Human Reproduction and Puberty, Grade 7
An egg cell survives about 24 hours. Sperm survive for days.
You will find this stated the other way round, with the sperm given two to three days and the ovum given four to five days after ovulation. It is backwards, and it matters, because the fertile period is then worked out from the wrong number.
This page is the Grade 7 human reproduction unit, taught accurately, with the diagrams, the cycle, the correct lifespans and a free worksheet and marking memo.
Where this fits in the curriculum
| Subject | Natural Sciences |
|---|---|
| Grade | 7 |
| Term | 1 |
| Strand | Life and Living |
| Topic | Sexual reproduction, Unit 2: human reproduction |
| Status | Class activities. Nothing in this unit is formally assessed |
| Marks | The topic revision is 20 and covers the plant unit as well. Our worksheet is 40 |
Puberty: what changes, and when
Puberty starts when the pituitary gland signals the reproductive organs to begin producing sex hormones. It is a process over years, not an event, and the ages vary widely between individuals.
| Usually begins | Main physical changes | |
|---|---|---|
| Girls | About 8 to 13 | Growth spurt, breasts develop, hips widen, body hair, periods begin |
| Boys | About 10 to 16 | Growth spurt, voice deepens, body and facial hair, shoulders broaden, muscle develops |
Both also experience emotional changes, including mood swings, because the same hormones act on the brain.
The single most useful thing to say in this lesson is that the ranges overlap and both ends are normal. A learner who starts at 9 and one who starts at 15 are both ordinary, and that sentence does more good than any diagram.
The reproductive organs
| Female | What it does |
|---|---|
| Ovaries | Contain the egg cells and release one about once a month |
| Fallopian tubes | Carry the egg to the uterus. Fertilisation happens here |
| Uterus | Where a fertilised egg implants and the baby develops |
| Cervix | The narrow opening between the uterus and the vagina |
| Vagina | The passage from the cervix to outside the body |
You will see the female system described as having "three main parts": ovaries, uterus and vagina.
Leaving out the Fallopian tubes is a problem, because that is where fertilisation actually happens, and the same diagram usually labels it. A learner asked "where does fertilisation take place?" needs that structure named.
| Male | What it does |
|---|---|
| Testes | Produce sperm cells and the male sex hormone |
| Scrotum | Holds the testes outside the body, where it is slightly cooler |
| Epididymis | Where sperm mature and are stored |
| Sperm ducts | Carry sperm from the testes towards the urethra |
| Prostate and seminal vesicles | Add fluid that feeds the sperm and helps them move |
| Urethra | Carries both urine and semen, but never at the same time |
The scrotum question comes up every year. Sperm production works best a couple of degrees below body temperature, which is why the testes sit outside the body cavity. It is also why tight clothing is linked to lower sperm counts, which is a question the topic itself asks.
The menstrual cycle
| Roughly | What happens |
|---|---|
| Days 1 to 5 | The lining of the uterus breaks down and leaves the body. This is the period |
| Days 6 to 13 | The lining rebuilds and thickens; an egg matures in an ovary |
| About day 14 | Ovulation. An ovary releases one egg into the Fallopian tube |
| Days 15 to 28 | The lining stays thick, ready for a fertilised egg. If none arrives, it breaks down and the cycle restarts |
The 28-day cycle is an average, not a rule. Anything from about 21 to 35 days is normal, and cycles are often irregular for the first year or two after they start.
And the better way to state ovulation is that it happens about 14 days BEFORE the next period, not 14 days after the last one. The second half of the cycle is the fixed part; the first half is what varies. That single reframing is what makes the maths work on cycles that are not 28 days.
How long the cells actually survive
THIS IS THE CORRECTION THE PAGE EXISTS FOR.
What you will read What is true Egg cell "Can still be fertilised four to five days after ovulation" About 12 to 24 hours. One day at most Sperm "Survive two to three days" Up to about five days in the female reproductive tract The two have been swapped. It is the sperm that last for days; the egg is the short-lived one.
And the error does not stay put. The fertile period is then calculated as roughly day 11 to day 18, which puts several fertile days after ovulation. The real fertile window runs the other way: roughly the five days before ovulation plus the day itself, because sperm can already be waiting when the egg arrives.
Fertilisation, implantation and pregnancy
- Sperm travel from the vagina through the cervix and uterus into the Fallopian tubes
- One sperm fuses with the egg. A membrane immediately forms around it so no other sperm can enter
- The fertilised egg, the zygote, divides repeatedly as it travels down the tube
- It implants in the thickened lining of the uterus, usually about a week later
- The placenta develops, connected to the baby by the umbilical cord
- Gestation is about 40 weeks, after which labour begins and the baby is born
Only one sperm fertilises the egg, and that is worth stating plainly because the answer to "how many sperm are needed?" is one.
The placenta does not mix the two bloodstreams, and this is worth getting right.
It brings the mother's blood and the baby's blood very close together so that oxygen and nutrients can pass across to the baby and waste can pass back. The two blood supplies stay separate.
Twins, because someone always asks
| Type | How it happens | Result |
|---|---|---|
| Identical | One egg fertilised by one sperm, then the zygote splits in two | Same sex, same genes |
| Non-identical | Two eggs released, fertilised by two different sperm | May be different sexes; no more alike than any siblings |
This is the answer to the question about two eggs being released at ovulation, and it is a much better use of five minutes than it looks.
Sexually transmitted infections, in one table
| Cause | Examples | Treatment |
|---|---|---|
| Bacteria | Chlamydia, gonorrhoea, syphilis | Curable with antibiotics if treated |
| Viruses | HIV, HPV, herpes | Not cured by antibiotics. HIV is managed with antiretrovirals; HPV is largely preventable by vaccination |
The distinction that matters is bacterial against viral, because it decides whether antibiotics do anything at all. Learners routinely assume every infection is cured by antibiotics, and this is the topic to fix it in.
South African learners are offered the HPV vaccine at school, and this is where that fits: HPV is a virus, the vaccine prevents the infection, and preventing it prevents most cervical cancer.
Teaching it: three things that help
| What | Why |
|---|---|
| Use the correct terms from the first lesson | Vague words make learners embarrassed. Precise ones make it a science lesson |
| Say the ranges overlap and both ends are normal | It is the sentence a 12-year-old actually needs to hear |
| Take written questions anonymously | A box at the door gets the questions nobody will ask out loud, and they are usually the important ones |
One caution on lists of myths. A well-known table in this topic is headed "ten myths" and contains nine. If you set it as a counting exercise, check it first.
How the 40 marks are made up
| Part | Marks |
|---|---|
| Puberty and the changes | 8 |
| The reproductive organs and their functions | 12 |
| The menstrual cycle, and how long the cells survive | 10 |
| Fertilisation, implantation and pregnancy | 6 |
| Sexually transmitted infections | 4 |
Nothing in this unit is formally assessed. The topic revision is 20 marks and covers the plant unit as well. Our worksheet is 40 and the split above is ours.
Free worksheet and marking memo
Both free, no sign up, straight to the PDF.
- Learner worksheet, 40 marks, including both labelled diagrams, the cycle and the cell-survival question
- Marking memorandum, with what to accept for each answer and the five answers that look right and score nothing
Related practicals
- The Biosphere, Grade 7. Reproduction is one of the seven life processes
- Biodiversity and Classification, Grade 7. Which animals lay eggs and which do not, done properly
- Circulatory and Respiratory Systems, Grade 9. The next body system, with a dissection
What you need to teach it
This unit needs no apparatus at all. It needs good diagrams, and a model is worth more than any diagram because a class can take it apart.
| Model | Price | What it shows |
|---|---|---|
| Female pelvis model | R1 150 | The best starting point. The organs in place, in proportion, and in the right order |
| Male pelvis model | R1 290 | The same for the male system |
| Fertilization set of 2 | R1 690 | Fertilisation and early division, enlarged |
| Pregnancy series, 9 models | R3 450 | Development stage by stage. Holds a class better than anything else here |
| Female pelvis section, 2 parts | R2 750 | A cut-through view of the same structures |
If you buy one thing, buy a pelvis model. A diagram on a page is flat and abstract; a model that comes apart in a learner's hands answers the questions they were not going to ask.
An honest note on stock. Several of these are held in ones and twos, and a few lines are currently at zero. Ask us before you plan a purchase order around a set, and we will tell you what we can actually send that week.
The full range is in human anatomy models.