What makes up an individual species?

Search: species

Why: In Breakfast of Champions, p. 87:

...there were too many species on the planet already, and new ones were coming into being almost every hour.

Answer: Oh - I think I learned this in 7th grade: "A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring." But! "While in many cases this definition is adequate, more precise or differing measures are often used, such as based on similarity of DNA or morphology."

• The "species problem" addresses the difficulty in defining the word in a way that applies to all naturally occurring organisms
• Most textbooks follow Ernst Mayr's definition of a species: "groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups"
• However, this excludes animals mated in captivity, animals whose offspring are normally sterile, and animals which may be physically and physiologically capable of mating but do not normally do so in the wild

Source: Wikipedia

The More You Know: Total number of species (estimated):

7 - 100 millions (identified and unidentified), including:

• 5-10 million bacteria
• 74,000-120,000 fungi

Of the identified eukaryote species we have:

• 1.6 million, including:
  • 297,326 plants, including:
    • 15,000 mosses
    • 13,025 ferns and horsetails
    • 980 gymnosperms
    • 258,650 angiosperms
    • 9,671 Red and green algae
  • 28,849 fungi & other non-animals, including:
    • 10,000 lichens
    • 16,000 mushrooms
    • 2,849 brown algae
  • 1,250,000 animals, including:
    • 1,203,375 invertebrates, including:
      • 950,000 insects
      • 81,000 mollusks
      • 40,000 crustaceans
      • 2,175 corals
    • 59,811 vertebrates:
      • 29,300 fish
      • 6,199 amphibians
      • 8,240 reptiles
      • 9,956 birds
      • 5,416 mammals