3.4.4 (genetic diversity and adaptation) Flashcards
Genetic diversity
The number of different alleles and genes in a population
Natural selection
Random mutation results in a new allele
New allele may be beneficial leading to increased reproductive success
Advantageous allele is inherited by offspring
Over many generations the new allele increases in frequency within the population
Bottleneck effect
When a population is reduced by a large amount
Reduces the number of alleles present in the population and therefore genetic diversity
Causes a change in allele frequency
The founder effect
When a few organisms leave a population starting a new population
Therefore less alleles are present in the new population
Changes the frequency of alleles within a population
Types of adaptation
Behavioural
Physiological
Anatomical
Name 2 types of selection
Directional
Stabilising
Stabilising selection
Keeps allele frequencies constant
Individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
Example is human birth weigh- very low and very high birthweights are selected against leaving to maintenance of intermediate birthweights
Directional selection
Produces a gradual change in allele frequencies over many generations
Usually occurs due to a change in selection/environment pressures or a new advantageous allele has appeared
Individuals with alleles for characteristics of an extreme type are more likely to survive and reporduce
An example is antibiotic resistance
Describe antibiotic resistance as an example of directional selection
Some bacteria have alleles for antibiotic resistance
Population exposed to antibiotic killing those without resistance
Resistance bacteria survive and reproduce passing on resistant allele to next generation
After time most of population has resistant allele
