Unit 4: A.O.S.2: SAC 4: Population Genetics Flashcards
What is a population?
A population is a group of individuals of a species the can interbred. These individuals live in one region at a particular time.
What is allele frequency?
Allele frequency is the rate of occurrence of specific alleles in a population. Alleles are the different forms of a particular gene.
What is a species?
A species is a group of closely related organisms that are very similar in characteristics and a real capable of interbreeding.
What is the gene pool?
The gene pool is the sum total of genetic information present in an interbreeding population.
What is natural selection?
Natural selection is a mechanism for change in allele frequency that is best observed in a small population with limited gene flow. Natural selection is based on the concepts of Darwinism.
What is selection pressure in natural selection?
External agents which affect the ability of an organism to survive are referred to as selection pressures
Selection pressures can be negative and decrease the occurrence of a trait, or beneficial and increase its proportion within a population
Types of selection pressures include:
Resource availability: Presence of sufficient food, habitat and mates
Environmental conditions: Temperature, weather conditions or geographical access
Biological factors: Predation and disease
What is selective advantage in natural selection?
The characteristic of an organism that enables it to survive and reproduce better than other organisms in a population in a given environment; the basis for evolution by natural selection.
What is adaptation in natural selection?
An adaption is any alteration in the structure or function of an organism that results from natural selection and by which the organism becomes better fitted to survive in its environment.
What is gene flow?
Gene flow is the movement of genes into or out of a population owing to migration; can result in changes in allele frequencies in a gene pool if an unrepresentative sample of the original population migrates.
What is genetic drift?
Not all individuals are able to contribute their genes to the next gene. As a result random changes occur in allele frequency. These random changes are referred to as genetic drift. In small, interbreeding populations genetic drift may have pronounced affects on allele frequency. Alleles may become:
- lost from the gene pool
- fixed as the only allele present in the gene pool
What is the bottleneck effect?
The bottleneck effect is when a large population is put through a figurative “bottleneck”. This bottleneck causes the population to become smaller. Even though the population may recover, pronounced effects on allele frequency will have occurred.
What is the founder effect?
The founder effect involve random chance effects occurring to allele frequencies as a result of a population being formed from a small unrepresentative sample of a larger population.
What are the concepts of Darwinism?
- overproduction:
Species produce more young than will survive to reproductive age. - variation:
Individuals vary from one another in many characteristics. Some are better suited than others to the conditions of the time. - competition:
Among offspring for resources. - survival of the fittest phenotype:
The individuals with the most favourable combinations of characteristics will be most likely to survive and pass their genes to the next generation. - favourable combinations increase:
Each new generation will contain more offspring from individuals with favourable characteristics.
