Unit 4 Genetic Diversity Flashcards
Describe what is meant by genetic diversity
Genetic diversity is the number of different alleles of genes in a population
- Is the enabling factor for natural selection to occur
Define an allele
- Different forms of a particular gene found at the same locus position on a chromosome
- Single gene can have many alleles
Describe what is meant by natural selection
- Natural selection is the process that leads to evolution within populations as species being better adapted to their environment
- Adaptations can be anatomical, physiological, or behavioural
Describe the PRINCIPLES of natural selection
- New alleles for a gene created by random mutations
- Some alleles provide an advantage, making an individual more likely to survive and reproduce
- Reproduction passes advantageous allele onto next generation &frequency of allele increases in population
Describe what is meant by directional selection
- Occurs when environmental conditions change
- Individuals with alleles for characteristics of an extreme type more likely to survive
Give an EXAMPLE of directional selection.
Antibiotic resistance
1. Some bacteria have alleles for resistances due to mutation
2. Non-resistant bacteria die and resistant bacteria survive/reproduce and pass on resistance allele
3. High frequency of resistance allele in bacterial population
Describe what is meant by stabilising selection.
- Individuals with phenotypes closest to mean are favoured & new characteristics are not favoured
- Results in low diversity as standard deviation decrease
Give an example of stabilising selection
e. g Birth weight - very small & very large babies less likely to survive than medium sized
- Extreme mass babies least likely to survive and reproduce and so less likely to pass on their alleles for extreme mass
- so alleles for extreme mass at birth decrease in frequency in the population
