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Leaving certificate biology

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  1. Ecology theory
    5 Topics
    |
    1 Quiz
  2. Unit 1
    Nutrient recycling
    4 Topics
    |
    1 Quiz
  3. Ecological relationships and population dynamics
    2 Topics
  4. Human impact on the ecosystem
    2 Topics
  5. Study of a grassland ecosystem
    3 Topics
  6. Responses in the Flowering Plant
    4 Topics
    |
    1 Quiz
  7. Unit 3
    Sexual reproduction in the flowering plant
    1 Topic
  8. The human reproductive system
    3 Topics
  9. The menstrual cycle
    2 Topics
  10. Pregnancy
    2 Topics
  11. The circulatory system
    4 Topics
  12. Blood
    5 Topics
  13. The heart
    5 Topics
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Insect pollinated flowers

Wind pollinated flowers

Development of pollen

  • Diploid (microspore) mother cell divides by meiosis producing four haploid cells

  • Each of these cells divide by mitosis forming a pollen grain with two haploid nuclei

  • The generative nucleus and the tube nucleus

Development of the embryo sac

  • Diploid megaspore mother cell divides by meiosis giving four haploid daughter cells

  • Only one survives

  • This becomes the embryo sac

  • The embryo sac divides by mitosis to give eight haploid nuclei

  • Two of the haploid nuclei become the polar nuclei

  • One haploid nucleus becomes the egg cell

What is pollination ?

  • Pollination is the transfer of pollen from anther to stigma

Self - pollination

  • Pollen grains are transferred onto the stigma of the same flower

Cross - pollination

  • Pollen grains are transferred onto the stigma of a flower on another plant of the same species

  • it is carried out by insects and wind

Fertilization

  • Nitrifying bacteria in the soil convert ammonium salts into nitrites and then onto nitrates
  • These nitrates ate absorbed by plants to make protein