Earland Plant Evolution Trends

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Earland Plant Evolution Trends

  1. 1. PLANT EVOLUTION Evolutionary Trends Bryophytes The rise of the vascular plants The rise of the seed plants
  2. 2. KINGDOM PLANTAE <ul><li>General features: </li></ul><ul><ul><li>Eukaryotic, multicellular, photosynthetic autotrophic organisms </li></ul></ul><ul><ul><li>P.S.= H2O + CO2+ sunlight  oxygen + sugar </li></ul></ul><ul><ul><li>C.R. = sugar + O2  CO2 and H2O + NRG </li></ul></ul><ul><li>Origins = blue-green bacteria  ancestral green algae  algae  bryophytes  tracheophytes </li></ul>
  3. 3. THE PHYLA <ul><li>Phyla grouped into: </li></ul><ul><li>- Nonvascular plants (lack true (lignified) vascular tissue) </li></ul><ul><li>- Seedless vascular plants (true vascular tissue (phloem and xylem), but reproduce only by spores (no seeds made) </li></ul><ul><li>- Seed bearing vascular plants </li></ul>
  4. 4. SETTING THE STAGE <ul><li>Earth’s atmosphere was originally oxygen free </li></ul><ul><li>Ultraviolet radiation bombarded the surface </li></ul><ul><li>Photosynthetic cells produced oxygen and allowed formation of protective ozone layer </li></ul>
  5. 5. PIONEERS IN A NEW WORLD <ul><li>Cyanobacteria were probably first to produce oxygen </li></ul><ul><li>Later, green algae evolved and gave rise to plants </li></ul>
  6. 6. ADVANTAGES AND DISADVANTAGES OF LIFE ON LAND <ul><li>Sunlight unfiltered by water and plankton </li></ul><ul><li>Atmosphere had more CO2 than water </li></ul><ul><li>Soil was rich in mineral nutrients </li></ul><ul><li>Originally relatively few herbivores and pathogens </li></ul><ul><li>Relative scarcity of water </li></ul><ul><li>Lack of structural support against gravity </li></ul><ul><li>Advantages: </li></ul><ul><li>Disadvantages: </li></ul>
  7. 7. EARLY PLANTS
  8. 9. EVOLUTIONARY TRENDS IN PLANTS STRUCTURE: <ul><li>Plants came from the sea which support, keep temp constant, bath whole plant with nutrients </li></ul><ul><li>Adaptations to terrestrial Life = </li></ul><ul><ul><li>Roots to anchor and absorb </li></ul></ul><ul><ul><li>Conducting vessels xylem & phloem to carry nutrients up and glucose around </li></ul></ul><ul><ul><li>Stiffening ligin to support the plant </li></ul></ul><ul><ul><li>Waxy cuticle on leaves and stem to prevent evaporation </li></ul></ul><ul><ul><li>Stomata pores in leaves to allow gas exchange, but close to prevent water loss </li></ul></ul>
  9. 10. ADAPTATIONS TO LAND <ul><li>Root systems – underground absorptive structures evolved as plants colonized the land </li></ul><ul><li>Shoot systems – evolved where stems and leaves intercepted sunlight energy and took in CO2 from the air. </li></ul>
  10. 11. ADAPTATIONS TO LAND <ul><li>Vascular tissues - evolution of roots and shoots forming components – xylem and phloem for transporting water and sugars to all tissues. </li></ul><ul><li>Waxy cuticle – evolved to assist plant to conserve water on dry, hot days. </li></ul><ul><li>Stomata – evolved to allow control of water loss and transport of gases. </li></ul>
  11. 12. EVOLUTIONARY TRENDS IN REPRODUCTION: <ul><li>Algae reproduce in water so gametes are carries by water, form zygotes in water and disperse in water. Ie No protection from dehydration required </li></ul><ul><li>Land plants needed: </li></ul><ul><ul><li>Transport gametes (pollen, flowers) </li></ul></ul><ul><ul><li>Protection from drying out (seeds) </li></ul></ul><ul><ul><li>Dispersal (seed coats & fruits) </li></ul></ul>
  12. 13. EVOLUTIONARY TRENDS IN PLANT LIFE CYCLES: <ul><li>Alternation of Generations = haploid gametophytes produces sex cells by mitosis. Gametes unite to from a diploid zygote, which develops into diploid sporophyte that develops haploid spores by meiosis </li></ul>
  13. 14. HAPLOID TO DIPLOID <ul><li>Gametophyte </li></ul><ul><ul><li>Haploid gamete producing body </li></ul></ul><ul><li>Sporophyte </li></ul><ul><ul><li>Diploid product of fused gametes </li></ul></ul><ul><li>Spore </li></ul><ul><ul><li>Resting structure </li></ul></ul><ul><ul><li>The most recently evolved groups produce seeds and pollen grains which were the key innovations that allowed the seed plants to spread widely into diverse habitats. </li></ul></ul>
  14. 16. EVOLUTIONARY TREND zygote SPOROPHYTE (2 n ) GAMETOPHYTE ( n ) GREEN ALGAE BRYOPHYTE FERN GYMNOSPERM ANGIOSPERM Relative size Life span
  15. 17. GENERAL TREND = DECREASED SIZE, DURATION, AND PROMINENCE OF GAMETOPHYTE GENERATION RELATIVE TO SPOROPHYTE <ul><li>Algae = some have no sporophyte or only the zygote </li></ul><ul><li>Mosses = gametophyte is green leafy and sporophyte is small and short lived </li></ul><ul><li>Ferns = sporophyte is the fronds of the ferns, gametophyte is smaller yet independent </li></ul><ul><li>Seeded plants = male and female gametophytes are microscopic and produce gametes to form sporophyte embryo </li></ul><ul><li>Recall: evolution occurs because of advantageous traits being selected therefore what is the advantage of diploid sporophyte dominance? </li></ul>
  16. 19. SPOROPHYTE <ul><li>The generation in the life cycle of a plant that produces spores. </li></ul><ul><li>Is diploid but its spores are haploid. </li></ul><ul><li>Either completely or partially dependent on the gametophyte generation in mosses and liverworts, but is the dominant plant in the life cycle of clubmosses, horsetails, ferns and seed plants. </li></ul>
  17. 20. LE 29-9D Polytrichum commune, hairy cap moss Sporophyte Gametophyte

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