Topic 4C Flashcards
beneficial mutations can result in:
adaptations to environment over time
fitness
a measure of the extent to which an individual’s genotype is represented in the next generation
positive selection
natural selection that increases the frequency of a favourable allele
sometimes, natural selection can promote the fixation of advantageous alleles, meaning:
the allele has a frequency of 1
negative selection
natural selection that reduces the frequency of a deleterious allele
balancing selection
natural selection that acts to maintain two or more alleles of a given gene in a population
heterozygote advantage
a form of balancing selection in which the heterozygote’s fitness is higher than that of either of the homozygotes, resulting in selection that ensures that both alleles remain in the population at intermediate frequencies
artificial selection is a form of:
directional selection
intrasexual selection
a form of sexual selection involving interactions between individuals of one sex, as when members of one sex compete with one another for access to the other sex
intersexual selection
a form of sexual selection involving interaction between males and females, as when females choose from among males
migration
the movement of individuals from one population to another
gene flow
the movement of alleles from one population to another through interbreeding of some of their respective members
migration _______ genetic variation between populations
reduces, may be maladaptive and decrease population’s average fitness for their particular local conditions
mutation ______ genetic variation
increases
genetic drift
the random change in allele frequencies from generation to generation
bottleneck
an extreme, usually temporary, reduction in population size that often results in marked genetic drift
founder event
a type of bottleneck that occurs when only a few individuals establish a new population
genetic drift leads to allele frequency changes and therefore evolution but it does not lead to…
adaptations since the alleles whose frequencies are changing as a result of drift do not affect an individuals ability to survive or reproduce
genetic drift is much more significant in:
small populations (samples)
non-random mating alters:
genotype frequencies without affecting allele frequencies (no new alleles are added or taken away)
inbreeding depression
a reduction in fitness resulting from breeding among relatives causing homozygosity of deleterious recessive mutations
biological species concept (BSC)
species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups (i.e. a closed gene pool)
morphospecies concept
the idea that members of the same species usually look like each other more than like other species
how come the BSC cannot be applied to Bacteria and Archaea?
because they reproduce asexually: there is not exchange of genetic information
ring species
species that contain populations that are reproductively isolated from each other but can exchange genetic material through other, linking populations
hybridization
interbreeding between two different varieties or species (results in hybrid offspring with distinct phenotypes)
ecological species concept (ESC)
the concept that there is a one-to-one correspondence between a species and its niche
phylogenetic species concept (PSC)
the idea that members of a species all share a common ancestry and a common fate
pre-zygotic isolation
describe factors that prevent the fertilization of an egg
post-zygotic isolation
describes factors that cause the failure of the fertilized egg to develop into a fertile individual
most species are reproductively isolated by:
pre-zygotic isolating factors
behaviourally isolated
describes individuals that only mate with other individuals on the basis of specific courtship rituals, songs, and other behaviours (pre-zygotic)
gametic isolation
incompatibility between the gametes of two different species (pre-zygotic)
mechanical incompatibility
structural configuration of the genitalia that prevents mating with another species (pre-zygotic)
temporal isolation
pre-zygotic isolation between individuals that are reproductively active at different times
geographic isolation
spatial segregation of individuals (pre-zygotic)
ecological isolation
pre-zygotic isolation between individuals that specialize ecologically in different ways
genetic incompatibility
genetic dissimilarity between two organisms, such as different numbers of chromosomes, that is sufficient to act as a post-zygotic isolating factor
speciation is a by-product of:
the genetic divergence of separated populations, it is the development of reproductive isolation between populations
partially reproductively isolated
describes populations that have not yet diverged as a separate species but whose genetic differences are extensive enough that the hybrid offspring they produce have reduced fertility or viability compared with offspring produced by crosses between individuals within each population
allopatric speciation
speciation resulting from populations that are geographically separated from each other
subspecies
allopatric populations that have yet to evolve even partial reproductive isolation but which have acquired population-specific traits
dispersal
the process in which some individuals colonize a distant place far from the main source population (cause of allopatric speciation)
vicariance
the process in which a geographic barrier arises within a single population, separating it into two or more isolated populations (cause of allopatric speciation)
peripatric speciation
associate with dispersal
a specific kind of allopatric speciation in which a few individuals from a mainland population disperse to a new location remote from the original population and evolve separately
mainland population
the central population of a species
island population
an isolated population
adaptive radiation
a period of unusually rapid evolutionary diversification in which natural selection accelerates the rates of both speciation and adaptation in a single lineage
co-speciation
a process in which two groups of organisms speciate in response to each other and at the same time, producing matching phylogenies
sympatric
describes populations that are in the same geographic location
sympatric speciation
occurs as a result of disruptive selection, because even though gene flow occurs, the hybrids are selected against
instantaneous speciation
speciation that occurs in a single generation ex. offspring is polyploid
polyploidy
the condition of having more than two complete sets of chromosomes in a genome
allopolyploids
polyploids produced from hybridization of two different species
autopolyploids
polyploids derived from an unusual reproductive event between members of a single species
