Genetic diversity Flashcards
rDefine genetic diversity
The number of different alleles in a population
This is a factor which enables natural selection to occur
Describe the process of natural selection
Random mutations occur within the population.
This introduces genetic variation to the population.
While some mutations are harmful, others provide organisms with an advantage to survive in their environment.
The new allele provides a reproductive selective advantage. Therefore, the individual with the allele is more likely to reproduce and pass the allele onto their offspring.
Over many generations, there will be an increase in the frequency of this allele within the population.
What is the gene pool?
The collection of all genes and alleles in a population at a particular time.
What is the allele frequency?
What is selection?
The process by which organisms that are better adapted to their environment tend to survive and breed
Every organism is subjected to the process of selection based on its suitabilty of surviving the conditions faced at the time
Different environmental conditions favour different charcteristics in the population
What is directional selection?
When selection favours individuals which vary in one direction from the mean of the population
This changes the characteristics of the population
Describe the basis of directional selection
When enviroments change, the phenotype which is best suited to these new conditions are more likely to survive
Some individuals which fall either right or left of the mean possess a phenotype more suited to the new conditions
These are then more likely to reproduce offspring and survive
More of these alleles are then contributed to further generations
Over time, the mean will then move in the direction of these individuals
Describe directional selection in terms of antibiotic resistance
A random mutation creates an allele that provides bacteria in a population resistance to an antibiotic
If this population of bacteria is then exposed to this antibiotic , only those with the resistance allele survive and rest will die
This allele is then passed on through many generations of bacteria until most bacteria carry this allele
Describe stabilising selection
When the middle trait has the selective advantage and therefore continues to be most frequent in a population
The range of the graph will decrease as extreme traits are lost over time
Describe stabilsing selection in terms of birth weight
A middling birth weight is the selective advantage as extremely low birth weight may be disadvnatgeous to survival due to the underdevelopment of the baby, and an extremely high birth weight may also be disadvantegous as there may be complications in birth
This means middling weight is the most advnatgeous as they can survive and pass on their alleles to offspring anf future generations
