Lewis/Life - Review of Key Concepts

Review of Key Concepts - Chapter 25

Plants are multicellular eukaryotes that have cellulose cell walls, chloroplasts, and photosynthetic pigments and that use starch as a nutrient reserve. They have alternation of a sporophyte (diploid) phase and a gametophyte (haploid) phase in each generation. Plants are widely distributed and are essential to the survival of many other species.
Plants are classified by presence or absence of vessels and seeds. Bryophytes lack vessels. Vascular plants have vessels and may be seedless or produce seeds. Gymnosperms have naked seeds, and angiosperms have covered seeds.
Bryophytes are small green plants lacking vascular tissue, supportive tissue, and true leaves and stems. They resemble the earliest plants, which arose from algae. Lignin hardens bryophytes and rhizoids anchor them to the ground, where they absorb water and nutrients. Bryophytes reproduce both asexually and sexually. The gametophyte is dominant, and sexual reproduction requires water for sperm to travel through. Sperm from an antheridium travel to eggs in an archegonium. The three divisions of bryophytes are mosses, liverworts, and hornworts.
Seedless vascular plants share the same pigments, reproductive cycles, and starch storage mechanisms as bryophytes, but they differ in having conducting tissue and a dominant sporophyte generation. Xylem tissue carries dissolved nutrients and water, and phloem carries sugars. Seedless vascular plants are adapted to life on land and include whisk ferns, club mosses, horsetails, and true ferns.
The seed-producing vascular plants are the gymnosperms and angiosperms. Neither requires water for sperm to meet eggs. Gymnosperm seeds are not enclosed in fruits, and many lack vessels in the xylem. They have diverse leaves and reproductive structures. Gymnosperms include ginkgos, cycads, conifers, and gnetophytes. Angiosperms appear rather suddenly in the fossil record and rapidly diversified.