18.2 — variation in phenotype Flashcards
what does the term ‘variation’ refer to?
variations refers to the differences observed among individuals within any given population
what is genetic variation?
variation due to the genes and alleles an individual possesses
what are the sources of genetic variation?
- mutations — changes to genes and chromosomes that may be passed on to the next generation
- meiosis — new combinations of alleles present in the gametes formed, produced by independent assortment of chromosomes and crossing over between chromotides
- random fertilisation — random fertilisation of gametes produces new combinations of alleles in a zygote
- random mating
how do mutations create genetic variations?
by changing genes and chromosomes that may be passed on to the next generation
how does meiosis create genetic variations?
can create new combinations of alleles present in the gametes formed, produced by independent assortment of chromosomes and crossing over between chromotids
how does random fertilisation create genetic variations?
random fertilisation of gametes produces new combinations of alleles in a zygote
what is environmental variation?
variation caused by the enviroment in which an organism lives
what enviromental factors can cause variation?
- light
- nutrient and food availability
- temperature
- rainfall
- soil conditions
- pH
how can the effect of genetic and environmental factors impact variation?
enviromental factors can influence how genetic factors are expressed
why is it hard to distinguish between the effects of genetic and environmental influences?
as many combine to produce differences between individuals
what are polygenes?
different genes at different loci that all contribute to a. particular aspect of phenotype
what type of variation is the combined effect of multiple genes common in?
continuous variation
