and protozoa. Invertebrates make up 95 percent of the more than one million known species. Arthropodsspiders, horseshoe crabs, crustaceans, insects, centipedes, millipedes, and scorpionsare the most successful phylum in the animal kingdom. Arthropods account for 80 percent of all known species of animals. Insects are the most successful arthropods. Scientists estimate that there are one billion insects for each human on Earth!

see also Biological Evolution; Phylogenetic Relationship of Major Groups.

Allan B. Cobb


Barnes-Svarney, Patricia. The New York Public Library Science Desk Reference. New York: Macmillan USA, 1995.

Ruppert, Edward R., and Robert D. Barnes. Invertebrate Zoology. Fort Worth, TX: Saunders College Pub., 1994.