Evolution by Natural Selection
Biology: Cambridge International A Level, topic 17.3.1
Principles of Natural Selection
Natural selection is the process that leads to evolution in a population. In order to understand how this process functions, it is important to learn the key principles of natural selection.
Random mutation
- Mutations are changes in the gene sequence of DNA.
- Random mutations can arise spontaneously.
- New mutations can result in new alleles of a gene.
Variation in mutations
- Most mutations are harmful because they alter the normal functioning of a gene.
- But by chance, some mutations might confer a beneficial trait.
- An individual with a beneficial mutation will be more likely to survive and reproduce than an individual without the mutation.
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Inheritance
- When an individual reproduces, their offspring will inherit half of their genes.
- When an individual with an advantageous mutation reproduces, the allele is inherited by their offspring.
Change in allele frequency
- Individuals in the next generation who have the advantageous mutation are also more likely to reproduce and pass on the allele.
- Over many generations, the new allele will increase in frequency in the population.
- The change in allele frequency over time is called evolution.
Test yourself on Evolution by Natural Selection
Which of the following statements about natural selection are true?
What is the definition of evolution?