Reproduction and genetics, Year 8: more practice

A mate

HintCount how many parents it takes.

The whyWith only one parent and no gametes to join, an organism such as a bacterium or a strawberry plant never has to search for a mate, so it can spread fast.

They are genetically identical, so they all share the same weakness

HintThink about how alike clones are inside.

The whyIn a varied population some individuals may resist the disease. In clones none has a different gene to help.

The uterus (womb)

HintIt is a muscular, stretchy bag in the lower abdomen.

The whyThe uterus has a thick, muscular wall that stretches as the baby grows and pushes the baby out at birth.

oviduct

HintIt is also called the fallopian tube; it begins with "ovi-".

The whyThe egg is released from the ovary into the oviduct. If a sperm reaches it there, fertilisation can happen.

Most pollen is wasted, so many grains are needed for a few to reach a stigma

HintWind blows randomly, so think about the odds of any one reaching a flower.

The whyThe wind does not aim, so most grains never land on a stigma. Making a lot raises the chance that some do.

It sticks to the insect's body so it is carried to another flower

HintThink about how it catches hold of a visiting bee.

The whyWhen the insect visits the next flower, some pollen rubs off onto the stigma.

Cross-pollination

HintThe pollen crosses from one plant to another.

The whyCross-pollination mixes genes from two plants, so the seeds produced are more varied.

Through a pollen tube that grows down the style

HintA thin pathway forms inside the female part, heading for the ovule.

The whyThe pollen tube grows down through the style to the ovary and the ovule, where the male gamete fuses with the female gamete.

The fruit

HintIt surrounds and protects the seeds.

The whyThe wall of the ovary swells into the fruit, such as a pea pod or an apple.

Less competition with the parent and each other for light, water and nutrients

HintThink about what crowded plants would fight over.

The whySeeds that land far away also help the species spread into new areas.