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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
Lesson 10, Topic 2
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Development of the embryo

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Development of the embryo

  • The zygote divides by mitosis

  • About 3 days after fertilization it forms a ball of cells called a morula

  • Around day 5, a hollow ball of cells called the blastocyst forms

  • The outer cells of the blastocyct (trophoblast) will later form the membranes around the embryo

  • The inner cells will form the embryo

  • The blastocyst is pushed down the Fallopian tube by the movement of cilia

  • implantation is the burrowing of the blastocyst into the lining of the uterus

  • Implantation normally takes place on day 7 after fertilization

  • At this stage pregnancy is said to have started

The three germ layers

  • Each of the 3 layers gives rise to different structures in the embryo