Biology · Rung 4 of 9

Reproduction and sexuality

Ovulation is the release of an egg, around the middle of the cycle, and that “around” is enormous: cycles vary from month to month, so counting days is unreliable. Fertilisation happens in the tube, not the womb, and the embryo takes days to travel down and implant: two moments nearly a week apart. In contraception there is a costly and widespread confusion: hormonal methods are highly effective against pregnancy and protect against no infection at all. Only the condom does both, because it is the only one that puts up a barrier. Many sexually transmitted infections give no symptoms for months, so feeling fine tells you nothing; a test does. And consent is decided each time and can be withdrawn at any moment: it is not inferred from silence or from an earlier yes.

Where this sits

This is where the ladder starts: nothing is needed before it.

Exercises from this rung

Generated by the app, from easiest to hardest

  1. Which method prevents both pregnancy and sexually transmitted infections?

    • The condom
    • The hormonal implant
    • The contraceptive pill
    • The intrauterine device

    Why Only the condom, because it is the only one that puts up a barrier. Hormonal methods are highly effective against pregnancy and **protect against no infection at all**, which is the most widespread and most costly confusion. Many sexually transmitted infections give no symptoms for months, so feeling fine tells you nothing: a test does.

    easier

  2. What sets puberty off?

    • That the hormones of childhood run out
    • That the body reaches a particular weight and height
    • That the bones finish growing altogether
    • That the brain starts sending a hormone which wakes the gonads

    Why The order comes from the brain, not the body: a patch of the hypothalamus starts releasing pulses of a hormone that wakes the ovaries or testes, and those release theirs. That is why puberty arrives at no fixed age and in no fixed order, and why it can come years early or late with nothing wrong.

    in between

  3. Where does fertilisation normally happen?

    • In the tube, before reaching the womb
    • In the cervix
    • In the womb, already implanted
    • In the ovary, as the egg leaves

    Why In the Fallopian tube. The egg is fertilised there and travels down to the womb over several days, dividing on the way, and only then implants. That distinction matters: fertilisation and implantation are two moments nearly a week apart, and a fair number of fertilisations never implant at all.

    harder