Exam Two Flashcards
Differing phenotypes for one genotype
Phenotypic plasticity
A curve that relates the contribution of environmental variation to observed phenotypic variation
Norm of reaction
When changes in phenotype are irreversible from one individual to another
Developmental plasticity
Differing phenotypes within one species
Polymorphism
No phenotypic plasticity even with changes to the environment (can evolve but no plasticity) (ex: living fossils)
Canalization
The study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life
Phenology
More abundant phenotypic plasticity
Shifts in phenology as to be more flexible with changing environments
In the lab and can control for one environmental attribute
Acclimate
Is in a natural population where it is difficult to pick out one specific environmental attribute
Acclimatization
A type of phenotypic plasticity; plastic development of discrete phenotypes or morphs
Polyphenism
Does transgenerational plasticity persist?
No
Up regulation or down regulation of specific genes in response to environmental stimuli, often through the action of regulatory genes
Gene expression
Downstream products
Proteins, mRNA, etc.
When the downstream product of a particular allele responds directly to environmental stimuli
Allelic sensitivity
why aren’t all traits in all organism’s plastic?
Phenotypic plasticity has a COST in the form of energy that could be used other places such as for growth
Plasticity in a particular trait increases survival but reduces fecundity and the plastic response might “misfire” in response to the wrong environmental cue
Plastic responses are not ALWAYS beneficial
Under what conditions should we expect developmental plasticity to evolve?
Non-mobile organisms
Unpredictable environment. What kind of plasticity?
Acute plasticity
Climatic variability hypothesis
o Broader at high latitude
o Specific to low latitude
Is behavior a type of phenotypic plasticity?
We do not truly know as behavior could be genetically predetermined
Good examples are birds as they will diversify into new environments if they are behaviorally flexible
Behavioral flexibility leads to exploitation of new niches and faster evolutionary diversification
Causes evolution and speciation to be more rapid
Behavioral drive
Good example is lizards who can live in different environments and use thermoregulation behavior
Behavioral flexibility causes individuals to track their niche and “hide” from selection, reducing evolutionary diversity
When evolution is slowed in a species
Behavioral inertia
Traits that appear with a specific environment occurs. Loci are always there waiting for this environment to use and create this new phenotype. Genes will be “turned on” when they enter the new environment and are stimulate and thus allows these new phenotypes to occur
Cryptic genetic variation
Any adaptive change in the environmental regulation of a phenotype which can be positive or negative
Genetic accommodations
Subcategory of accommodation selection for reduced regulation of trait and it is completely genetically canalized or the complete loss of plasticity through genetic assimilation. This focuses on the negative (look at Figure 1 from notes and paper)
Genetic assimilation
Evolution is slow
Gradualist
Evolution is fast
Contemporary evolution
Examples of fast evolution
Guppies in Trinidad and Galapagos finch beak breadth
Evolutionary and ecological time are the same
Eco-Evolutionary Dynamics
Shorter-term; changing allele frequencies within species or populations
Ex: beak depth in Galapagos finches
Microevolution
Longer-term; evolution above the level of species evolution of clades
Ex: Adaptive radiation
Macroevolution
Proposes that macroevolution is best described as long periods of stasis punctuated by rapid, cladogenesis, or the evolution on new clades. They propose this as an alternative to phyletic gradualism, the idea that evolutionary change proceeds smoothly at similar rates over time.
Theory of Punctuated Equilibria
Evolutionary change within clades
Anagenesis
The generation of two or more species from a common ancestor, in the absence of geographic isolation between descendants (disruptive selection)
Sympatric speciation
The generation of two or more species from a common ancestor, facilitated by complete geographic isolation between descendants, and often aided by reinforcement upon secondary contact (where hybrids do not do well which causes divergence and reproductive isolation).
Allopatric speciation
The diversification of a group of organisms into forms filling different ecological niches.
Ex: African rift lake cichlids
Adaptive radiation
What conditions favor adaptive radiation?
Sudden opening of new, unexploited ecological niches (especially on islands)
The evolution of novel traits that permit the exploitation of previously existing, but empty, niches
The presence of strong selection leading to phenotypic and genetic divergence across niches
The engine of adaptive radiation
Ecological speciation
What forces the evolution of the genome?
Mutations, recombination, genetic drift, selection, and intragenomic conflict
A to G or C to T
Transitions
A to C or G to T
Transversions
Increase in frequency of an allele due to it’s physical linkage with a
different allele that is under selection
Genetic hitchhiking
The number of differences in homologous sequences between clades
Substitution rate
The surprisingly low correspondence between the “complexity” of an organism and its genome size
C-Value Paradox
A gene gets copied and inserted into another place in the genome, eventually mutates to serve a new or modified function (or lose function completely to become a pseudogene). Can happen by several mechanisms, including retro transposition (mRNA is translated back to DNA and inserted back into the genome).
Gene duplication
Duplication, deletion, or incomplete retrotransposition
Chimeric genes
a transposon (chromosomal segment) whose sequence shows homology with that of a retrovirus.
Retrotransposon
Mutation(s) in non-coding, presumably “junk” DNA give rise to a new, functioning gene
De novo genes
Difference in sequence variation between clades is primarily due to selection acting to increase the frequency of beneficial mutations (positive selection or evolution of phenotypes(directional)) and decrease the frequency of deleterious mutations (purifying, or negative, selection or stabilizing selection or removal of deleterious things). Loss or gain of neutral mutations is seen as due primarily to their physical linkage with loci under positive or purifying selection.
Selectionist hypothesis
Differences in sequence variation between clades is primarily due to mutations that do not strongly affect organisms-level fitness (drift of genes that are neutral)
Neutralists hypothesis
Use of mutation rate to determine the timing of divergence between clades
Molecular clock
The ratio of non-synonymous to synonymous mutations in protein coding sequences
dN/dS ration
A nucleotide mutation that alters the amino acid sequence of a protein
Non-synonymous substitution
A change in the DNA sequence that codes for amino acids in a protein sequence, but does not change the encoded amino acid
Synonymous substitution
dN/dS >1
Positive selection
dN/dS <1
Negative selection
dN/dS=1
Neutral evolution
The relative high levels of genetic variation in neutral populations were (and still is) seen as evidence in support of the neutral theory, but…
Levels of genetic diversity are only weakly correlated with population size. Is often seen as strong evidence against the neutral theory
However, the more individuals in a population allows for more mutations and thus more genetic variation
Neutral Theory and the “Paradox of Variation”
