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Across 1. People were freaked out by the relatively small number of genes. It's down to something like _________ protein-coding genes in a human genome. 5. Tiktaalik had the bone structure that is seen in the arms and legs of every ______ limned animal. 7. One percent might not sound like much, but it's still some ____________ of DNA's chemical letters. 8. In total he has found some 21 different mutations responsible for microcephaly. Sometimes, one of the DNA chemical letters is _________. 10. _______ ________ genes determine where the head goes; where the limbs go, and what form they take: whether they are arms, legs, or wings. 11. Scientists now realize that not all genes are created equal. Some make the stuff of our bodies, and ___________ are needed to turn many of these stuff genes on and off. 14. Tiktaalik is a perfect __________ form.Much of it's body is that of a fish, covered in scales, however had an arm-like fin. 15. However in humans we are different compared to chimps in __________ letters, a massive mutation. 17. The ______ molecule is one of the real secrets of life. It's a perfect system for storing the vast amounts of information that's necessary for building all kinds of creatures. 19. So a _______ change, a couple of DNA letters, could have a profound effect. 20. These variations accumulate and eventually new species branch off. This is evolution by __________ __________. It is one of the keys to how new species are formed. 21. Sometimes, one of the DNA chemical letters is replaced with another letter, sometimes letters are ____________ entirely. 25. Mutation generates ___________, differences between individuals. 26. Charles was offered a place on the British Navy ship, the H.M.S._________. 32. Oftentimes, the origin of whole new structures in evolution don't involve the origin of new _________ or whole new genetic recipes. 33. Hox genes have been found in all complex animals, from the velvet worm that dates back some 600 million years ago, to the modern human. In that time, the letters of their DNA have remained virtually ___________. 34. Basically, you can make __________ changes just changing switches. 35. Ultimately one type of __________ could be transformed into something utterly different. 36. It all goes back to Darwin's idea of the tree of life, that all life-forms are ultimately _________.

Down 1. When she looked at that DNA in chimps and compared it to the same DNA in a chicken, it was different in just ____ letters. 2. This was a revelation. The same genes were responsible for the beaks in all types of finch. Any differences were in _________ and _________. 3. On the Galapagos, the _____________ had diversified into many kinds, with different shells depending on which island they lived on. 4. _________ is a critical ingredient in the recipe for evolution. Without mutation, everything would stay constant, generation after generation. 6. If Darwin were right, somewhere out there, there had to be a transitional form, a fossil that was part ________, but had the beginning of legs. 9. Darwin realized that __________ must be the starting point for change in nature. 12. These genes determine where the ________ and ________ of the animals going to be, the top, the bottom; the left, the right; etc. 13. Given all the obvious differences between humans and chimps, you might expect our DNA to be really different. But, in fact, it's more like _________ percent identical. 16. But one of port of call on Darwin's voyage proved more important than all the others: the ______________. This cluster of 13 isolated islands lies 600 miles off the coast of Ecuador, in the Pacific Ocean. 17. It's not the genes you have but how you use them that creates ___________ in the animal kingdom. 18. In the wild, a tiny _________ might make the difference between life and death. 19. Darwin had this amazingly bold idea: the tree of life - that all ________ were connected 22. The gene in humans was radically different from that of a chimps. There had been a large series of ___________. 23. The _____ genes are what throw these switches, which tell the stuff genes what to do and when. 24. If Darwin were right, somewhere out there, there had to be a transitional form, a fossil that was part fish, but had the beginning of ________. 27. From the earliest common ancestor, over billions of years, they have _________ and diversified, so that creatures that started out looking the same, evolved to become completely different. 28. Switches are not _________. They don't make stuff like hair, cartilage or muscle, but they turn on and off the genes that do. 29. Eventually, hunting through the vast stretch of DNA that does not code for proteins, he found it, a section of DNA that ________ in the lake stickleback. These mutations meant that the switch was broken. 30. The pattern that Darwin saw was that the creatures that survived were those best __________ to the specific environments they lived in. 31. Originally, there must have been just one type of ___________ on the Galapagos, it had diversified into many kinds with different beak shapes. 32. Amazingly, in all four limned animals, even humans, exactly the same __________ create the long, upper arm bone.