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General Biology: Plant Characteristics and Life Cycles

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Termini in questo insieme (25)

  • What are the five key derived traits of plants absent in green algae?
    Heteromorphic alternation of generations, multicellular dependent embryos, walled spores produced in sporangia, multicellular gametangia, and apical meristems.
  • Define alternation of generations in plants.
    Plants alternate between a haploid gametophyte generation producing gametes by mitosis and a diploid sporophyte generation producing spores by meiosis.
  • What is the ploidy and role of the sporophyte?
    The sporophyte is diploid (2n) and produces haploid spores by meiosis.
  • What is the ploidy and role of the gametophyte?
    The gametophyte is haploid (n) and produces haploid gametes by mitosis.
  • How do plant embryos depend on the parent?
    Plant embryos are retained within female gametophyte tissue and receive nutrients via placental transfer cells, making plants embryophytes.
  • What is the function of sporangia in plants?
    Sporangia are organs where diploid sporocytes undergo meiosis to produce haploid spores with resistant walls containing sporopollenin.
  • What are gametangia and their types?
    Gametangia are multicellular organs producing gametes: archegonia produce eggs, and antheridia produce and release sperm.
  • What is the role of apical meristems?
    Apical meristems sustain continual growth by repeated cell division, producing cells that differentiate into various tissues.
  • What are bryophytes and their major characteristics?
    Bryophytes are nonvascular plants (liverworts, mosses, hornworts) with dominant gametophytes, small size, and dependence on water for sperm motility.
  • How do bryophyte sporophytes differ from gametophytes?
    Bryophyte sporophytes are smaller, simpler, and dependent on the gametophyte, which is the dominant, longer-living generation.
  • What adaptations allowed seedless vascular plants to grow tall?
    Vascular tissue (xylem and phloem) enabled transport of water and nutrients and provided structural support for increased height.
  • What are the two types of vascular tissue and their functions?
    Xylem conducts water and minerals and provides support; phloem distributes sugars and organic nutrients.
  • What are microphylls and megaphylls?
    Microphylls are small leaves with a single vein; megaphylls are larger leaves with a branched vascular system.
  • What are sporophylls?
    Sporophylls are modified leaves that bear sporangia; clusters of sporangia are called sori, and groups of sporophylls can form strobili.
  • Define homospory and heterospory.
    Homospory produces one spore type developing into bisexual gametophytes; heterospory produces microspores and megaspores developing into male and female gametophytes.
  • What are the four common traits of seed plants?
    Seed plants have reduced gametophytes, heterospory, ovules, and pollen.
  • Why are gametophytes reduced in seed plants?
    They are microscopic and develop within spores retained in sporophyte tissues, protecting them and allowing nutrient transfer.
  • What is an ovule in seed plants?
    An ovule consists of a megasporangium, megaspore, and protective integuments; gymnosperms have one integument, angiosperms usually two.
  • What is pollen and its evolutionary advantage?
    Pollen grains contain male gametophytes; pollen allows sperm delivery without water and can be dispersed by wind or animals.
  • What evolutionary advantages do seeds provide?
    Seeds protect embryos, provide stored food, can remain dormant until conditions are favorable, and enable long-distance dispersal.
  • What are the key features of the gymnosperm life cycle?
    Miniaturized gametophytes, seed production, and sperm transfer to ovules by pollen.
  • What are the key features of the angiosperm life cycle?
    Miniaturized gametophytes, flowers to attract pollinators, seed production, pollen transfer via pollinators, double fertilization, and fruit formation.
  • What is double fertilization in angiosperms?
    One sperm fertilizes the egg forming a diploid zygote; another sperm fertilizes two polar nuclei forming triploid endosperm.
  • What is the role of fruits in angiosperms?
    Fruits develop from the ovary wall, protect seeds, and aid in seed dispersal by various mechanisms.
  • How do animals influence plant evolution?
    Animal herbivory selects for plant defenses; pollinators and plants coevolve mutually beneficial adaptations.