Genetic Diversity and Adaptation Flashcards
Define genetic diversity
The number of different alleles of genes in a population, it is a factor enabling natural selection to occur
What are alleles? How do they arise
Variations of a particular gene (same locus), that have different DNA base sequences
They arise by mutation
What is a population
A group of organisms of the same species in a particular space at a particular time that can interbreed to produce fertile offspring
Describe the process of natural selection
Random mutations can result in new alleles of a gene, this causes genetic variation
Selectional pressures exist, so some alleles may be of benefit to organisms
This gives an organism increased reproductive success and the advantageous allele is inherited by the next generation
The frequency of the new allele then increases in the population
What are the 3 types of natural selection
Directional selection
Stabilising selection
Disruptive selection
Explain the importance of genetic diversity
Genetic variation enables natural selection to occur, and in certain environments a new allele might be of benefit to its possessor
By resulting in a change in the polypeptide coded for which positively changes its properties , the possessor now has a selective advantage
What is a selective advantage
An increased chance of survival and reproductive success due to an advantageous allele
What is evolution
A change in the allele frequency (how common it is) over many generations in a population, occurring through the process of natural selection
How does stabilising selection work
In a stable environment, selection operates against both extremes of a range. This reduces variability
Stabilising selection, birth mass of babies example
Random mutations lead to genetic variation
The extreme phenotypes of very high and very low birth weight are selected against
The extreme organisms are less likely to survive are therefore have lower reproductive success
This means they are less likely to pass on their alleles so the frequency of extreme alleles decreases
How does directional selection work
Individuals at one extreme end could have an advantage and the other end a disadvantage, so the mean and range of values shift towards the favoured extreme
Directional selection, antibiotic resistance example
Random mutations lead to genetic variation
The extreme phenotype (bacterial cells which are not resistant) are selected against
The extreme organisms are less likely to survive are therefore have lower reproductive success
This means they are less likely to pass on their gene so the frequency of extreme genes decreases
Describe 3 types of adaptations
What is an anatomical adaptation
Structural/physical features which increase chance of survival
What is an physiological adaptation
Processes/chemical reactions that increase chance of survival
