Sexual reproduction
Introduced| English | Meaning |
|---|---|
| sexual reproduction/ˈsekʃuːəl rɪprəˈdʌkʃn/ | Reproduction involving the fusion of male and female gametes, giving genetic variety. |
| gametes/ˈɡæmiːts/ | Haploid reproductive cells that fuse during fertilisation to form a zygote. |
| chromosomes/ˈkrəʊməsəʊmz/ | Structures made of DNA and associated proteins that carry genetic information. |
| fertilisation/ˌfɜːtɪlaɪˈzeɪʃn/ | The fusion of the nuclei of two gametes to form a zygote. |
| zygote/ˈzaɪɡəʊt/ | The single cell formed when two gametes fuse, which divides to become an embryo. |
| variation/ˌveərɪˈeɪʃn/ | Differences in characteristics between individuals or values within a set. |
Mixing two parents
- Most animals and many plants reproduce using two parents.
- This sexual reproduction 有性生殖 mixes genes, creating offspring that are all different.
Gametes are:
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Gametes carry half the chromosomes.
Each gamete carries ______ the normal number of chromosomes.
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Fertilisation restores the full number.
Gametes 配子
- Sexual reproduction involves gametes (sex cells): a male gamete and a female gamete.
- Each gamete has half the normal number of chromosomes 染色体.
The sperm is small and swims; the egg cell is large and stores food
Sexual reproduction
Two parents each contribute a gamete; fertilisation combines them, creating variation.
Fertilisation is the:
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Two gametes fuse to form a zygote.
The cell formed when two gametes fuse is called a zygote.
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The zygote grows into a new organism.
Fertilisation 受精
- Fertilisation is the fusion of a male and female gamete.
- This restores the full chromosome number and forms a zygote 合子, which grows into a new organism.
A key advantage of sexual reproduction is that it produces:
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Mixing two parents' genes creates variation.
Variation 变异
- Because offspring get genes from two parents, they show variation.
- This variation is the raw material for evolution and helps populations survive change.
Worked example. A sperm (23 chromosomes) fuses with an egg (23 chromosomes) at fertilisation, making a zygote with the full 46. The mix of two parents' genes makes each child unique.
You've got it
- sexual reproduction uses two parents and gametes (with half the chromosomes)
- fertilisation = fusion of male and female gametes → a zygote
- it produces variation, helping populations adapt and survive