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Chapter 29: Plant Diversity

Chapter 29: Plant Diversity . How Plants Colonized Land. By: Meg Riley, Anna Ferlanti, and Laurie VanBenschoten. The Greening of Earth. Land plants evolved from aquatic green algae 500 mya Plants are crucial to life on Earth Supply Oxygen Provide Habitats Provide Food. Charophyceans

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Chapter 29: Plant Diversity

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  1. Chapter 29: Plant Diversity How Plants Colonized Land By: Meg Riley, Anna Ferlanti, and Laurie VanBenschoten

  2. The Greening of Earth • Land plants evolved from aquatic green algae 500 mya • Plants are crucial to life on Earth • Supply Oxygen • Provide Habitats • Provide Food Charophyceans (algal ancestor of land plants) http://greatneck.k12.ny.us/GNPS/SHS/dept/science/krauz/bio_h/images/29_03Charophyceans_LP.jpg

  3. Evolution from Algae • Aquatic green algae= charophyceans • closet living relative of land plants, share a common ancestor • First land plants were seedless • reproduced using spores

  4. Evidence for Common Ancestry • Morphological and Biochemical Evidence • Structure of flagellated sperm • Closely resembles that of charophyceans • Genetic Evidence • Nuclear & chloroplast genes suggest relatedness to charophyceans • Confirms conclusions from above

  5. Adaptations for Movement to Land • Adaptations enabling the Move to Land • A chemical found in both charophyceans & land plants Algae prevents zygote from drying out in exposed environments Plants encases spores

  6. The Plant Kingdom • Kingdom Plantae currently includes all embryophytes • Embryophytes= plants that grow from an embryo • excludes charophyceans

  7. Derived Traits of Land Plants • These traits, unique to nearly all plants, distinguish them from charophyceans • Apical meristems- localized regions of cell division that make vascular tissue • Alternation of generations- alternation between two multicellular body forms between generations • Walled spores produced in sporangia- multicellular capsules that contain and protect spores during development • Multicellular gametangia- multicellular organs in which gametes are produced • Archegonia- female, 1 egg • Antheridia- male, many sperm • Multicellular, dependent embryos- zygote retained within tissue of female parent and develops with nutrients from mother • Cuticle coverings- layer of polyesters & waxes that prevents plant from drying-out ***(see pg. 576-577 for full explanations)

  8. Evolutionary History of Land Plants

  9. Gametophyte vs. Sporophyte Gametophyte multicellular haploid form of a cell undergoing alternation of generations 1n Sporophyte multicellular diploid form of a cell undergoing alternation of generations 2n VS.

  10. Characteristics of Bryophytes • Bryophytes are seedless nonvascular plants • found in three plant phyla…phylum Hepatophyta (liverworts), Anthocerophyta (hornworts), and Bryophyta (aka moss) • Gametophyte is dominant over sporophyte • Bryophyte Gametophytes • Characteristics • Form ground-hugging carpets, low to the ground, short • Thin, approx. 1 cell layer thick • Bryophyte Sporophytes • Consist of 3 parts: • Foot- anchors to set into sporophyte • Seta (or stalk)- holds up sporangium • Sporangium (or capsule)- contains & protects spores • Ecological and Economic importance of Mosses • Mosses are widespread and important • Ex. Peat moss used as fossil fuel and good for preserving bodies in swamps

  11. : http://www.youtube.com/watch?v=jcWYAnmm-QE

  12. Life Cycle of Bryophyte (ex. Moss) • Spores develop into threadlike strands of plant fibers • The haploid strands produce “buds” that grow into gametophytes • Most mosses have separate male and female gametophytes with antheridia and archegonia respectively • A sperm swims through a film of moisture to an archegonium and fertilizes the egg • The diploid zygote develops into a sporophyte embryo within the archegonium • The sporophytes grows a long stalk, or seta, that emerges from the archegonium • Attached by its foot, the sporophyte remains nutritionally dependent on the gametophyte • Meiosis occurs and haploid spores develop in the sporangium of the sporophyte • Sporangium pops off, propelling spores into the air using “teeth”

  13. Characteristics of Lycophytes & Pterophytes • Origins and Traits of Vascular Plants • Life Cycles with Dominant Sporophytes • More sporangia, more spores, more evolutionarily fit to survive into adulthood • Transport in Xylem and Phloem (type of vascular tissue) • Xylem-conducts water & minerals • Phloem- conducts sugar, amino acids, and other organic products • Evolution of Roots • Roots –anchor plant, allow for absorption of water and nutrients from soil • Evolution of Leaves • Leaves- increase surface area, allow capture of more sunlight for photosynthesis, increase plant efficiency • Mircohpylls- leaves of old lycophytes • Megaphylls- leaves of new lycophytes, more complex

  14. Characteristics of Seedless Vascular Plants (cont.) • Sporophylls and Spore Variations • Sporophylls (modified leaves with sporangia) • Homosporous vs. Heterosporous • Megaspores vs. Microspores

  15. Life Cycle of a Lycophyte (ex. Fern) • Sporangia release spores • Spore develops into photosynthetic gametophyte • Cross or self- fertilization may occur between male and female gametes • Sperm use flagella to swim from antheridium to archegonium • Sporophyte grow out of archegonium of gametophyte • Spores form in clusters on underside of reproductive leaves (sorus)

  16. Classification • Phylum Lycophyta: older seedless vascular plants, common ones include spike & club mosses (not true mosses) • Phylum Pterophyta: younger seedless vascular, all sorts of ferns Spike/Club Moss Fern http://kmacphoto.net/ferns.jpg http://www.sd23.bc.ca/~mbirkela/FOV1-000ABDA6/S0A59B017.4/tips-for-sorting-through-ferns0.jpg

  17. Significance • How evolution of vascular tissue, roots, and leaves allows plants to grow bigger than ever before…development of large forests • Increased removal of CO2 from atmosphere, resulting in global cooling • Plants fossilize to from coal, however, once coal is burned as fossil fuels, it results in global warming

  18. Answers to Activity: • Part 1- Moss 5 2 6 3 1 7 8 4 • Part 2- Fern 2 6 3 4 1 5

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