Vascular plant diversity animals could not move onto

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Vascular Plant Diversity Animals could not move onto land before the plants did. Plants that emerged onto land during the Ordovician rapidly evolved vascular tissue for
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transporting water and nutrients. The figure below shows a family tree of the green vascular plants, with their approximate divergence times. At the present time the angiosperms (flowering plants), with their double fertilization mechanism, dominate the world of land plants. Double fertilization takes place in the angiosperms (diagram below). It has the great advantage that the storage materials in the seed endosperm only begin to develop when the egg itself is fertilized. If the endosperm of unfertilized eggs also developed, the plant would waste energy manufacturing this unneeded food. Double fertilization is an important reason why the angiosperms have been so successful since their origin in the early Mesozoic, and are so widespread
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today. There are currently 250,000 species. The gymnosperms (evergreen trees and their allies) arose earlier, during the Carboniferous. They have fallen from large numbers of species during the Mesozoic to only 400 species worldwide at the present time.
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This Banksia prionotes , from western Australia, illustrates the value of double fertilization. Although there are many individual flowers in an inflorescence (the flower in the back), the rate of pollination by birds and insects is low (the mature flower or infructescence in the front). As a result, few seed pods form. If the plant had to develop seed pods even from unfertilized flowers, it would waste resources.
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