How do bones heal themselves?

How much do wildfires contribute to carbon release? How do bones heal themselves? Why do weeds seem to grow faster than other plants? Why do some animals float, but others sink? Why do ducks like spinach? How did we evolve different blood types? Why do some people's temperature go down when they're feeling ill? How many of our metals come from space? Why do snails come out in the rain? Dr Chris Smith and Clarence Ford have all the answers...