section_path: Diversity/Numbers and habitats of major phyla
section_name: Numbers and habitats of major phyla
paragraph_text: Numbers and habitats of major phyla
  
  The following table lists estimated numbers of described extant species for the major animal phyla, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. Using patterns within the taxonomic hierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011.