| Genetic diversity meaning | - The no. of different alleles of genes in a species or population
- Allows natural selection to occur |
| What increases genetic diversity | - Mutations in DNA, forming new alleles
- Different alleles being introduced into a population from another migrating population + reproduce, called gene flow |
| Genetic bottleneck | - An event that causes a big reduction in a population
- Reduces no. of different alleles in the gene pool, reduces genetic diversity
- Survivors reproduce, large pop. created from new individuals |
| The founder effect | - Type of genetic bottleneck
- Describes what happens when just a few organisms from a population starts a new colony
- Where there is a small no. of alleles in gene pool
- Can be caused by geographical separation |
| Frequency of alleles in new colony | - Might be very different to frequency of alleles in original population
- So higher chance of genetic disease |
| Key factors of evolution | - Adaptation
- Selection |
| Reproductive success meaning | - No. of offspring an individual produces |
| Natural selection meaning | - Process where organisms that are better adapted to an environment will survive and reproduce
- There is differential reproductive success between the organisms with different alleles of the same gene |
| Natural selection process (1) | - Random mutation produces new alleles of a gene |
| Natural selection process (2) | - Many mutations are harmful or neutral but, under certain environmental conditions
- New alleles may benefit their possessor
- Leading to an increased chance of survival and increased reproductive success |
| Natural selection process (3) (ad-van-tae-jus) | - The advantageous allele is passed onto the next generation |
| Natural selection process (4) | - As a result, over several generations, the new allele will increase in frequency in the population |
| + Natural selection process (1) | - All offspring produce more offspring than required
- Population size of species remain relatively stable |
| + Natural selection process (2) | - There is a struggle for existence
- The offspring will have a gene pool - a variety of alleles |
| + Natural selection process (3) | - The fittest offspring (that have the most favourable alleles) are more likely to survive + reproduce |
| + Natural selection process (4) | - The offspring in turn are more likely to inherit the favourable alleles (and thus survive and reproduce)
- Over time the frequency of advantageous alleles increases
- Leads to evolution of new species |
