Ch 9 Biological Diversity (AP)

Terms in this set (230)

1. Except for the primitive bryophytes (mosses, liverworts, and hornworts), the dominant generation of all plants is the diploid sporophyte generation. A diploid structure is more apt to survive genetic damage because two copies of each chromosome allow recessive mutations to be masked.
2. All plants possess a cuticle, a waxy covering on aerial parts that reduces desiccation.
3. The development of a vascular system in plants further reduced their dependency on water. Without a vascular system, all cells must be reasonably close to water. A vascular system reduced this dependency by providing a system for water to be distributed throughout the plant. Once cells were relieved of their dependency upon water, tissues specialized for specific tasks evolved. True leaves developed as centers for photosynthesis, true stems developed to provide a framework to support leaves, and true roots developed to obtain water and anchor the plant. Two groups of vascular tissues evolved, xylem and phloem. Xylem is specialized for water transport, and phloem is specialized for sugar transport.
4. In the more primitive plant divisions, flagellated sperm require water to swim to the eggs. In the more advanced divisions (Coniferophyta and Anthophyta), the sperm, packaged as pollen, are adapted for delivery by wind or animals.
5. In the most advanced division, the Anthophyta, the gametophytes are enclosed (and thus protected) inside an ovary.
6. Plants of the Coniferophyta and Anthophyta have developed adaptations to seasonal variations in the availability of water and light. For example, some trees are deciduous; that is, they shed their leaves to minimize water loss during slow-growing (or dormant) seasons. In contrast, desert annuals will germinate, grow, flower, and produce seeds within brief growing periods in response to a spring rain.