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Plant Diversity I and II

Plant Diversity I and II. Labs 6 and 7 BIOL 171. Introduction. First land plants were related to green algae – 500 million years ago. Plant Life Cycles. All land plants have a common sexual reproductive life cycle called alteration of generations Gametophyte – haploid (n) generation

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Plant Diversity I and II

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  1. Plant Diversity I and II Labs 6 and 7 BIOL 171

  2. Introduction First land plants were related to green algae – 500 million years ago

  3. Plant Life Cycles • All land plants have a common sexual reproductive life cycle called alteration of generations • Gametophyte – haploid (n) generation • Sporophyte – diploid (2n) generation • One generation is always dominant (more conspicuous) • In the Bryophytes (mosses and liverworts) the gametophyte is dominant • In all other land plants the sporophyte is dominant

  4. Alteration of Generations(also look at figure 2 in lab manual)

  5. Alteration of Generations Vocab • Spores – (n) produced by the sporophyte generation through meiosis – germinate to produce the gametophyte (n) • Sporangium – a protective nonreproductive jacket that contains the spores • Gametes – produced inside the gametangia located on the gametophyte • Eggs (n)are produced inside the archegonia through mitosis • Sperm (n) are produced inside the antheridium through mitosis • Zygote – (2n) formed by fusion of the gametes, this is the first stage of the sporophyte generation

  6. Bryophytes • 3 divisions (phyla): Bryophyta(mosses), Hepatophyta (liverworts), and Anthocerophyta(hornworts). • Small plants, lacking vascular tissue (specialized cells for transport of material) • The gametophyte generation is dominant and conspicuous plant. • Restricted to moist habitats • Both because they lack vascular tissue • And because this enables their mobile sperm to swim and fertilize the egg • Have a cuticle, but lack stomata on the surface of the thallus(plant body)

  7. Bryophyta(mosses) • Most common group • Occurs in moist environments, but also found in dry habitats that are periodically moist Peat moss (Sphagnum)

  8. Alternation of generations (mosses) GAMETOPHYTE (n) SPOROPHYTE (2n) Ovum (gametangia) Sperm Gametophyte Sporophyte (2n) Embryo (2n) Spore (n) Gametophyte (n)

  9. Hepatophyta(liverworts) • Flattened and lobed thallus (plant body) • Early herbalists believed that these plants were could treat liver disorders. • Found along streams on moist rocks • Very small

  10. Liverwort body form • Rhizoids – rootlike extensions on the lower surface of the thallus • There are pores on the leaflikethallusthat function in gas exchange, but lack guard cells so are always open. • Gemmae cups are located on the upper surface of the thallus, they are circular cups that contain flat disks of green tissue called gemmae. • The gemmae are washed out of the cups when it rains, and they grow into new, genetically identical liverworts.

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