Angiosperms and reproduction
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  • 1. REPRODUCTION IN ANGIOSPERMS
    • Topic 9.3
    • Flower structure
    • Pollination
    • Fertilization
    • Germination
  • 2. Flower structure
    • Flowers are reproductive structures
    • They have evolved to send and receive pollen from one flower to another
    • This is the process of pollination
    • Flowers are developed from a series of modified leaves
    • These leaves are arranged in a rings (whorls)
  • 3. Types of pollination
    • Wind
    • Animal
    • Water
    Bumble bee Bombus hortorum on red clover Trifolium pratense Yorkshire fog grass Holcus lanatus
  • 4. Animal pollination
    • Usually insects
    • Also other flying animals
    • e.g. hummingbirds or fruit bats
    Cerambycid beetle pollinating bramble Rubus fruticosus
  • 5. Flower structure Stigma Style Ovary Petal Sepal Filament Anther
  • 6. Pollination
    • Pollen grains contain the male gametes of the plant
    • They are picked up by a pollinator and transferred to another flower
    • Plants tend to specialise in pollinators
    • This ensures the pollen is delivered to same species of plant
    Yellow archangel Lamiastrum galobdolon being pollinated by a bumble bee Bombus hortorum
  • 7. Pollination
    • Most species of flowering plants are hermaphroditic
    • Pollen from a flower could land on the stigma of the same flower or another flower on the same plant = self-pollination
      • Less genetic variation in species
    • Pollen transferred from the anther on one flower to the stigma of another flower on a different plant = cross-pollination
    The honey bee Apis melifera on marsh thistle Cirsium palustris
  • 8. Fertilization
    • Pollination ≠ Fertilization
    • The male gamete (the male nucleus ) has to get to the egg cell
    • The egg cell lies in an ovule in an ovary at the centre of the plant
    • The pollen grain germinates on the stigma
    • It grows a pollen tube down the style
    • It male nuclei travel down the pollen tube to the ovule
  • 9. Fertilization Style Stigma Pollen grain Ovule Embryo sac Pollen tube Ovary
  • 10. Fertilization Egg cell Polar nuclei Embryo sac Micropyle
  • 11. Fertilization Pollen grains of the daisy Bellis perennis
  • 12.  
  • 13. Fruits and seed dispersal Animal dispersal Strawberry Fragaria vesca Wind dispersal Ragwort Senecio Explosive dispersal Bird’s foot trefoil Lotus corniculatus Animal dispersal Wood avens Geum urbanum
  • 14.  
  • 15. Conditions for seed germination
    • Other seeds require more specific conditions:
    • Fire
    • Freezing
    • Passing through digestive system of a seed dispersing animal
    • Washing to remove inhibitors (beans)
    • Erosion of the seed coat (Poppy)
    • Seeds require a combination of certain conditions to germinate:
    • Oxygen for aerobic respiration
    • Water to metabolically activate the cells
    • Temperature for optimal function of enzymes
    • Each seed has its own particular combination of the above three factors
  • 16.
    • Water is absorbed (imbibition)
    • Giberillin (plant growth hormone) is made
    • Giberillin causes enzymes to be made (amylase)
    • Starch is hydrolysed to maltose which can then be absorbed by the young plant
    • Maltose can be further hydrolysed to glucose for cellular respiration or polymerised to form cellulose for the cell walls.
  • 17.