SL Content Statements

• D3.1.1

  Differences between sexual and asexual reproduction
  

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  Include these relative advantages: asexual reproduction to produce genetically identical offspring by individuals that are adapted to an existing environment, sexual reproduction to produce offspring with new gene combinations and thus variation needed for adaptation to a changed environment.
  

• D3.1.2

  Role of meiosis and fusion of gametes in the sexual life cycle

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  Students should appreciate that meiosis breaks up parental combinations of alleles, and fusion of gametes produces new combinations. Fusion of gametes is also known as fertilization.
  

• D3.1.3

  Differences between male and female sexes in sexual reproduction

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  Include the prime difference that the male gamete travels to the female gamete, so it is smaller, with less food reserves than the egg. From this follow differences in the numbers of gametes and the reproductive strategies of males and females.
  

• D3.1.4

  Anatomy of the human male and female reproductive systems

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  Students should be able to draw diagrams of the male-typical and female-typical systems and annotate them with names of structures and functions.
  

• D3.1.5

  Changes during the ovarian and uterine cycles and their hormonal regulation
  

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  Include the roles of oestradiol, progesterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and both positive and negative feedback. The ovarian and uterine cycles together constitute the menstrual cycle.
  

• D3.1.6

  Fertilization in humans
  

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  Include the fusion of a sperm’s cell membrane with an egg cell membrane, entry to the egg of the sperm nucleus but destruction of the tail and mitochondria. Also include dissolution of nuclear membranes of sperm and egg nuclei and participation of all the condensed chromosomes in a joint mitosis to produce two diploid nuclei.
  

• D3.1.7

  Use of hormones in in vitro fertilization (IVF) treatment
  

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  The normal secretion of hormones is suspended, and artificial doses of hormones induce superovulation.
  

• D3.1.8

  Sexual reproduction in flowering plants
  

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  Include production of gametes inside ovules and pollen grains, pollination, pollen development and fertilization to produce an embryo. Students should understand that reproduction in flowering plants is sexual, even if a plant species is hermaphroditic.
  

• D3.1.9

  Features of an insect-pollinated flower
  

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  Students should draw diagrams annotated with names of structures and their functions.
  

• D3.1.10

  Methods of promoting cross-pollination
  

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  Include different maturation times for pollen and stigma, separate male and female flowers or male and female plants. Also include the role of animals or wind in transferring pollen between plants.
  

• D3.1.11

  Self-incompatibility mechanisms to increase genetic variation within a species
  

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  Students should understand that self-pollination leads to inbreeding, which decreases genetic diversity and vigour. They should also understand that genetic mechanisms in many plant species ensure male and female gametes fusing during fertilization are from different plants.
  

• D3.1.12

  Dispersal and germination of seeds
  

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  Distinguish seed dispersal from pollination. Include the growth and development of the embryo and the mobilization of food reserves.
  

AHL Content Statements

• D3.1.13

  Control of the developmental changes of puberty by gonadotropin-releasing hormone and steroid sex hormones
  

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  Limit to the increased release of gonadotropin-releasing hormone (GnRH) by the hypothalamus in childhood triggering the onset of increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release. Ultimately the increased sex hormone production leads to the changes associated with puberty.
  

• D3.1.14

  Spermatogenesis and oogenesis in humans

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  Include mitosis, cell growth, two divisions of meiosis and differentiation. Students should understand how gametogenesis, in typical male and female bodies, results in different numbers of sperm and eggs, and different amounts of cytoplasm.
  

• D3.1.15

  Mechanisms to prevent polyspermy

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  The acrosome reaction allows a sperm to penetrate the zona pellucida and the cortical reaction prevents other sperm from passing through.
  

• D3.1.16

  Development of a blastocyst and implantation in the endometrium

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  Students are not required to know the names of other stages in embryo development.
  

• D3.1.17

  Pregnancy testing by detection of human chorionic gonadotropin secretion
  

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  Include the production of human chorionic gonadotropin (hCG) in the embryo or developing placenta and the use of monoclonal antibodies that bind to hCG.
  

• D3.1.18

  Role of the placenta in foetal development inside the uterus

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  Students are not required to know details of placental structure apart from the large surface area of the placental villi. Students should understand which exchange processes occur in the placenta and that it allows the foetus to be retained in the uterus to a later stage of development than in mammals that do not develop a placenta.
  

• D3.1.19

  Hormonal control of pregnancy and childbirth

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  Emphasize that the continuity of pregnancy is maintained by progesterone secretion initially from the corpus luteum and then from the placenta, whereas the changes during childbirth are triggered by a decrease in progesterone levels, allowing increases in oxytocin secretion due to positive feedback.
  

• D3.1.20

  Hormone replacement therapy and the risk of coronary heart disease
  

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  NOS: In early epidemiological studies, it was argued that women undergoing hormone replacement therapy (HRT) had reduced incidence of coronary heart disease (CHD) and this was deemed to be a cause- and-effect relationship. Later randomized controlled trials showed that use of HRT led to a small increase in the risk of CHD. The correlation between HRT and decreased incidence of CHD is not actually a cause- and-effect relationship. HRT patients have a higher socioeconomic status, and this status has a causal relationship with lower risk of CHD.