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Unformatted text preview: 1 http://guidesbyjulie.blogspot.com/ AP Biology Plant Highlights DISTINGUISHING CHARACTERISTICS OF PHYLA The four main groups of land plants are the bryophytes, pteridophytes, gymnosperms, and angiosperms. Bryophytes Bryophytes Bryophytes Bryophytes are different from algae in that they have several evolutionary adaptations to living on land, most of which are reproductive. This group includes liverworts, hornworts, and mosses. The group of vascular plants vascular plants vascular plants vascular plants consists of plants with vascular tissue vascular tissue vascular tissue vascular tissue, in which cells are joined into tubes that transport water and nutrients throughout the plant body. The pteridophytes pteridophytes pteridophytes pteridophytes, the group containing lycophytes, ferns, and horsetails, are sometimes referred to as seedless plants because they have no seed stage in their life cycle. In contrast, the gymnosperms gymnosperms gymnosperms gymnosperms and angiosperms angiosperms angiosperms angiosperms are seed plants. Seeds Seeds Seeds Seeds are plant embryos packed with a food supply into a protective coat. Examples of gymnosperms are ginkgos, cycads, and conifers. Most modern-day plant species are angiosperms, also known as flowering plants. ADAPTATIONS OF LAND PLANTS Apical Meristems Terrestrial plants need light and carbon dioxide from the air, while also requiring water and mineral nutrients in the soil. As a result, most plants have roots and leaf-bearing shoots to allow for maximum exposure to environmental resources. Growth in length is sustained by the activity of apical apical apical apical meristems meristems meristems meristems, localized regions of cell division at tips of shoots and roots. The cells produced by these meristems differentiate into a plants various tissues and also generate leaves in most plants. Multicellular, Dependent Embryos Zygotes that are kept within tissues of the female parent give rise to multicellular plant embryos, which are provided with nutrients from the parental tissues. The embryo has placental transfer cells placental transfer cells placental transfer cells placental transfer cells that enhance this transfer of nutrients. This is similar to the system in placental mammals. Land plants are also known as embryophytes embryophytes embryophytes embryophytes, a distinction recognizing multicellular, dependent embryos as a derived characteristic common to the land plant clade. Alternation of Generations The gametophyte and sporophyte generations are the two multicellular body forms that alternate in the life cycle of land plants. Cells of the gametophyte gametophyte gametophyte gametophyte are haploid and produce gametes. Fusion of eggs and sperm during fertilization results in diploid zygotes. Mitotic division of the zygote results in the multicellular, diploid sporophyte sporophyte sporophyte sporophyte. Meiosis in a mature sporophyte will result in haploid reproductive cells called spores. reproductive cells called spores....
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- Spring '08
- AP Biology