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Leaving certificate biology
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Unit 1Ecology theory5 Topics|1 Quiz
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Nutrient recycling4 Topics|1 Quiz
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Ecological relationships and population dynamics2 Topics
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Human impact on the ecosystem2 Topics
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Study of a grassland ecosystem3 Topics
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Responses in the Flowering Plant4 Topics|1 Quiz
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Unit 3Sexual reproduction in the flowering plant1 Topic
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The human reproductive system3 Topics
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The menstrual cycle2 Topics
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Pregnancy2 Topics
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The circulatory system4 Topics
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Blood5 Topics
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The heart5 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
