Reproduction and genetics, Year 7: more practice

testosterone

提示It begins with "testo-", like the organ that makes it.

为什么Testosterone causes a boy's voice to deepen, his body hair to grow and his testes to start making sperm.

Oestrogen

提示It begins with "oe-".

为什么Oestrogen also helps control the menstrual cycle once periods have begun.

A growth spurt

提示Think of a sudden short burst of speed.

为什么Growth spurts happen at different ages for different people, so friends can differ a lot in height for a while.

Mood swings

提示Feelings that rise and fall like a playground ride.

为什么Mood swings are a normal emotional change in puberty. Talking to someone you trust can help.

The stigma

提示Pollen has to stick here for the next stage to happen.

为什么The stigma sits at the top of the style. Its sticky surface catches pollen grains.

The carpel

提示The stamen has the anther. The female part holds the ovary.

为什么The carpel is made of the stigma, the style and the ovary. The stamen is made of the anther and its filament.

Ovules

提示Each one can become a seed after fertilisation.

为什么An ovule contains the female gamete. After fertilisation the ovule grows into a seed.

The offspring grow up and reproduce, so the cycle starts again

提示What does the new generation do when it grows up?

为什么Each generation produces the next, so the stages repeat over and over.

The pupa (chrysalis)

提示The caterpillar stays still inside a case while its body is rebuilt.

为什么The order is egg, caterpillar (larva), pupa, adult butterfly.

A tadpole

提示It hatches from frogspawn.

为什么The order is egg (spawn), tadpole, young frog, adult frog. The tadpole grows legs and lungs as it changes.