Plants ch 24

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Plants ch 24

  1. 1. Reproduction with cones and flowers• Alternation of generations• Diploid sporophyte generation alternates with haploid gametophyte generation
  2. 2. Life Cycle of gymnosperms• Takes place in cones, which are produced by a mature sporophyte• Pollen cones - male – pollen grains• Seed cones – female – ovules - which develop into a new embryo following fertilization
  3. 3. Structures of Flowers• Sepals – protection during development• Petals – located inside sepals, used to attract pollinators• Stamens – male parts consisting an anther and filament,• filament – long stalk that supports the anther• Anther – oval sac where meiosis takes place
  4. 4. Cont.• Carpels – innermost floral part – (pistils) where ovary produces gametophytes• From the ovary, a stalk extends narrowing into the style, at the top is the sticky stigma
  5. 5. Life cycle of angiosperms• Reproduction takes place within the flower. Following pollination and fertilization, the seed develop inside protective structure• Pollination for most angiosperms is by animals
  6. 6. Fertilization• Occurs when pollen lands on same species, pollen tube grows into style releasing two sperm nuclei• 1 Sperm fuses with egg to produce diploid zygote, 2nd fuses with nuclei in embryo-sac which will grow into food-rich tissue called endosperm
  7. 7. Seed development and germination• Angiosperm seeds mature the ovary walls thicken to form a fruit that encloses the developing seed• Seeds dispersed by animals are typically contained in fleshy, nutritious fruits• Wind and water require seeds that are lightweight to be carried or float
  8. 8. Cont.• Dormancy – seed is alive, just not growing• Factors like temperature and water can change dormancy• Germination – seed absorbs water, cracking open seed coat, roots emerge and seed begins to grow
  9. 9. Plant Propagation• Vegetative reproduction includes the production of new plants from horizontal stems, from plantlets, and from roots• Plant propagation –cuttings, grafting or budding is use to make many identical copies of a plant or to produce offspring from seedless plants
  10. 10. Agriculture• 10,000 to 12,000 – people began to harvest food• Most people world wide depend on a few crops; wheat, rice, corn

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