Population variation 2 Flashcards
What is adaptive evolution?
a change in the phenotypic constitution of a population owing to selection on heritable variation among phenotypes that changes the genotypic constitution of the population
if all individuals were phenotypically identical, there would be no opportunity for ________
if all individuals were genotypically identical, there would be no opportunity for ___________
if all individuals were phenotypically identical, there would be no opportunity for selection
if all individuals were genotypically identical, there would be no opportunity for evolution
Phenotypic variation results from both …..
environmental AND genetic influences
phenotypic variation within populations is either ………
discrete or quantitative/continuous
What is discrete variation?
- polymorphism
- multiple phenotypes that can be places into distinct categories
what is continuous vatiation?
- quantitative characters
- where multiple loci produce a trait, and the trait varies continuously in the population
how does environment effect phenotypic variation?
- directly affects the development or expression of features
- may be permanent effects (nutrition affects height and growth, etc)
- some may be before hatching/birth as well (fetal alchohol syndrome)
both _____ and _____ can lead to continuous variation of additive traits
GENETIC AND ENVIRONMENT
traits regulated by more loci and/or influenced by environment tend to have …….
smooth continuous variation
What are non-genetic effects of mothers on offspring?
- environmental, maternal effects!
- amount/composition of yolk
- degree of maternal care
- maternal physiological condition while carrying embryos
Varieties can differ greatly from ___________, while still being the same _____________
Varieties can differ greatly from place to place, while still being the same species
What are subspecies?
a recognizable distinct population occupying a different geographic area from others of the same species
What are the three types of geographic variation among species?
- sympatric
- parapatric
- allopatric
What is sympatric geographic variation?
- populations with overlapping geographic distributions
- occupy the same area, and frequently encounter each other
- BUT they have genetic differences
What is parapatric geographic variation?
- populations with adjacent by non-overlapping geographic ranges that come into contact
What is allopatric geographic variation?
- populations with separated distributions
In the absence of _________, selection does not occur
VARIATION
What are forces that add to genetic variation? take away?
- add: mutation, and gene flow
- take away: gene flow, drift, selection
How is genetic variation maintationed?
- diploidy (two copies of alleles, so more variation even if some of it is ‘hidden’ due to heterozygosity)
- neutrality, some variants have no selection against them
- gene mixing (both sexual and asexual)
what is linkage disequalibrium?
- tendency of traits to be inherited together!
- the closer two alleles are, the more likely they are to be inherited together
how is genetic variation maintained/gained in asexual inheritance?
- horizontal gene transfer
Why is genetic variation important?
- it adds to the potential for change in genetic structure
- allows for adaptation to environmental change
- allows divergence of populations, biodiversity
