Reproduction and genetics, Year 8: more practice：全部卡片
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- What does an organism that reproduces asexually not need to find, which helps it spread quickly?
A mate
提示Count how many parents it takes.
为什么With 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.
- A new disease attacks one plant in a field of clones. Why is it likely to harm all the others too?
They are genetically identical, so they all share the same weakness
提示Think about how alike clones are inside.
为什么In a varied population some individuals may resist the disease. In clones none has a different gene to help.
- In which organ does a baby develop during pregnancy?
The uterus (womb)
提示It is a muscular, stretchy bag in the lower abdomen.
为什么The uterus has a thick, muscular wall that stretches as the baby grows and pushes the baby out at birth.
- Fertilisation in humans usually happens in the ____, the tube that links the ovary to the uterus.
oviduct
提示It is also called the fallopian tube; it begins with "ovi-".
为什么The egg is released from the ovary into the oviduct. If a sperm reaches it there, fertilisation can happen.
- Why does a wind-pollinated plant make huge amounts of pollen?
Most pollen is wasted, so many grains are needed for a few to reach a stigma
提示Wind blows randomly, so think about the odds of any one reaching a flower.
为什么The wind does not aim, so most grains never land on a stigma. Making a lot raises the chance that some do.
- Pollen from an insect-pollinated flower is often sticky or spiky. How does this help?
It sticks to the insect's body so it is carried to another flower
提示Think about how it catches hold of a visiting bee.
为什么When the insect visits the next flower, some pollen rubs off onto the stigma.
- Pollen moves from the anther of one plant to the stigma of a different plant of the same species. What is this called?
Cross-pollination
提示The pollen crosses from one plant to another.
为什么Cross-pollination mixes genes from two plants, so the seeds produced are more varied.
- After a pollen grain lands on the stigma, how does the male gamete reach the ovule?
Through a pollen tube that grows down the style
提示A thin pathway forms inside the female part, heading for the ovule.
为什么The pollen tube grows down through the style to the ovary and the ovule, where the male gamete fuses with the female gamete.
- After fertilisation, the ovules become seeds. What does the ovary become?
The fruit
提示It surrounds and protects the seeds.
为什么The wall of the ovary swells into the fruit, such as a pea pod or an apple.
- Why is it better for a plant to scatter its seeds away from the parent?
Less competition with the parent and each other for light, water and nutrients
提示Think about what crowded plants would fight over.
为什么Seeds that land far away also help the species spread into new areas.
1★ KS3-BIOL-REP-0057
2★ KS3-BIOL-REP-0058
3★ KS3-BIOL-REP-0059
4★ KS3-BIOL-REP-0060
5★ KS3-BIOL-REP-0061
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8★ KS3-BIOL-REP-0064
9★ KS3-BIOL-REP-0065
10★ KS3-BIOL-REP-0066