Selection And Evolution Flashcards
Discontinuous variation
Differences between individuals of a species in which each one belongs to one of a small number of distinct categories with no intermediates
Continous variation
Differences between individuals of a species in which each one can lie at any point in the range between the highest and lowest values
Natural selection
The process by which individuals with a particular set of alleles are more likely to survive and reproduce than those with other alleles
Selection pressure
An environmental factor that affects the chance of survival of an organism
Biotic factor
An environmental factor caused by living organisms
Competition
The need for a resource by two organisms when the resource is in short supply
Abiotic factor
An environmental factor that is caused by non living components
Eg light intensity, soil pH etc
Phenotypic variation
Differences between the observable characteristics of individuals within a species
Disruptive selection
Natural selection that maintains relatively high frequencies of two different sets of alleles
Stabilising selection
Natural selection that tends to keep allele frequencies relatively constant over many generations
Directional selection
Natural selection that causes a gradual change in allele frequency over many generations
For eg if a new environmental factor or a new allele appears
Founder effect
The reduction in a gene pool compared with the main populations of species resulting from only 2 or 3 individuals starting of a new population
Genetic drift
The gradual change in allele frequencies in a small population where some alleles are lost or favoured just by chance and not by natural selection
Evolutionary bottleneck
A period when the numbers of a species fall to a very low level resulting in the loss of a large number of alleles and therefore a reduction in the gene pool of the species
Inbreeding depression
A loss of the ability to survive and grow well due to breeding between close relatives
