AQA A Level Biology: Genetic Diversity and Adaptation Flashcards
What is genetic diversity?
The number of different alleles of genes in a population.
Why is genetic diversity important?
It increases the chances of a population surviving changes in the environment.
How is genetic diversity created?
Through mutations and gene flow from different populations.
What is a gene mutation?
A change in the base sequence of DNA that creates new alleles.
What is gene flow?
The movement of alleles between different populations.
What is a population?
A group of organisms of the same species that occupy the same area and can interbreed.
What is the founder effect?
A loss of genetic diversity that occurs when a small group of individuals establishes a new population.
Why does the founder effect reduce genetic diversity?
The new population has a smaller gene pool, so fewer alleles are available.
What is a genetic bottleneck?
A sharp reduction in population size due to a catastrophic event that reduces genetic diversity.
What happens to genetic diversity after a bottleneck?
It is reduced because many alleles are lost from the gene pool.
What is natural selection?
The process by which individuals with advantageous alleles are more likely to survive, reproduce, and pass on their alleles.
What is directional selection?
Selection that favors individuals with an extreme phenotype, shifting the population’s mean.
Give an example of directional selection.
Antibiotic resistance in bacteria.
What is stabilising selection?
Selection that favors the average phenotype and eliminates extreme traits.
Give an example of stabilising selection.
Human birth weight, where extremely high or low weights reduce survival chances.
What is disruptive selection?
Selection that favors individuals at both extremes of a phenotype, leading to two distinct forms.
What is adaptation?
A trait that increases an organism’s chance of survival and reproduction.
What are the three types of adaptations?
Anatomical, physiological, and behavioral.
What is an anatomical adaptation?
A physical feature that increases survival, such as thick fur in polar bears.
What is a physiological adaptation?
A process inside an organism’s body that increases survival, such as producing enzymes in extreme environments.
What is a behavioral adaptation?
A way an organism acts to increase survival, such as migration or courtship displays.
How does genetic diversity affect adaptation?
Populations with greater genetic diversity are more likely to adapt to environmental changes.
What is selective pressure?
An environmental factor that affects the survival and reproduction of organisms.
What happens to allele frequencies during natural selection?
Beneficial alleles increase in frequency over generations.
What is evolution?
The change in allele frequencies in a population over time.
How can genetic drift affect small populations?
It can cause random changes in allele frequencies, reducing genetic diversity.
What is the difference between natural selection and genetic drift?
Natural selection is directed by environmental pressures, while genetic drift is random.
Why are small populations more affected by genetic drift?
Random changes have a greater impact due to fewer alleles in the gene pool.
What is the role of mutation in evolution?
It introduces new alleles that may be beneficial, harmful, or neutral.
How does genetic diversity contribute to speciation?
It allows populations to diverge and develop into distinct species over time.
