Tupes Of Selection Flashcards
What is selection
Process in which organism are better adapted to their enviroment and tend to survive and breed while those less adapted tend not to
What is directional selection
Directional selection favouring the individuals that vary in one direction from the mean of the population and changes the characteristics
What happens with direction selection when enviroment changes
The phenotypes of this best suited to the enviroment will survive those that fall either to left or right of distribution curve may have a phenotype which is more suited to the new enviroment so they’re likely to survive and breed and overtime the mean will move towards the direction of these individuals
Explain the directional selection in resistance to bacteria
A spontaneous mutation occurred in the allele of a gene of bacterium that allowed it to make a protein an enzyme which broke sown peniciloj before it was about to kill the bacterial cell
Bacterium happened by chance to be in a situation where penicillin was being used to reset an infection the mutation gave the individual the advantage to survive whilst the rest of the bacteria was killed
What happened to the bacteria that survived
It was able to divide by binary fission to buold a small population of penicillin resistant drugs they were more likely to survive in the press’s ncs of penicillin compared to other forms of bacteria
What happened to the population of resistant antibiotic
It increased at the expense of the non resistant also the allele frequency for resistance also increased
What is stabaliseing selection
If enviroment is stable the individuals with the closest phenotypes to the mean are favoured and are likely to pass on their alleles to next generation
And the extremities are less likely to be successful and reproduce and survives
What adaptions can occur
Anatomical shorter eats or thicker fur
Physiological oxidising fat rather than carbohydrates
Behavioural autumn migration of sewallows from uk to Africa to prevent food shortages
What is definition of stabilising selection
Selecting those close to the mean reserving the characteristics of the population and favouring the mean
