There may be as many as 30 million species of animals, plants, and other organisms on Earth.

The total number of animal species currently known is about 1.9 million. Click on each of the numbers below for a look at a member of some animal groups.

• More than 1,000,000 (click) of those species are arthropods — insects, crustaceans, arachnids, and their kin.

• About 70,000 more are molluscs — snails, clams, squids, octopi, and their kin.

• Another 20,000 or so are flatworms, and about 25,000 are roundworms.

• Just over 4,600 mammal species are known today.

But animals are only a small part of the picture.