11.4 Sexual reproduction

Essential idea: Sexual reproduction involves the development and fusion of haploid gametes.

Understandings, applications and skills

11.4.U1	Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis and differentiation.
11.4.U2	Processes in spermatogenesis and oogenesis result in different numbers of gametes with different amounts of cytoplasm.
11.4.U3	Fertilization in animals can be internal or external.
11.4.U4	Fertilization involves mechanisms that prevent polyspermy. [Fertilization involves the acrosome reaction, fusion of the plasma membrane of the egg and sperm and the cortical reaction.]
11.4.U5	Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy.
11.4.U6	HCG stimulates the ovary to secrete progesterone during early pregnancy.
11.4.U7	The placenta facilitates the exchange of materials between the mother and fetus.
11.4.U8	Estrogen and progesterone are secreted by the placenta once it has formed.
11.4.U9	Birth is mediated by positive feedback involving estrogen and oxytocin.
11.4.A1	The average 38-week pregnancy in humans can be positioned on a graph showing the correlation between animal size and the development of the young at birth for other mammals.
11.4.S1	Annotation of diagrams of seminiferous tubule and ovary to show the stages of gametogenesis.
11.4.S2	Annotation of diagrams of mature sperm and egg to indicate functions.

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Vocabulary

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Quick quiz

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Nature of science

Assessing risks and benefits associated with scientific research—the risks to human male fertility were not adequately assessed before steroids related to progesterone and estrogen were released into the environment as a result of the use of the female contraceptive pill. (4.8)