Evolution (AQA A Level Biology)

Evolution

• The allele frequencies (within the gene pool) of a population can change over time due to processes such as natural selection

• When the allele frequencies of a population change sufficiently over time, the characteristics of the species will also change

• These changes can become so great that a new species forms

• This process is known as evolution

• Evolution can be defined as:

The formation of new species from pre-existing species over time, as a result of changes to gene pools and allele frequencies from generation to generation

• The formation of new species via the process of evolution has resulted in a great diversity of species on planet Earth

  • Theoretically, at the origin of life on Earth, there would have been just one single species, to begin with

  • This species evolved into separate species (i.e. new species)

  • These species would then have divided again, each forming new species once again

  • Over millions of years, evolution has led to countless numbers of these speciation events, resulting in the millions of species now present on Earth

Evolutionary change over a long period of time has resulted in a great diversity of species

• The evolution of a new species can take a very long time and many generations

• For organisms with a short generation time (such as bacteria), evolution can be observed far more quickly