Why re-invent the wheel when you can copy from millions of years of evolution? Okay, so there aren't that many animals that use the wheel for locomotion, but there are plenty of other tricks that biology has figured out. By studying how insects fly, we could improve the designs of future flying robots, and there are some biological materials like spider webs and pearls that we still haven't been able to replicate exactly. Here are just a few other examples of how we're learning from biology.
If you'd like to read more awesome and interesting stuff, check out this unrelated (but not entirely random!) Techdirt post