Flashcards · 0610 · Topic 16

Reproduction flashcards

27 cards on Topic 16, subtopics 16.1 to 16.6. Pick a subtopic or study them all.

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Asexual reproduction: A process resulting in the production of genetically identical offspring from one parent.
Asexual reproduction: gametes, speed and variation: No gametes or fertilisation; fast; offspring are genetically identical, so there is no variation.
Advantages and disadvantages of asexual reproduction in a cropExtended: For: uniform, predictable plants with the grower's chosen features, produced quickly. Against: genetically identical plants can all be destroyed by one disease, and no new varieties arise.

Sexual reproduction: A process involving the fusion of the nuclei of two gametes to form a zygote, and the production of offspring that are genetically different from each other.
Fertilisation: The fusion of the nuclei of gametes.
Gamete and zygote nuclei: haploid or diploid?Extended: Gamete nuclei are haploid; the zygote nucleus is diploid.
Advantage of sexual reproduction for a wild populationExtended: Offspring vary, so the population can adapt when the environment changes. (Asexual reproduction is faster and needs no mate.)

Functions of the anther, stigma and ovary: Anther: makes pollen. Stigma: receives pollen. Ovary: contains the ovules, which contain the female gametes.
Pollination: The transfer of pollen grains from an anther to a stigma.
Insect-pollinated vs wind-pollinated flowers: Insect: large bright scented petals; anthers and sticky stigma inside; fewer, larger sticky or spiky pollen grains. Wind: small dull petals; anthers and feathery stigmas hang outside; huge numbers of small light smooth grains.
Conditions needed for germination: Water, oxygen and a suitable temperature. (Not light.)
Self-pollination vs cross-pollinationExtended: Self: pollen to the stigma of the same flower or another flower on the same plant. Cross: pollen to a flower on a different plant of the same species. Cross-pollination gives more variation but relies more on pollinators.
Events from pollination to fertilisation in a flowering plantExtended: Pollen lands on the stigma; a pollen tube grows down through the style and enters the ovule through the micropyle; the pollen nucleus fuses with the nucleus in the ovule.

Functions of the testes, sperm ducts, prostate gland and urethra: Testes: make sperm. Sperm ducts: carry sperm to the urethra. Prostate gland: adds fluid for sperm to swim in. Urethra: carries semen out through the penis.
Functions of the ovaries, oviducts, uterus and cervix: Ovaries: make eggs. Oviducts: carry the egg; site of fertilisation. Uterus: site of implantation, where the fetus develops. Cervix: holds the fetus in and widens at birth.
Sperm vs egg cell: Sperm: much smaller, motile, made in very large numbers; flagellum, many mitochondria, acrosome with enzymes. Egg: much larger, not motile, few made; energy stores in the cytoplasm and a jelly coat.
Placenta, umbilical cord and amniotic fluid: Placenta: exchange of substances between mother and fetus. Umbilical cord: links the fetus to the placenta. Amniotic fluid (in the amniotic sac): protects and cushions the fetus.
What crosses the placenta, and in which direction?Extended: Mother → fetus: oxygen, glucose, amino acids and other dissolved nutrients. Fetus → mother: carbon dioxide and urea. Some pathogens and toxins can also cross. The bloods do not mix.

Roles of testosterone and oestrogen at puberty: Testosterone (testes): facial and body hair, deeper voice, muscle growth. Oestrogen (ovaries): breasts develop, hips widen, menstrual cycle starts.
Menstrual cycle: changes in the ovary: Days 1–5: a new follicle starts to develop. Days 6–13: the egg matures in the follicle. About day 14: ovulation, the egg is released.
Menstrual cycle: changes in the uterus lining: Days 1–5: the lining breaks down and is lost. It then repairs and thickens, and is kept thick after ovulation ready for implantation. If no implantation, it is lost again.
FSH and LH: source and rolesExtended: Both from the pituitary gland. FSH: a follicle develops and oestrogen is made. LH: triggers ovulation and formation of the corpus luteum.
Progesterone: source and roleExtended: From the corpus luteum (and the placenta in pregnancy). Maintains the uterus lining and inhibits FSH and LH. A fall in progesterone leads to menstruation.

Sexually transmitted infection (STI): An infection that is transmitted through sexual contact.
HIV and AIDS: HIV is a pathogen that causes an STI. HIV infection may lead to AIDS.
Ways HIV is transmitted: Unprotected sex; sharing needles; transfusion of infected blood; from mother to baby across the placenta, at birth or in breast milk.
Ways to control the spread of STIs: Condoms; fewer sexual partners; testing, treating and informing partners; screening donated blood; not sharing needles; education.