Plant-Animal Adaptations
Plants and animals often evolve by adapting to each other; for example, plants evolve defenses against herb ivory (animals feeding on plants).Spiny cacti, poisonous hemlock, thorny rosebushes, and prickly thistles are all familiar examples of defended plants. A more unusual and particularly unpleasant defense is used by plants in the milkweed family, which get their common name because their leaves and stems, when cut, ooze a white sap. However, only in appearance is the sap milky-it is sticky and thick and, in many species, it has chemical irritants that make it even more noxious to touch or taste. Nevertheless, many insects are able to feed on milkweed. Milkweed beetles overcome this defense in an innovative way by biting repeatedly into the midrib central vein) of the milkweed leaf. The sap leaks out through the bite holes before it reaches the tips of the leaves, where the beetle can then feed without its mouthparts becoming too full and sticky. This isn’t good for the plant because midrib cutting and feeding reduce the plant’s ability to photosynthesize (convert sunlight into chemical energy for food)
While roots, stems, and leaves are often defended, fruits and flowers have evolved to attract animals. Most ripe fruit is red or black, such as raspberries and blackberries. Is this because these colors have evolved to attract frugivores ( fruit eaters) that will disperse the seeds? Birds, 0ne of the main frugivores have four types of retinal cones (cells responsible for Seeing color) that give them excellent color vision. Foraging birds do prefer red and black fruits-but not because they are attracted to the color itself. Instead, red and black fruits contrast well with the typical green background of foliage, and it is this contrast that attracts birds.
Flowers have also evolved visual cues attractive to pollinators. Many
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