Variation Flashcards
what are the three types of variation among individuals
- genetic variation
- environmental variation
- genotype-by-environment interaction
types of variation - genetic variation
- the result of differences among individuals that are encoded in their DNA
- the instructions written in different individuals’ genes may specify different versions of particular proteins, or they may specify the manufacture of certain proteins in different quantities or different times or places
types of variation: genetic variation - can it evolve
types of variation - environmental variation
- arises when external factors influence how much protein is made from particular genes, or how the proteins work
- when individuals experience different environmental, they make different amount of proteins or show differences in protein function
- cannot evolve
types of variation: environmental variation - can it evolve
- no
- DNA between individuals are different and environmental variation shapes phenotypes, not genes
- does not have I in VIST
types of variation - genotype-by-environmental interaction
- result of differences among individuals that are encoded into their DNA and that make them differ in their sensitivity to environmental influences
- different individual thus react different to a changing environment
types of variation: genotype-by-environment interaction - can it evolve
- yes
- differences in genes and the environment shapes the phenotypes
define a qualitative trait
- discrete
- complete dominance and may be one intermediate
define quantitative trait
- continuous
- multiple genes work together to create a single phenotype
- is polygenic
define quantitative genetics
- the genetics of continuously vary characters
or - the study of the genetic basis underlying phenotypic variation among individuals
quantitative genetics - define quantitative traits
- they are polygenic
- there are environmental effects that alter the phenotypic state of each individual
- value varies continuously
environmental variation - phenotypic plasticity
ability of 1 genotype to produce multiple phenotypes in response to different environments
environmental variation: phenotypic plasticity - how do we visualize it
- reaction norms
- the slope of the line = plasticity
environmental variation - what causes differential gene expression
exposure to different environments
environmental variation - wat is an inducible defense
- example of plasticity
- when organisms turn on defenses in response to chemical cues of predators
define epigenetics
epigenetic markers can influence gene expression and therefore phenotypes and these can be inherited
what is the variation of phenotypes ( Var(P) ) equal to?
Var(P) = Var(G) + Var(E) + Var(GxE)
genotype-by-environment interaction - how do you read it on a reaction norm
the two slopes cannot be the same
what does selection act on
- phenotypes
- individuals
where do we measure genetic variation and change in allele frequencies
- genetic and phenotype
- population
what can evolve
genetic and gene-by-environment interaction
genotype-by-environment interaction - how may it evolve?
- when populations have genetic variation for environmental sensitivity, populations can evolve greater or less plasticity
what kinds of environmental do youthink would select for high vs low plasticity
- high: dynamic environments that are always changing
- low: more stable environments
within a species (or population), what does selection tend to do to a trait?
selection tends to erode variation
what helps maintain variation
- GxE
- balancing selection
what helps maintain variation - balancing selection
- preserves genetic variation by maintain two or more phenotypic forms in a population
- ex: negative-frequency-dependent-selection
what helps maintain variation: balancing selection - negative-frequency-dependent-selection
the fitness of any genotype in a population declines if it becomes too common in the population
