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Changing the characteristics of a species
The characteristics of a species can be changed by:
- natural selection
- selective breeding
- genetic engineering.
The table shows some differences between these.
| Natural selection | Selective breeding | Genetic engineering | |
|---|---|---|---|
| Number of generations needed for change | very many | many | one |
| Human intervention | not needed | needed | needed |
| Desired outcome known? | no | yes | yes |
| New species formed? | yes | no | no |
| Notes | This is the mechanism of change in Darwin's theory of evolution | This is how new varieties or breeds are usually produced | Genetic information can come from the same species or from a different one |
In selective breeding and genetic engineering, there is a goal or desired outcome. For example, we may wish to produce a variety of cow capable of producing a lot of milk, or a bacterium capable of producing insulin [insulin: A hormone that regulates the level of sugar in the blood. It is produced in the Islets of Langerhans, in the Pancreas. ].
There is no goal in natural selection: although we find that particular species are well adapted to their environments, natural selection does not 'know' what the species should be like. Individuals that are better suited to their environment are more likely to survive to reproduce, and so pass on their characteristics to the next generation, than those that are poorly suited.
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