16. Reproduction

Asexual reproduction does not involve fusion of gamete nuclei. Rapid reproduction or the absence of a mate may be advantages, but neither alone defines the process.

Flowers, seeds, fertilised eggs and fusion of gamete nuclei indicate sexual reproduction. Do not classify an example from appearance alone: use the reproductive evidence provided.

Genetic uniformity is not always good or always bad. Its effect depends on whether present conditions favour the shared genotype and whether conditions or pathogens change.

Sexual reproduction is defined by fusion of gamete nuclei, not simply by having two organisms present. Self-pollination is still sexual because male and female gamete nuclei fuse.

Pollination, mating and the meeting of whole gamete cells may bring gametes together, but fertilisation specifically names the fusion of their nuclei.

A gamete is haploid; a zygote is diploid. Fertilisation doubles the number relative to one gamete, but restores—not exceeds—the normal diploid number.

Variation is not automatically beneficial in every context. It supports adaptation and breeding, but it also makes offspring less predictable than genetically identical clones.

The stamen is anther plus filament; the carpel includes stigma, style and ovary. An ovule is inside an ovary, not another name for it.

Name the precise structure for the function: pollen is produced by the anther, while the filament only supports it; ovules form seeds, while the ovary forms the fruit.

Do not use large petals, nectar or enclosed reproductive organs as wind-pollination cues; those fit insect pollination.

A pollen grain is classified by a combination of features and how they aid transport, not by one sketch detail alone.

Pollination is transfer, not fusion. Fertilisation happens later, after a pollen tube has grown and nuclei fuse in an ovule.

‘Self’ means the same plant, not only the same flower.

Transfer to another flower on the same plant is self-pollination; transfer between different species is not cross-pollination within this definition.

Self-pollination is still sexual reproduction and can produce some variation; it does not make offspring genetically identical clones.

Pollen landing on the stigma is pollination, not fertilisation; the male nucleus must reach an ovule and fuse with its nucleus.

A feature is an adaptation only when its structure is linked to improved pollen transfer.

Light is not an universal germination requirement. Germination requirements are not the same as the later needs of a growing green plant.

The pollen grain does not itself travel down the style. The pollen tube grows; the pollen nucleus moves through it. Endosperm production and later development are outside this objective.

The sperm duct transports sperm only; the urethra is the shared exit passage for semen and urine.

The ovary produces egg cells, the oviduct is the fertilisation site, and the uterus is the implantation and development site.

Fertilisation is nuclear fusion, not ejaculation, sperm reaching the egg, or implantation in the uterus.

The flagellum moves the cell but does not release energy; mitochondria release energy but do not directly propel it; the acrosome acts at the egg surface.

The egg's energy stores support early development; they do not power active movement. The jelly coat blocks further sperm after one has fertilised the egg.

Only one sperm nucleus normally fertilises one egg; large sperm numbers increase probability, not the number that fuse with the egg.

Implantation is attachment of the embryo to the uterus lining; it is not fertilisation and does not occur in the oviduct.

Maternal and fetal blood normally remain separate. Substances cross the placenta between them; the two blood supplies do not mix directly.

The umbilical vein is named by flow towards the fetal heart, not by oxygen content; here it carries more oxygen than the umbilical arteries.

The placenta keeps maternal and fetal blood separate, but separation does not mean that every harmful substance or pathogen is blocked.

Both hormones occur in all sexes at different concentrations. The syllabus focus is their main roles in developing and regulating secondary sexual characteristics.

Menstruation is shedding of the uterus lining; ovulation is release of an egg from an ovary. They are different events and occur at different times.

The uterus is a target of oestrogen and progesterone, not their production site. FSH and LH are produced by the pituitary gland, not the ovaries.

FSH matures a follicle; LH triggers ovulation. Oestrogen mainly rebuilds the lining before ovulation; progesterone mainly maintains it after ovulation and during pregnancy.

An STI describes a route of transmission, not one specific pathogen type: different STIs can be caused by viruses, bacteria or other pathogens.

HIV is the pathogen; AIDS is a condition that may develop after untreated HIV infection. HIV is not a bacterium and is not killed by antibiotics.

HIV infection and AIDS are not identical: a person can have HIV without having developed AIDS, especially when treatment controls the virus.

HIV is not spread by ordinary social contact, coughing, sneezing or saliva alone. Transmission requires infected body fluids to enter another person's body.

Contraceptive pills prevent pregnancy but do not form a barrier against STIs. Antibiotics may treat susceptible bacterial STIs, but they do not treat HIV or other viral infections.