Diversity 2

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Diversity 2
2010-10-05 22:18:22

evolution of land plants
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  1. A megaspore is...?
    a female spore
  2. A microspore is...?
    a male spore
  3. Plants are...
    Multicellular, photosynthetic eukaryotes that range in size from the duckweed to the giant coastal redwoods.
  4. When did plants evolve? What evidence?
    • believed to have evolved from freshwater green algae over 500 million years old.
    • Contain chlorophylls a and b and various accessory pigments.
    • Store excess carbohydrates.
  5. Green Algae ancestry. How is this known?
    • terrestrial plants arose from a green algal ancestor.
    • both have the same photosynthetic pigments (chlorophyll a and b)
    • some green algae have a cell wall made of cellulose
    • cells divide similarly
  6. Algae division
    • Chlorophyta
    • largest and most diverse group of algae
    • Habitat: found mostly in fresh waters and on land
    • Float in rivers, lakes, resevoirs, creeks
    • Can also live on rocks, trees, soil
  7. Plants evolved from algae
    • algae cannot survive on land
    • plants adapted characteristics
  8. Earliest known land plant...
    • Cooksonia
    • nonvascular and similar to today's bryophytes
  9. Probable alga ancestor
    • Coleochaete
    • both have same pigments (chlorophyll a and b, carotenes, etc.)
    • both use starch to store photosynthetic products
    • both have cellulose in their wall
    • both have alternation of generations
    • both form a cell plate during cell division
  10. Adaptations for plants to obtain enough water
    • plants evolved roots to anchor the plant
    • roots to absorb water and dissolved minerals
  11. Adaptation to preventing water loss
    • plants evolved a cuticle- waxy layer
    • evolution of multicellular gametangia (sex organs)- helped protect gametes from drying out.
    • evolution of a resistant coat on spores that prevents drying out
  12. Adaptations to getting enough energy
    • In land, plants obtained enough sunlight for photosyntsis
    • different strategies for obtaining light
    • -growing taller and taller above other plants- plants began to evolve support cells
    • -others had to adapt to lower light intensities
  13. Bryophyte Characteristics
    • nonvascular
    • such as mosses
  14. Trachophyte characteristics
    • vascular (xylem and phloem)
    • ferns and fern allies
    • seed plants
  15. Photosynthetic (water) dilemma
    • Problems- plants need pores for gas exchange for photosynthesis, but open pores (stomata) allow water to leave (95% water taken is lost)
    • solution- stomata open during the day (for photosynthesis gas exchange) and close during the night (to allow platn to recover from water loss)
  16. Affects of having multicellular organism
    • advantages: roots better, protect gametes, grow tall to obtain sunshine
    • disadvantage: getting water to all cells
  17. Vascular tissue
    • Xylem:
    • Phloem:
  18. Algae vs Plant Life Cycle
    • algae: water dependent life cycle.
    • plants: water independent life cycle in land plants. plants developed dry-resistant gametophytes (spores) or zygotes (seeds).