- structures that are present in an organism yet have no apparent function - example: hipbones found in whales and snakes, and the appendix in humans.

- were four-footed, landdwelling creatures. - Fossils of now extinct whales show that they had rear flippers that contained leg bones. - Present-day whales do not have rear appendages but do have hipbones left from their ancestors.

- were amphibian-like creatures that had four legs. - Boa constrictors have vestigial hipbones where legs would have been. There are other types of snakes that have protrusions where vestigial hipbones are.

- The early mammals were thought to be small herbivores (plant-eating animals). - Herbivores have an organ called the cecum that holds bacteria able to digest cellulose, a material found in the cell wall of plants. Herbivores cannot digest cellulose, and thus, it is beneficial for them to have a cecum where bacteria can live and digest cellulose for them.

- (meat eaters and plant and meat eaters) have a reduced cecum. - The cecum was selected against in carnivores because it wasn’t necessary and was an additional body part with additional risks (it holds bacteria). The remnant of the cecum is the appendix

Which of the following is not an accurate explanation for the existence of the indicated vestigial structure?

- The tail on a peacock was once used as a weapon and distraction during confrontation but no longer serves a purpose.

Vestigial structures occur because

- the structure conferred no adaptive advantage to the species in which it is functionless, and it may have had disadvantages. - evolution is a slow process, and useless structures do not disappear quickly.

1.7.2 Evidence for Evolution: Vestigial Structures Flashcards by Irina Soloshenko

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1.7.2 Evidence for Evolution: Vestigial Structures Flashcards

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