11.4
sexual reproduction
Essential Idea: Sexual reproduction involves the development and fusion of haploid gametes.
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Nature of Science: Assessing risks and benefits with scientific research: the risks to human male fertility were not adequately assessed before steroids related to progesterone and oestrogen were released into the environment as a result of the use of the female contraceptive pill.
UNDERSTANDINGS:
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11.4.U1 Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis, and differentiation.
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11.4.U2 Processes in spermatogenesis and oogenesis result in different numbers of gametes with different amounts of cytoplasm.
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11.4.U3 Fertilization in animals can be internal or external.
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11.4.U4 Fertilization involves mechanisms that prevent polyspermy.
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11.4.U5 Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy.
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11.4.U6 HCG stimulates the ovary to secrete progesterone during early pregnancy.
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11.4.U7 The placenta facilitates the exchange of materials between the mother and foetus.
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11.4.U8 Oestrogen and progesterone are secreted by the placenta once it has formed.
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11.4.U9 Birth is mediated by positive feedback involving oestrogen and oxytocin.
APPLICATIONS & SKILLS:
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Application: The average 38-week pregnancy in humans can be positioned on a graph showing the correlation between animal size and the development stage of the young at birth for other mammals.
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Skill: Annotation of diagrams of seminiferous tubule and ovary to show the stages of gametogenesis.
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Skill: Annotation of diagrams of mature sperm and egg to indicate functions.
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RESOURCES:
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