Topics · Primary Science · Cycles: Human Reproduction
Human reproduction and growth
A new human begins when a sperm joins an egg. The baby then develops inside the mother, is born, and grows through recognised stages — and papers ask for the stages and the words in the right order.
- 214 exam papers analysed
- appears in 71% of P6 Science papers
- ~3 min read
01 How a new life begins
The mother produces an egg; the father produces sperm.
Fertilisation is the moment one sperm joins one egg. The cell that results is called a zygote, and it grows into a baby.
Fertilisation happens inside the mother's body, which is called internal fertilisation. Fish and frogs fertilise externally, in water, and papers use that contrast.
Only one sperm fertilises the egg, and it needs both an egg and a sperm — neither on its own can produce a new human.
02 Developing before birth
The baby grows in the womb for about nine months.
It cannot eat or breathe for itself, so it receives everything through the umbilical cord: oxygen and food come in, and waste is carried away.
This is why what the mother takes in matters — anything in her blood can reach the baby.
Birth is the baby leaving the mother's body, after which it breathes and feeds for itself.
03 The stages of growth
After birth, humans pass through recognised stages. Papers ask for them in order.
- Baby — completely dependent, growing very fast.
- Child — walking, talking, learning; growth continues steadily.
- Adolescent — the body changes and becomes able to reproduce. This stage is called puberty.
- Adult — fully grown and able to reproduce, which returns the cycle to its start.
04 Comparing with other animals
Humans and most mammals give birth to live young and feed them on milk. The young develop inside the mother, so relatively few are produced and most survive.
Fish and frogs lay many eggs and fertilise them outside the body, in water. Most of those eggs are eaten or never develop, which is why so many are laid.
That trade is a favourite question: few young with lots of care, or many young with none. Both work; they are different strategies for the same problem.
05 How to say them
These are words most children have never said out loud, and a word you cannot say is a word you avoid using. Capitals mark the syllable you lean on. Tap the speaker to hear it.
- fertilisationsayfur-ti-ly-ZAY-shuhn
The joining of a sperm and an egg, which starts a new life.
- sperm
The reproductive cell produced by the father.
- eggmore than oneeggs
The reproductive cell produced by the mother.
- wombsaywoom
The organ inside the mother where the baby develops before birth.
- umbilical cordsayum-BIL-i-kuhl
The cord carrying food and oxygen to the baby and waste away from it.
- pubertysayPYOO-buh-tee
The stage when the body changes and becomes able to reproduce.
- adolescentsayad-uh-LESS-uhntmore than oneadolescents
A young person between child and adult, going through puberty.
06 What each level is tested on
The same topic, asked differently as it goes up. The percentage is the share of papers at that level in which it appears.
- P5
Fertilisation, development in the womb, and the stages of human growth.
Practise P5 Cycles: Human Reproduction — 10 questions →63% of P5 papers
- P6
Comparing human reproduction with other animals, and reproduction inside longer questions.
Practise P6 Cycles: Human Reproduction — 9 questions →71% of P6 papers
07 Mistakes worth knowing about
Each of these is wrong. Decide why before you open it.
“The baby breathes through its mouth in the womb.”
It receives oxygen through the umbilical cord. It does not breathe until it is born.
“Fertilisation is when the baby is born.”
Fertilisation is when the sperm joins the egg, about nine months before birth.
“Humans reproduce like fish.”
Human fertilisation is internal and the young develop inside the mother. Fish fertilise externally in water and lay many eggs.
“Many sperm fertilise the egg.”
Only one joins it. Many are produced, but a single sperm and a single egg make one zygote.
“Fish lay lots of eggs because they are bad parents.”
It is a different strategy: many young with no care, against few young with a great deal of it. Most of those eggs do not survive.
Now try it
19 questions across 2 levels, marked as you go with the working shown.