4.4 Genetic Diversity and Adaptation Flashcards
What is genetic diversity?
The total number of different alleles within a population
What is a gene pool?
The total number of all alleles of all the individuals in a population at a set time
What is allele frequency?
The proportions of the different alleles in the gene pool
What is population?
Group of individuals of the same species that live in the same place
What is a species?
Individuals that can interbreed to produce fertile offspring
What is an allele?
Different forms of a gene
What is natural selection?
The natural process of stronger alleles surviving because they are better adapted to their environment
Therefore breeding which increases the frequency of those advantageous alleles in the next generation
What is reproductive success?
Successfully producing fertile offspring
What is fitness?
Ones that survive to reproduce
Why is having a greater genetic diversity in a population better for its chance of survival?
More variety = more alleles in the population
Therefore with environmental change one individual may have an allele that would allow them to survive
What can happen to populations with a low genetic diversity?
They are very vulnerable
Can lead to a genetic bottleneck eg cheetahs
What changes allelic frequency in a population over time?
Natural selection
Survival of the fittest
As environmental change leads to selection and advantageous alleles survive to reproduce
Therefore allele frequencies will change and only some are passed to the next generation
What decides if an allele is advantageous?
Depends on the environmental conditions at any one time
What are the stages of natural selection?
Variation Mutation Environmental change Competition Survival Reproduction Alleles
What pneumonic helps remember natural selection?
Very Massive Eagles Can Soar Really Aggressively
What are the types of selection?
Directional
Stabilising
Disruptive
What is directional selection?
Selection that favours a phenotype best suited to a changing environment at one extreme of the population
This results in changes to the characteristics of a population as these individuals are more likely to survive and breed - pass on their alleles
The ‘mean’ will therefore shift
What is stabilising selection?
Selection against both extremes (eliminating extreme phenotypes) associated with non-changing/stable environments over many years
Those closest to the mean are more likely to pass their alleles on - maintaining favourable characteristics = a successful species
The range and distribution becomes smaller and narrower
What is a normal distribution?
A bell shaped curve produced when a certain distribution is plotted on a graph
What is an example of directional selection?
Antibiotic resistance
The bacterium that were resistant survived to reproduce
Therefore their population became greater than the non-resistant bacteria
What is an example of stabilising selection?
Birth mass of babies
The mortality rate of babies is high at the two extremes of very underweight and very overweight
What are the types of adaptations from natural selection?
Anatomical
- short ears, thick fur
Physiological
- different biomolecules as sources of energy
Behavioural
- migration of swallows
