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Homology: Leave It To the Plants

In the following photos of plants, the leaves are quite different from the "normal" leaves we envision.

Leaf homology

Each leaf has a very different shape and function, yet all are homologous structures, derived from a common ancestral form. The pitcher plant and Venus' flytrap use leaves to trap and digest insects. The bright red leaves of the poinsettia look like flower petals. The cactus leaves are modified into small spines, which reduce water loss and can protect the cactus from plant-eaters.

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