Reproduction

Human reproduction

Human reproduction is the making of sperm and egg, their meeting, and the support of an embryo inside the uterus.

CAPS

Grade 12 · Life Sciences · Reproduction

Life Sciences is two papers. Use the strand to know which one.

  • Where it is examined

    Paper 1 is reproduction, responding to the environment, and homeostasis. Paper 2 is DNA, meiosis, genetics and evolution. Each paper is 150 marks.

  • How to write it

    Name the structure, then say what it does. A labelled diagram only scores if the labels are the biological names. “It helps the body” is not a function.

  • How a marker reads it

    A common mix-up is to say fertilisation happens in the uterus, or that menstruation means an egg is released that day.

A 2-mark “explain” wants two facts, or one fact and its reason. Extra sentences that contradict the first one can cancel a mark.

cycle

Diagram

Worked theory

Worked theory. Day 1 of a cycle is the start of menstruation. Oestrogen rebuilds the lining. A surge of LH releases the egg. If sperm are in the oviduct then, one nucleus joins the egg’s nucleus. The ball of cells reaches the uterus and implants. Progesterone keeps that lining. If no embryo implants, progesterone falls and the lining is shed again. The sperm’s tail is for swimming. The egg’s food store supports the first divisions. Neither cell is a baby yet. Implantation, not the moment of ejaculation, is the start of a pregnancy in the uterus.

More worked examples

  • Dates in one cycle

    Call day 1 the first day of menstruation. Ovulation is around day 14, when LH peaks. Sperm meet the egg in the oviduct, not in the uterus. If they meet on day 15, the zygote takes about a week to become a blastocyst and implant in the lining, around day 21. No implantation, and progesterone falls, and day 1 comes again near day 28. A pregnancy test before implantation is reading a lining that does not yet hold an embryo.

  • A condom and the oviduct

    Sperm are deposited in the vagina and must swim through the uterus to the oviduct, which is where a sperm meets an egg. A condom worn for the whole act stops sperm entering the vagina, so the oviduct never receives them. The pill’s idea is different: it prevents ovulation, so there is no egg to meet. One method blocks the path. The other removes the egg. A method that is put on after ejaculation has missed the path.

In ordinary words

Testes make sperm and testosterone. Ovaries make eggs and the hormones oestrogen and progesterone. In a typical 28-day cycle, menstruation sheds the uterus lining, an egg is released about midway, and the lining is ready for an embryo. Fertilisation usually happens in the oviduct, not in the uterus. The zygote divides and becomes a blastocyst that implants in the lining. The placenta is the exchange surface between mother and embryo. It is not a filter that blocks every harmful substance.

In South Africa

The cycle you graph in Grade 12 is this story, told as hormone levels over 28 days.

Part 1 / 4

What it is

Human reproduction is the making of sperm and egg, their meeting, and the support of an embryo inside the uterus.

Diagram
Diagram

More worked examples

Board walkthroughs on this topic. Open one, copy the working, then try the next.

Example 1 / 20

A woman's cycle is 28 days and menstruation starts on day 1. On which day is ovulation likely, and which hormone surge triggers it?

How we got there

Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.

Explain in another language · 11

1. What is the question asking?

Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: A woman's cycle is 28 days and menstruation starts on day 1. On which day is ovulation likely, and which hormone surge triggers it?

In other words — as if you have never seen this before

If you have never seen this before: Ovulation ≈ day 14. We will name a method in words, write the formula with no numbers, then substitute one line at a time.

2. What do we already know?

28-day cycle.

3. Which method — and why this one?

Ovulation ≈ day 14.

4. Step-by-step working

  1. 01 / 07

    Step A — Read the question twice

    Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.

    Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.

  2. 02 / 07

    Step B — Write the given in a column

    28-day cycle.

    Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.

  3. 03 / 07

    Step C — Name the method in words

    Ovulation ≈ day 14.

    Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.

  4. 04 / 07

    Identify the given

    Ovulation about day 14, triggered by a surge of LH from the pituitary.

    Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.

  5. 05 / 07

    Step G — Sense-check the size

    Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.

    Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.

  6. 06 / 07

    Step F — Box the answer with its unit

    Day 14; LH surge.

    Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.

  7. 07 / 07

    Step H — What the marker is looking for

    On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.

    Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.

5. The answer

Day 14; LH surge.

Copy onto your answer sheet — in this order

Answer: Day 14; LH surge.

6. Check it like a marker

The fertile window is a few days around ovulation.

7. A trap first-timers fall into

First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”

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