Unit 5 _student fall 2008

Unit 5 _student fall 2008 - 1 Plant Evolution and Basic...

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Plant Evolution and Basic Structure I. Evolution of plants (in order of appearance) A. Bryophytes – have no vascular tissues meaning no xylem or phloem; no xylem = no rigid support = cannot grow tall 1. Properties: a. Have a cuticle_ to prevent water loss b. Jacket of cells protect ___gametes___ c. They are _embryophytes (embryo begins development attached to and nourished by the parent plant)___ d. Sperm require: water for fertilization (need to swim through water like fish and amphibians) 2. Ex: mosses 3. Evolutionary advantage: do not need to be immersed in water*__ at all times because of the _*cuticle*__ (although they require moisture); could ensure better survival of the: _*gametes and embryo*____ B. Seedless vascular plants 1. Additional properties (compared to bryophytes): have xylem and phloem; xylem contains lignin (wood) in cell walls * Note: moisture is still required for reproduction because: sperm still need water for dispersal 2. Ex: ferns 3. Evolutionary advantage- growing tall; avoid predators; access sunlight more easily C. Gymnosperms - naked seed (seed dispersal dependent on the wind) 1. Additional Properties: (compared to seedless vascular plants) a. Sperm dispersal- as pollen (by wind) 1
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tough protective coating) 2. Ex: pine trees 3. Evolutionary advantages – * -seed perfectly designed to float in the wind - could colonize dry land; do not need water for sperm dispersal -fertilization is protected and occurs inside the female’s ovule -seed provides protection and nourishment for the embryo -could survive earth’s cold temperatures bc of needles D. Angiosperms – ‘vessel seeds’ = flowering plants 1. Additional Properties (in addition to the properties of Gymnosperms) a. Have seeds that develop in protective chambers called _FRUIT b. _FLOWERS (temporary reproductive structures)____________produced to attract pollinators (although some dispersal may also be through wind and water). 3. Ex: majority of plants (daphodils, fruit trees, etc.) 4. Evolutionary advantages – a. _TARGETED_ pollination by animals is far more efficient than leaving pollination up to chance in the wind. b. __WIDE__ dispersal of seeds via _FRUIT__. Various dispersal mechanisms. c. Reproduce _QUICKLY__- unlike gymnosperms which may take two years to go from pollination to seed, many angiosperms can reproduce quickly to take advantage of a short growing season (ex: a short rainy season in the desert). 2
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Unit 5 _student fall 2008 - 1 Plant Evolution and Basic...

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