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Biology 1010 Chapter 20

Biology 1010 Chapter 20. Bryophytes. Bryophytes. What are they?? Where are they found?? What is their evolutionary & ecological importance??. Points to Ponder. Differentiate the bryophyte phyla from each other and other phyla Describe the bryophyte adaptations to terrestrial environments

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Biology 1010 Chapter 20

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  1. Biology 1010Chapter 20 Bryophytes

  2. Bryophytes • What are they?? • Where are they found?? • What is their evolutionary & ecological importance??

  3. Points to Ponder • Differentiate the bryophyte phyla from each other and other phyla • Describe the bryophyte adaptations to terrestrial environments • Describe reproduction in bryophyte phyla • Describe the ecological role of bryophytes

  4. Kingdom Plantae • Bryophytes: simplest plants • Include liverworts, hornworts, mosses • Fossils from 400 mya • Molecular evidence suggests 700 mya • Economically important species • Sphagnum moss from peatlands • Cool northern areas: Canada, n. US, Ireland • Modifies soil to retain H2O, adds organic material • Fuel source • Acid pH or antibiotic compounds: aid wound healing

  5. Bryophyte Overview • Life on land possible when • Oxygen level > 2 % • Present oxygen level?? • Water can be retained • Bryophytes found in moist environments • Term refers to nonvascular plants • Formerly one phylum • Now: three phyla • Each evolved independently • From the same green algal ancestors

  6. Phylum Hepatophyta • Liverworts • 6000 spp • 1st land plant fossil 450 mya • Probably liverwort • Advantages of land: • Intense sunlight • Rocks rich in minerals

  7. Phylum Anthocerophta • 100 spp • Hornworts • Possible path of evolution: • Stranding of green algae with prior adaptations Adaptations include: vertical stems underground stems for H2O & nutrient uptake

  8. Phylum Bryophyta • 9,600 spp • Mosses • Bryophytes limited to moist environments • Sperm requires water • Just as amphibians do • Some can live in dry sites • Do not fossilize well • Molecular evidence • 700 mya

  9. Bryophyte characteristics • Nonvascular: no xylem & phloem • Restricts size, limits distribution on land • Gametophytes have structures • Resemble stems & leaves • Without internal ‘veins’ • Hydroids: conduct H2O • Leptoids: conduct food • Thallus: body of a bryophyte • Rhizoid: anchors bryophyte to substrate • Absorption occurs through contact

  10. Bryophytes similar to Charophyceae & vascular plants • Classification of algae & plants unsettled • Should reveal phylogeny • Similarities between charophyceae & plants • Cellulose in cell walls • Mitotic spindles remain during cytokinesis • Pigments: • Phytochrome, Chla, b, carotenoids, • Thylakoids stacked in grana

  11. Bryophytes similarity to plants • Characteristics that enhance survival on land • Protect gametes and spores • Sterile cells protect structures producing male and female gametes • multicellular embryo protected within female parent • Multicellular, diploid sporophyte meiosis → spores • Sterile cells protect multicellular sporangia • Natural selection guided bryophyte evolution from green algae differently than plants

  12. Bryophyte Alternation of Generations • Gametophyte dominant • Haploid • Gametangia: mitosis → gametes • Antheridia: male • Archegonia: female, one egg • Sporophyte attached to gametophyte • Depends on gametophyte for its nutrition • Diploid • Meiosis → haploid spores in sporangium • Spore germinates → protonema

  13. Bryophyte Asexual Reproduction • All 3 phyla can reproduce by fragmentation • Reproduce through specialized brood bodies • Gemmae • bulbils

  14. Ecological roles of Bryophytes • Plant succession • Mosses colonize rock surfaces, crevices • → soil • Rhizoids secrete acid to dissolve rock • Bodies add organic matter, collect dust • Seeds germinate in these pockets • Epiphytic mosses: • Grow in tropical and temperate rain forest trees • Important in tundra • NOT “reindeer moss” = lichen

  15. Bryophytes tolerate drought • Liverworts may roll into tube • Protects upper surface • Tortula spp • Moss can dehydrate • Produce mRNA • Codes for protein to repair damage • Rehydration → resumption of photosynthesis

  16. P. Hepatophyta= liverworts • Earliest land plants? • Closely related to green algae • Lack DNA characteristic of other bryophytes, plants • Horizontal, flatter than mosses • Leaves usually thin, flat • Categories: • Thalloid or leafy

  17. Liverwort life cycle • Gametophyte dominant • Marchantia • Lobed gametophyte large • Rhizoids penetrate soil • Antheridia & archegonia elevated • Antheridiophore flattened, bears antheridia, catch rain drops • Archegoniophore suspends archegonia beneath tops • Sporophyte inconspicuous • Zygote in archegonium • Forms spores

  18. P. Anthocerophyta= hornworts • Conspicuous horn-shaped sporophytes • Stomata with guard cells: new feature • Gametophytes similar to liverworts • Rumpled, green sheet • N-fixing bacteria symbionts

  19. Hornwort life cycle • Gametophyte form antheridia • Become visible when sterile cells dry & break • Archegonia form from surface cells • Thallus cells surround egg • Fertilization → zygote with ‘horn’ • Sporophyte foot anchors it to gametophyte • Gametophyte provides water, minerals, some food • Sporophyte grows from its base not its apex • photosynthetic as in liverworts, NOT mosses • Produces spores from apex of sporangium to base

  20. P. Bryophyta= mosses • bryophytes refers to ALL nonvascular plants • P. Bryophyta = scientific classification • Mosses usually with a leafy thallus • Vertical gametophyte • Usually in moist, forested sites, wetlands • Sometimes in deserts, dry rock outcrops • Some aquatic

  21. Class Spagnopsidaaka Sphagnidae • 150 spp, peat mosses • Sheet like protonema • Dead cells with thick walls hold water • spherical sporangia attach to stalks of gametophytes

  22. Class Andreaeopsida= granite or rock mosses • 100 spp • Live at high altitudes • Cold, temperate sites • Live on rock, snow, ice • Sporangia with four slits allow dispersal of spores

  23. Class Bryopsidaaka Bryidae • 9,000 spp • Common mosses • Growth patterns vary • May grow in clumps • As pendulous epiphytes • May remain filamentous • May be seasonal • May grow on polluted soil

  24. Life cycle of Polytrichum • Typical moss life cycle • Dominant gametophyte • Survives drought • Originates from spore • Spore → protonema • Bud → gametophyte leaf • → Antheridia &/or archegonia • Water → fertilization • Zygote develops in archegonium • → sporophyte with setae • foot absorbs food

  25. Questions • Thought and Discussion • 2 • 4 • Evolution Connection

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