Sexual & Asexual Reproduction: Differences (Edexcel IGCSE Science (Double Award))
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Sexual Reproduction
Sexual reproduction is:
The process involving the fusion of the nuclei of two gametes to form a zygote (fertilised egg cell) and the production of offspring that are genetically different from each other
Two parent organisms are required for sexual reproduction
The gametes are produced through meiosis
After fertilisation, the offspring develops through mitotic cell divisions
Offspring produced by sexual reproduction are genetically different to the parent organisms
They share half of the DNA from each parent
Sexual reproduction is a relatively slow reproduction process
Variation introduced into populations as a result of sexual reproduction, provides a survival advantage to the population
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Asexual Reproduction
Asexual reproduction is:
The process resulting in genetically identical offspring being produced from one parent
Asexual reproduction does not involve gametes or fertilisation
Only one parent is required so there is no fusion of gametes and no mixing of genetic information
As a result, the offspring are genetically identical to the parent and to each other (they are clones)
The process occurs much more quickly and efficiently than sexual reproduction which can provide a survival advantage to populations
However, lack of genetic variation means that populations are more vulnerable to disease or environmental change
Many plants reproduce via asexual reproduction
Bacteria produce exact genetic copies of themselves in a type of asexual reproduction called binary fission
Bacteria produce exact genetic copies of themselves in a type of asexual reproduction called binary fission
Comparing Sexual & Asexual Reproduction
The key differences between sexual and asexual reproduction are compared in this table below:
Feature | Asexual Reproduction | Sexual Reproduction |
|---|---|---|
Number of parent organisms | One | Two |
Type of cell division required to produce offspring | Mitosis | Meiosis (to produce gametes) Mitosis after fertlisation |
Level of genetic similarity between offspring | Genetically identical to each other (and to the parent) | Genetically unique (and genetically different from both parents) |
Sources of genetic variation in offspring | Only one source: mutation | Three sources:
|
Number of offspring produced | Usually relatively large numbers | Usually relatively limited numbers |
Time taken to produce offspring | Usually relatively fast | Usually relatively slow |
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