The wing of a bird and the leg of a horse are very different looking structures. although they look different, bird wings and horse legs are very similar in the arrangement of the bones that make up the limb. which term is used by scientists to describe structures that look different on the outside but are actually similar in construction and develop from the same embryonic tissues?
a) common descent
b) ancillary anatomy
c) vestigial structures
d) homologous structures

Juan and carol were studying invertebrates in biology. they knew that segmented or earth worms preferred a dark, moist habitat. during this lab, they would be investigating the responses of organisms called planaria or dugesia tigrina. these were simple flatworms that still had a one-way digestive system and a very simple nervous system. juan and carol placed the planaria in a petri dish containing cool, distilled water that was partially covered with black paper. they shined a light on the dish. next, they removed the paper and placed a small amount of chicken liver at one end of the dish. they added a few large salt crystals to the water. finally, they added drops of hot water to the cool water in the petri dish. their results can be seen in the data table. according to their experiment, all but one conclusion is valid.