D3.1 Reproduction Flashcards
D3.1.1—Differences between sexual and asexual reproduction
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
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
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
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
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
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
The normal secretion of hormones is suspended, and artificial doses of hormones induce superovulation
D3.1.8—Sexual reproduction in flowering plants
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
Students should draw diagrams annotated with names of structures and their functions.
D3.1.10—Methods of promoting cross-pollination
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
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
Distinguish seed dispersal from pollination. Include the growth and development of the embryo and the
mobilization of food reserves.
D3.1.13—Control of the developmental changes of puberty by gonadotropin-releasing hormone and
steroid sex hormones
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
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
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
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
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
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
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
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 causeand-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 causeand-effect relationship. HRT patients have a higher socioeconomic status, and this status has a causal
relationship with lower risk of CHD.
