Geologic History: A History of Life on Earth

a happy face spiderSpecies

As you learned earlier, new types of organisms are often discovered. Even in modern times, scientists continue to explore and find new samples of Earth’s rich diversity of living things. Imagine that you discover one of the presently unknown organisms on Earth. What would you name this spider if you were the one who discovered it?  Its name is the Hawaiian happy face spider. Can you see why? Happy face spiders come in a variety of colors besides yellow, including black, red, green, orange, and brown. Also, each individual spider has a slightly different "smile." Aside from these differences, all the happy face spiders have the following in common:

  • same body shape, mouthparts, number of legs, etc.
  • interact in the same way with their environment and with other organisms
  • the same reproductive behavior
  • same hunting and eating behavior
  • can mate with each other and produce more happy face spider offspring

Click on the tabs below to read about diversity.

Image of organisms in a coral reef.

The organisms in the coral reef show species diversity. You see several different species, including a type of fish, starfish, and coral.


Regardless of any other differences, all happy face spiders are the same species because of what they have common. Each individual organism has variable traits, but as a whole, they still represent just one species. A species is a group of organisms with similar (but not always identical) appearance and behavior, and that can interbreed or mate to produce fertile offspring. From microscopic bacteria to complex land animals, the diversity between species on Earth is called species diversity. Examples of species include humans, horses, oak trees, goldfish, daffodils, killer whales, and the list goes on and on.
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Image of kittens with their mother.

The cats show genetic diversity. They are all the same species but have individual differences.


The Hawaiian happy face spiders help point out a key point of this section. Many species on Earth show tremendous diversity of traits among its individual organisms. We see this in humans (different body sizes, skin color, hair color, etc.), in puppies from the same litter, and from just about every other living thing. This variability within a species is called genetic diversity.

Species diversity describes the variation among different species and genetic diversity describes the variations among different individuals of the same species.

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