4.4 Genetic diversity and selection Flashcards
what is genetic diversity
the number of different alleles for a gene in a population
what is natural selection and how does it occur
- there is genetic diversity in the population
- new alleles arise due to random mutation
- the population experiences selection pressure
- individuals with the advantageous allele survive to reproduce
- the advantageous allele is inherited by offspring
- therefore, over many generations, the advantageous allele increases in frequency in the population
what are adaptations that can occur for survival
- anatomical
- physiological
- behavioural
what are anatomical adaptations
fur colour, neck length
what are physiological adaptations
rate of gas exchange, muscle contraction efficiency
what are behavioural adaptations
courtship displays
how do species characteristics change
- all organisms have a range of phenotypes
- for polygenic traits, the observed phenotypes show normal distribution
- stabilising selection or directional selection can occur
what is stabilising selection
the intermediate (middle) phenotypes are best adapted to survival in the environment so are advantageous
- the intermediate phenotypes are more common and extreme phenotypes may disappear
example of stabilising selection
birth mass in humans
what is directional selection
- an extreme phenotype is best adapted to survival in the environment so a particular allele is advantageous
- the extreme phenotypes become more common
example of directional selection
antibiotic resistance in bacteria
