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Plant Evolution

Plant Evolution

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Plant Evolution

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  1. Plant Evolution

  2. Plants • Origins over 700 MYA • 10 Divisions • 4 Basic lifecycles • Green algae that evolved onto land • Evolved for more independence from water • Then coevolved with pollinators, dispersal • Major events: • Living on land, spores • Vascular tissues • Seeds • Flowers & Fruits

  3. Plant Evolution • Green Algae gave rise to: • Mosses and liverworts, which gave rise to: • Ferns and related plant groups which gave rise to: • Conifers and related plant groups which gave rise to: • Angiosperms (flowering plants) which have form two groups: • Monocots • Eudicots

  4. Segregation of Nutrients Minerals & H2O Light & CO2 Gravity Increase in Height Dessication Tissues Gametes Dispersal Regional specialization Root system Shoot system Lignin & cellulose Vascular tissue Specialized structures Cuticle Sporophyte dominance Dispersal mechanisms Seeds Pollen Symbiosis Colonization of Land Challenges… Problems Solutions

  5. Characteristics of Plants • Growth by divisions in Apical Meristems • Alternation of generations • Dependent embryos • Spores • Cuticle • Transport tissues • Secondary compounds

  6. Growth at Apical Meristem

  7. Alternation of Generation

  8. Switch to sporophyte dominance

  9. Dependent Embryos • Placental Transfer cells feed embryo from parent tissue

  10. Spores • Walls of resistant sporopollenin • Dry out and travel in the wind • Disperse then grow into gametophyte plants

  11. Cuticle • Waxy covering layer prevents water loss and microbial attack • Stomata allow for gas exchange • Thicker layers in plants adapted to arid conditions

  12. Charophyceans- Share ancestry with plant’s green algae ancestor CharaColeochaete Modern examples of charophyceans

  13. Transport Tissues • Xylem carries water up from the roots to the leaves • True xylem has rigid cell walls with lignin • Cells are dead and hollow to function • Makes up wood • Phloem carries a sugary solution through out the plant • Soft living tissue

  14. Vascular tissue • Allows plants to grow taller • More support by lignified xylem tracheids • Can pull water up from soil • Can tolerate soil that is drier on the surface • Form parts of true leaves and roots. • Only found in diploid tissue • Lead to sporophyte dominance?

  15. Plant Groups • Division Bryophyta • Mosses, liverworts, & hornworts • Division Pterophyta • Ferns, horsetails • Division Coniferophyta • Conifers • Division Anthophyta • Flowering plants

  16. General Bryophyte Characteristics • All haploid dominant • Motile sperm • Limited to moist environments • Small size • Lack vascular tissue • Lack stomata • No true plant tissues (leaves, roots, stems) • Have cuticle

  17. Bryophyte lifecycle: moss • Polytrichum spp • Haploid dominant • Dioecious or monoecious gametophytes • Swimming sperm • No true leaves • No mesophyll, stomata, veins • No vascular tissues • Phyllidia • No true roots • Rhizoids • Dependent sporophyte • Disperse by spores • Filamentous protonema stage

  18. Gametophyte Phyllidia = leaf like structures

  19. Male Gametophyte

  20. Sperm

  21. Female Gametophyte

  22. Sporophyte

  23. Moss Sporangia

  24. Sporophyte with Sporangia

  25. Liverworts Hepatophyta • Marchantia sp • Thallus • Leaf-like body • Gametophyte • Asexual Reproduction • Gemmae cup • Sexual reproduction • Gametophore • Dioecious gametophytes • Antheridiophore- male • antheridia • Archegoniophore- female • archegonia

  26. Thallus

  27. Gemmae Cups

  28. Gemmae Cups

  29. Male & Female

  30. Antheridiophore

  31. Archegoniophore

  32. Archegoniophore

  33. Liverwort Sporangia • On undersides- develop from archegonia

  34. Vascular Tissue • Allows plants to grow taller • More support by lignified xylem tracheids • Can pull water up from soil • Can tolerate soil that is drier on the surface • Form parts of true leaves and roots. • Only found in diploid tissue • Lead to sporophyte dominance? • Gametophytes progressively smaller

  35. Seedless Vascular Plants • 400 MYA • Seedless, Vascular plants (having Xylem & Phloem). Today represented by four divisions: • Division Pterophyta- Ferns • Division Lycophyta- Club Mosses • Division Sphenophyta- Horsetails (Equisetum) • Division Psilophyta- Whisk ferns

  36. Pteridophytes • Diploid dominate • Vascular tissue • Seedless • Cuticle, stomata • Swimming sperm • True roots and leaves • Pterophyta- fronds (megaphylls), sori, annulus • Lycophyta- microphylls, strobilus w/ sporophylls, heterosporus- megasporangium w/ megaspores, microsporangia w/ microspores • Gametophyte still independent, short lived, • monoecious in fern (Pteridophyta) • dioecious in club “moss” (Lycophyta) • Spores disperse plant • Sporophyte perennial

  37. Fern Lifecycle

  38. Fern Sporangia - Sori

  39. Annulus Sporangium Indusium