AP BIOLOGY Student Exploration: Embryo Development Gizmo 2022

Activity A (continued from previous page) 4. Observe: Switch to stage 13. What do all of the embryos have in common at this stage? The tail bud begins to form as well as the somites and brachial arches. In mammals, brachial arches develop into structures in the head and neck. In fish and frogs they become part of the jaw and structures that support the gills (and are eventually lost in frogs). Somites are blocks of tissue that divide an embryo into segments that will become part of the vertebrae. The tail bud is tissue that helps form the posterior of the animal. 5. Compare: Go to stage 16. A. What structure does all five embryos have in common? The heart forms. B. What structures are missing from the frog and fish? The limb buds. Frogs are born as limbless tadpoles and their arms and legs develop later. 6. Compare: Go to stage 20. What structure does mice and humans have in common that are missing from the other organisms? The umbilical cord. 7. Discuss: Looking at the similarities and differences between the organisms throughout development, which organisms are more closely and more distantly related to one another? Explain. Human and mouse are more closely related. Fish and frog also are more closely related. 8. Think and discuss: How do the similarities and differences between embryos provide evidence that evolution has occurred? The difference in how some embryos developed limb buds at stage 16 and the umbilical cord at stage 20 shows evolution because prior to