A Random Walk
To the Zoo——
Think about the last time you visited a zoo. You undoubtedly enjoyed seeing the elephants and watching the monkeys. You may have walked through the reptile house and looked at the alligators and tortoises. Perhaps you saw some endangered species such as the panda or tiger. Your zoo may even had a "bug house," where various kinds of invertebrates are seen. The zoo was probably located in a parklike setting, with all sorts of trees, bushes, and grasses. Yet for all the diversity of like the zoo, representatives only a tiny fraction of the living things on our planet.
How could such an incredible array of living things developed on a once lifeless planet? How could living things on our planet include such extraordinary variety, from a slime mold to a sperm whale? The answers to these questions requires us to think not only about what life is, but how it became to be this way.
