What is a gene pool?
The complete set of unique alleles of genes in a population
What is the gene frequency?
The frequency of occurence of an allele in relation to that of other alleles of he same gene in a population
In large populations with random mating the gene frequency remains fairly stable. This is called...?
Through what ways can the gene frequency be changed?
- Mutations - new alleles are added to the gene pool
- Natural selection - a change in the environment can all of a sudden favour other alleles (eg the Peppered Moth)
- Gene migration - new alleles are introduced by immigrants from a different gene pool
- Non-random mating - inbreeding (which leads to an increased number of homozygous individuals with recessive traits)
- Genetic drift - a few individuals from a popluation become isolated. They do not have the complete range of alleles and after several generations, the gene frequency of the isolated group becomes distinctive from the original population
What is a species?
A group of organisms that share common anatomical and physiological characteristics. They are able to interbreed and produce fertile offspring
What is speciation?
The formation of a new species
- Large population of freeely interbreeding organisms
- A barrier cuts the popluation in half. No breeding (gene exchange) takes place between the two.
- Over time the two sub-populations change through natural selection and mutations
- After a while their gene pools totally change and evern if the barrier is removed, the two populations cannot interbreed and have become two different species
What are the three types of barriers?
- Geographical - eg mountains, desert, seas
- Ecological - changes in temperature, pH, moisture
- Reproductive - mating at different times of the year, become sexually non-compatible