Exam 2 Flashcards
phenotypic plasticity
single genotype can lead to multiple different phenotypes depending on the environment
developmental plasticity
fixed, often irreversible, happens during early development
acute plasticity
short term, reversible
genotype norm of reaction
a curve that relates the contribution of environmental variation to observed phenotypic variation
three types of phenotypic distribution
continuous variation, polymorphism/polyphenism, canalization
polymorphism/polyphenism
discontinuous genetic variation resulting in the occurrence of several different forms or types of individuals among the members of a single species. opposite of genetic fixation
canalization
fixed trait, same phenotype regardless of environmental variation
four major types of phenotypic plasticity
shifts in phenology, acclimation/acclimatization, polyphenism, transgenerational plasticity
phenology
timing of life history events, such as flowering time or clutch laying
acclimation
physical adjustment to a controlled change in one specific environmental variable, occurs in a lab
acclimatization
physical adjustment to changes in multiple environmental variables in nature
transgenerational plasticity
initiated in past generations, but has consequences in current and future generations, such as maternal effects and epigenetic inheritance. Often genetic, but driven by environmental effects
maternal effects
phenotype of the offspring is influenced by the environment experienced by the mother (and thus her phenotype)
proximate drivers of phenotypic plasticity
gene expression and allelic sensitivity
gene expression (relative to phenotypic plasticity)
upregulation or downregulation by transcription factors of specific genes in response to environmental stimuli, often through the action of regulatory genes
can influence allelic sensitivity, and can be heritable
allelic sensitivity
the downstream product (protein or messenger RNA) of a particular allele responds directly to environmental stimuli. For example: in response to an environmental change, a protein changes its binding site to no longer allow binding
Not as important as gene expression. Allelic sensitivity is rare because homeostasis is good.
why aren’t all traits plastic?
plasticity has costs
3 costs of phenotypic plasticity
It costs energy to synthesize new proteins, to break down those proteins when they are not needed, and to maintain the cellular machinery that detects environmental stimuli.
Trade-offs whereby plasticity in a particular trait increases survival but reduces fecundity, or vice versa
The plastic response might “misfire” in response to the wrong environmental cue.
under what conditions should developmental plasticity be expected?
non-mobile organisms, environmental variation that is high, predictable, and occurs within the lifespan of the organism
under what conditions should acute plasticity be expected?
unpredictable changes and stable environments
climatic variability hypothesis
thermal tolerance (climate niche) correlates with latitude
is behavior considered plasticity?
we don’t know
behavioral drive
Behavioral flexibility leads to the exploitation of new niches and faster evolutionary diversification
behavioral inertia
Behavioral flexibility causes individuals to track their niche and “hide” from selection, reducing evolutionary diversification. Example: behavioral thermoregulation - changing micro-environment (dark rocks, shade, etc.)