The learning objectives for this lesson were to understand that evolution involves a change in the allele frequency of a population.
This might happen because of selection pressure on a particular phenotype causing the allele to become more or less prevalent in subsequent generations. An important point to make here is that allele frequencies can be affected by more than just natural selection. Factors such as migration of individuals and birth and death rate can also influence the abundance of an allele in a population.
It is important to understand how phenotype and alleles are linked. Here’s what we learnt in the lesson:
Natural selection operates by selecting against unsuccessful phenotypes – those ones that do not survive to reproductive age or survive but do not successfuly reproduce. Here is a quick recap of natural selection using Darwin’s finches as an example.
If a new mutant allele produces a successful phenotype in an environment then its’ frequency in the population will tend to increase.
A couple of misconceptions that you should avoid:
- natural selection is not a ‘guiding hand’. It does not strive for perfection or direct the evolution of a species in a particular environment. Natural selection merely picks organisms that are ‘fit enough’ to survive to reproduce.
- natural selection isn’t random. It selects strongly for genes that are good enough to allow an organism to reproduce so in that respect it isn’t random. It only selects ‘good’ genes.