Sexual reproduction
Two parents, varied young
- Sexual reproduction needs two parents.
- The nuclei of two gametes (sex cells) fuse to make a zygote.
- This joining is called fertilisation.
Practice
Fertilisation is:
Fertilisation joins (fuses) the nuclei of a male and a female gamete, forming a zygote.
Variation
- The offspring get a mix of genes from both parents, so they show variation (they are genetically different).
- Advantage: variation means some offspring may survive if the environment changes.
- Disadvantage: it is slower and needs two parents.
- (Supplement) Gamete nuclei are haploid (one set of chromosomes); the zygote is diploid (two sets).
Practice
Why do offspring from sexual reproduction show variation?
A mix of genes from both parents makes the offspring genetically different — this variation helps survival if conditions change.
Practice
Gamete nuclei are haploid and the zygote nucleus is diploid.
Each gamete carries one set of chromosomes (haploid); when they fuse, the zygote has two sets (diploid).
You've got it
Key idea
- sexual reproduction = two parents; gamete nuclei fuse at fertilisation → zygote
- offspring show variation (a mix of genes) → some may survive change
- (Supplement) gametes haploid, zygote diploid