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biology 0610printed 247 · PDF 247
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● Although many plants may show some of these adaptive
features, xerophytes show them to a greater extent.
Adaptive features of hydrophytes
● Plants that live in very wet places, or in water, are called
hydrophytes. Their adaptive features help them to survive in water.
● The roots of hydrophytes do not attach to the bottom of the
water but rather float freely in the river or pond where they grow.
● The stems and leaf stalks have hollowed spaces filled in them,
filled with air to help them float on top of the water and get light for
photosynthesis.
● They have stomata on the upper surfaces as well as lower
surfaces. This is because the upper surface receives light from the
Sun so photosynthesis can take place. It also has no need to
conserve water so stomata don’t need to be hidden away from the
light.
● Some hydrophytes may also have thin, feathery leaves that can
spread out easily and absorb sunlight.
Natural Selection
● The process in which individuals with advantageous features
survive and pass on genes to the next generation, is called natural
selection.
● Natural selection can be summarized in five points:
1.
Variation: There is genetic variation within a population of
organisms which affects their adaptive features.
2.
Overproduction: Within a wild population, many more wild
offspring are produced than will survive to become adults and
reproduce.