IB Bio - Genetics and Evolution

gene pool

sum total of all the alleles of all the genes present in a population

allele frequency

relative frequency of a particular allele (in comparison to the other alleles of the same gene) in a population

genetic drift

change in alleles frequency in a gene pool of a population due to chance events. can occurs in two situation: the bottleneck effect and founder effect

bottleneck effect

when natural disasters lead to a sudden decrease in the population that may not represent the genetic diversity of the original population

founder effect

when a small subset of a population breaks away from the larger population to colonize a new area and the population that branches off may not be an exact genetic representation of the original population

neo-darwinism

the combined work of many scientists to explain natural selection on the foundation of mendelian genetics

stabilizing selection

natural selection that favours the average individual with intermediate forms of the trait and eliminates extreme forms

directional selection

favours one extreme form id the trait over all other forms

disruptive selection

natural selection where both extremes forms of the traits are favoured over the intermediate form

artificial selection

when people select traits to be represented in the next generation

linked genes

genes that are found on the same chromosome and are close togethef

unlinked genes

genes that are found on different chromosomes

dihybrid cross

the inheritance of two traits

gene loci

specific location of a gene in a chromosome

discrete variation

traits where individuals are clearly one phenotype or another

continuous variation

a spread called a normal distribution that is plotted as a bell-curve

polygenic inheritance

when a trait is controlled by many genes interacting together

speciation

the process by which new species arise

reproductive isolation

a driver of speciation when barriers prevent populations of the same species from interbreeding

allopatric speciation

speciation from geographical factors

sympatric speciation

speciation that happens in the same location due to isolating mechanisms

temporal isolation

a type of reproductive isolation that results from differences in timing of the reproductive cycle

behavioural isolation

a type of reproductive isolation that results from environmental factors

adaptive radiation

evolution of multiple new species from an ancestral species to occupy different ecological niches

hybridisation

interbreeding between two different species that leads to a new species

polyploidy

when a diploid cell or organism acquired one or more additional sets of chromosomes

allopolyploidy

a special case of polyploidy where a hybrid has multiple chromosomes sets that are derived from the different parental species