ReproductionEdexcel GCSE Biology: Revision notes
Section 1
What Is Asexual Reproduction?
One parent, no fusion of gametes, offspring genetically identical (clones).
Advantages: no need to find a mate, rapid reproductive cycle. Disadvantages: no variation, whole population vulnerable to same threats.
Always explain WHY no variation is a disadvantage, e.g. vulnerability to disease.
Section 2
What Is Sexual Reproduction?
Fusion of male and female gametes (fertilisation) from two parents, producing genetically different offspring.
Advantages: variation, aids survival if conditions change. Disadvantages: requires finding a mate, slower.
Section 3
Comparing Asexual and Sexual Reproduction
| Feature | Asexual | Sexual |
|---|---|---|
| Parents | 1 | 2 |
| Variation | None | Present |
| Mate needed | No | Yes |
| Speed | Rapid | Slower |
Use exact wording: 'genetically identical' vs 'genetic variation'.
Section 4
How Does Meiosis Produce Gametes?
Meiosis occurs in testes/ovaries: cell copies DNA, divides twice into four daughter cells, each with half the chromosome number (haploid), each genetically different.
Do not confuse with mitosis (2 identical diploid cells).
46 chromosomes → 23 in each of 4 gametes.
Must Know
- Asexual: 1 parent, no variation, no mate needed, rapid.
- Sexual: 2 parents, variation, mate needed, slower.
- Meiosis: 4 haploid daughter cells, genetically different.
That's the notes covered.
Carry on to the next subtopic.