From the Ted Talk by Judy Cebra-Thomas: How turtle shells evolved... twice
Unscramble the Blue Letters
At first, turtle embryos look very simailr to those of other reptiles, bidrs, and mammals, except for a bugle of cells called the carapacial rdige. The ridge expands around the body between the neck and lower back, creating a disc shape. It guides the formation of the upper part of the turtle’s shell, cllaed the carapace, likely by anacttritg the cells that will become ribs. Instead of curving downwards to make a regular rib cage, the ribs move outwards towards the ccrpaaaail ridge. They then secrete a signaling protein that covrtnes surrounding cells into bone-forming cells. These fifty bones grow until they meet and connect with sutures. A ring of bone solidifies the carapace’s edges. The outer layer of skin cells produces the scaels, known as scutes, that cover the carapace.
Open Cloze
At first, turtle embryos look very _______ to those of other reptiles, _____, and mammals, except for a _____ of cells called the carapacial _____. The ridge expands around the body between the neck and lower back, creating a disc shape. It guides the formation of the upper part of the turtle’s shell, ______ the carapace, likely by __________ the cells that will become ribs. Instead of curving downwards to make a regular rib cage, the ribs move outwards towards the __________ ridge. They then secrete a signaling protein that ________ surrounding cells into bone-forming cells. These fifty bones grow until they meet and connect with sutures. A ring of bone solidifies the carapace’s edges. The outer layer of skin cells produces the ______, known as scutes, that cover the carapace.
Solution
converts
called
attracting
carapacial
scales
similar
ridge
bulge
birds
Original Text
At first, turtle embryos look very similar to those of other reptiles, birds, and mammals, except for a bulge of cells called the carapacial ridge. The ridge expands around the body between the neck and lower back, creating a disc shape. It guides the formation of the upper part of the turtle’s shell, called the carapace, likely by attracting the cells that will become ribs. Instead of curving downwards to make a regular rib cage, the ribs move outwards towards the carapacial ridge. They then secrete a signaling protein that converts surrounding cells into bone-forming cells. These fifty bones grow until they meet and connect with sutures. A ring of bone solidifies the carapace’s edges. The outer layer of skin cells produces the scales, known as scutes, that cover the carapace.