Presenter notes: Open by asking the class to name ten animals, and write them on the board as they come. Almost every list will be cows, dogs, tigers, birds, snakes, fish. Then count how many have a backbone. Usually all ten. Then tell them that out of every hundred kinds of animal on earth, about ninety seven have no backbone at all. Their list is drawn entirely from the rarest three. That gap between what we notice and what is actually out there is a good place to begin.