U4 T2 - Continuity of Life Flashcards
What is Evolution
The chane in the enetic composition of a population during succsessive generations, which may result in the development of a species.
What is Microevolution
Microevolution refers to the small-scalevariation of allele frequencies within aspecies or population
Macroevolution
Macroevolution is the variation of allelefrequencies at or above the species levelover geological time, resulting in thedivergence of taxonomic groups
What are the three types of phenotypic selection
stabilising, directional and disruptive
can the selection of allele frequency in a gene pool be positive or negative
Yessssss
When does natural selection occur
when the pressures of environmental selection confer a selective advantage on a specific phenotype to enhance its survival (viability) and reproduction (fecundity)
Explain Microevolution
Microevolution refers to the small-scalevariation of allele frequencies within aspecies or population
what 3 things can cause Microevolutionary change to occur
Mutation
Gene flow
Genetic drift
Explain microevolutionary change through mutation,
Mutation is the ultimate sourceof genetic variation, as itintroduces new alleles into apopulation
what is gene flow
Gene flow is the movement of genetic material between populations
Explain microevolutionary change through gene flow
Gene pools can change when individualsjoin or leave a population,
Such as migration of individuals, and thealleles they carry, can result in gene flow
Explain microevolutionary change through genetic drift
Genetic drift describes random fluctuations of alleles in a population over time (bottleneck effect, founder effect)
where is genetic drift more significant and why
Small populations with no gene flow, as random death of one individual cansignificantly alter the allele frequencies
what is an allele
The varying forms of a gene
whats a Genotype
The allele makeup for a particular characteristic
whats a Phenotype
the observable characteristics of an individual
What is natural selection
process wherebyindividuals with the mostfavourablecharacteristics (phenotype)have an increasedchance of surviving and reproducing(fecundity), compared with individualswith lessfavourablecharacteristics.
WHat are Selection pressures
external factors that affect an organism’s ability to survive in a given environment
positive selection
promotes the spread of beneficial alleles
Negitive selection
hinders the spread of deleterious alleles
WHat are the 3 types of selection
stabilising, directional and disruptive
When does Stabilising selection occur
Stabilising selection occurs when intermediate phenotypes are favoured over extreme phenotypes
when does Directional selection occur
Directional selection occurs when a phenotype on one side of the bellcurve is favoured
when does Disruptive selection occur
Disruptive selection occurs when extreme phenotypes on both ends of the bellcurve are favoured over intermediate phenotypes
what does genetic drift discribe
random fluctuations of alleles in a population over time
When does genetic isolation occur
when there is nogene flow between two populations – thegene pools are isolated from eachother
what is Spatial isolaiton
occurs between populations that are separated by great distances, but it can also take place between populations that inhabit different parts of the same area.
what are the two types of Repoductive isolation and explain them
Hybrid inviability-
Hybrid offspring of different species may be non-viable or show limited development
Hybrid infertility-
When interbreeding between individualsfrom different species results in offspring, theyare called hybrids and are generally sterile
Temporal isolation
the misalignment of reproductive systems between indivisuals or populations
what is Speciation
Speciation is the evolutionary process by which populations evolve to become distinct species.
what are the three modes of Speciation
Allopatric
Sympatric
Parapatric
how does Allopatric speciation occur
when ageographical barrier dividesa population
when does Parapatric speciation occur
When populations maintain a zone of contact but the area is large with significant variation in habitat conditions
when does Sympatric speciation occur
when there are no physical barriers preventing any members of a species from mating with another, and all members are in close proximity to one another
What are the four patterns of Diversification
Divergent
Convergent
Parallel
Coevolution
what is Divergent evolution
the differentiation of distinctly different species/populations from a common ancestral species
what is Convergent evolution
Convergent evolution is the evolution of similarfeaturesin unrelated groups of organisms
when does Parallel evolution occur
when related species evolvesimilar features independently
when does Coevolution occur
two speciesevolving together in a reciprocal responseto various selection pressures
what is the bottle neck effect
The bottleneck effect describes theimpact on the remaining population
Because of the reduced populationsize, the possible reproductive pairingsare limited, which leads to high levelsof inbreeding
This results in reduced variation and an increased risk of extinction
The smaller the population, the greaterthe bottleneck effect
Alleles can be lost from the gene pool
