The human life cycle and reproduction

In a nutshell

There are six stages in a human's life cycle. This summary explains what happens from start to finish and the changes that occur along the way.

Life cycle

Definition

A life cycle is a way of describing the sequence of changes that occur in an organism's development.

There are six stages of the human life cycle after an egg is fertilised (1.). These are the foetus (2.), baby (3.), child (4.), adolescent (5.), adult (6.) and old age (7.).

Science; Animals, including humans; KS2 Year 5; The human life cycle and reproduction

Reproduction

Definition

Reproduction is the process by which organisms have babies or offspring. Most animals need a male to provide a sperm cell and a female to provide an egg cell for reproduction to happen. This is called sexual reproduction.

Human male

Science; Animals, including humans; KS2 Year 5; The human life cycle and reproduction — 1. Sperm tube, 2. Penis, 3. Testicles that make sperm.

Human female

Science; Animals, including humans; KS2 Year 5; The human life cycle and reproduction — 1. Ovary (this releases an egg every month), 2. Uterus (womb), 3. Vagina

Stages in the life cycle

Foetus

The foetus is the first stage in the human life cycle. It starts when an egg is fertilised. Fertilisation is when a male's sperm cell joins with a female's egg cell.

1.	An egg cell is released from the ovaries into the mother's womb.
2.	The egg cell is fertilised by a sperm cell from the father. The end product is called a zygote.
3.	The zygote divides into a ball of cells called an embryo and attached itself to the wall of the uterus (womb).
4.	The embryo grows and develops into a foetus.

Baby

At this stage, after nine months of growing, the foetus leaves the womb and enters the world. This marks the change from foetus to baby.

Child

At this stage, humans learn to walk and talk and start to become more independent. This marks the change from baby to child.

Adolescent

At this stage, humans go through puberty. During puberty, the human body changes in response to a substance called hormones. Hormones are a group of chemical messengers that travel in the blood and impact processes like growth and development.

There are various changes that happen to the body during puberty. Some of these are listed below.

Female	Male
Breasts develop.	Hair grows on the face.
Hair grows on the body.	Hair grows on the body.
The ovaries release an egg once a month. If the egg is not fertilised, the lining of the womb will break down and the female will menstruate as blood passes out the vagina. This is known as a period.	The testicles start to produce sperm.

Adult

At this stage, the human body is fully developed and stops growing. This marks the change from teenager or adolescent to adult.

Old age

At this stage, humans begin to slow and shut down. This is the last stage of the lifecycle before death.