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Evolutionary Bio Exam III
from lecture slides
Terms in this set (70)
the repair hypothesis:
Recombination evolved because it necessary for DNA repair.
True or False: If you can repair your DNA, you have a much higher fitness
Red Queen Hypothesis
each species has to run (evolve) as fast as possible just to stay in place -- because predators, competitors, and parasites also continue to evolve
Examples of "diseases" as adaptations:
Sickle Cell Anemia
Why are 50:50 sex ratios so common?
As the number of daughters increase in a population,
large fitness gains to those producing (the now more rare) males
Selection favors more sons
What is another way that sex ratios are altered?
environmental modulation (as opposed to genetic modulation)
e.g. the rate of male births in turtles and lizards is affected by temperature.
What effect does climate change have on populations with environmentally modulated sex ratios?
Global increase in temp could lead to skewered sex ratios, and species could potentially wind up all one sex.
for example, American alligators produce all females if the temp is <30 degrees Celcius
Define inclusive fitness
describes the fitness of all of your relatives, including you.
Define sexual selection
the kind of natural selection causing the evolution of traits that INCREASE reproductive fitness
Origin of sexual selection according to Darwin?
anisogamy (fusion of two gametes), but it affects both sexes
leads to competition between males
Define Operational Sex Ratios
the ratio of sexually competing males to sexually competing females.
Why are females so choosey (mating-wise)
more elaborate signals suggest stronger fitness levels aka sexy son/good genes hypothesis
What is the handicap principle?
A consequence of the good genes theory where by males with the most exaggerated traits indicate their good genes by having overcome the cost (or handicap) of such extraordinary secondary sex characteristics. Also known as the honest indicator principle.
True or False: mate choice increases a component of offspring fitness in fruit flies
If you're allowed to choose your offspring, odds are that fitness levels increase.
Define Antagonistic Coevolution
the relationship between males and females where sexual morphology changes over time to counteract the opposite's sex traits to achieve the maximum reproductive success
With all of other things being equal, males benefit more from frequent mating because sperm is cheap energy-wise
Females re-mating decrease fitness levels
True or False:
In sexual selection, Losses >> Gain
This suggests that there are RAPID evolution of male traits that females want
sensory bias is
sensory bias - females have innate preferences, even for traits that males don't have
Darwin believed that species are a _______ ___________ imposed on biological variation.
species represent a _______ in the evolutionary process
list five ways species can be defined by
1. morphology (taxonomy)
5. phylogenetic inference
species are those that when interbred, cannot produce a fertile offspring (Wallace)
What is the biological species concept? (Mayr)
species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups
Points about Biological Species Concept:
- reproductive isolation defines species.
- BSC does NOT apply to asexually reproducing species
- Infrequent interbreeding or gene exchange in nature is implied
Is hybridization a challenge to the biological species concept?
yes, due to stable hybrid zones (genetic exchange between species)
What 3 things determine the fate of genetic exchange?
Dispersal (gene flow)
the movement of a gene (gene flow) from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species
What is the Recognition Species Concept? AKA reproductive species system
a concept of species, according to which a species is a set of organisms that recognize one another as potential mates: they have a shared mate recognition system
Recognition Species concept says that ____________________
species may exist as groups without relation to other groups
phylogenetic species concept
defines a species as the smallest group of individuals on a phylogenetic tree
species are (more or less) lineages through time
Genotypic cluster species concept
Species are distinct genetic clusters, separated by few or no intermediates
traits that prevent interbreeding and maintain reproductive isolation
Two kinds of reproductive isolation
Five prezygotic isolating mechanisms
2. Ethological (Behavioral)
4. Gametic Isolation
5. Mechanical Isolation
If in the offspring of two different animal species one sex is absent, rare, or sterile...
that sex is the heterogametic sex
example - Mules
- Disharmonious interactions between the different genes inherited from the two parents (epistasis)
In the ancestral population, the genotype is AA BB. When the population is split into two, A evolves into a in one population and B evolves into b in the other. a and b are mutually incompatible
extrinsic postmating isolation
•Diverged populations or species are adapted to different environments
lower fitness, behavior is different and cannot find mates
geographic variation + ISOLATION + adaptation =
population isolated by geologic process
Natural selection cannot strengthen intrinsic postzygotic isolation
when two groups of the same species live in the same geographic location, but they evolve differently until they can no longer interbreed and are considered different species
"instant speciation" duplication of the entire set of chromosomes
Founder Event Speciation
small group leaves population to new area with varying gene frequency
A hypothesis for speciation, in which genetic change is enhanced in populations that grow rapidly ("flush") after being founded by a few individuals.
genetic analysis of complex characteristics
How is Francis Galton relevant to quant. genetics?
believed he could best understand genetics by studying resemblance between relatives by regression
quantitative traits are influenced by ____________ and the ______________
List the 3 Quant. Genetics observations/objectives in notes
1. goal is to predict the effectiveness of kinds of artificial selection
2. to understand the ways genes combine their effects while a population undergoes natural selection
3. shows the tendency for relatives to resemble each other in metric characters.
in Quant. genetics:
___ # of phenotypes demonstrates complete dominance
___# of phenotypes demonstrates no dominance
a gene at one locus alters the phenotypic expression of a gene at a second locus
Pleiotropy is used to describe a single gene that affects several phenotypes.
additive genetic variation
the proportion of genetic variation that is due to differences among alleles that sum together (no dominance)
Define phenotypic plasticity
the ability of one genotype to produce more than one phenotype when exposed to different environments
genotype ----> gamete ----> genotype
results in gene expression (___________) are dependent on the underlying genes (____________) and the environment
Vg/Ve = __________
Heritability in the broad sense
Va/Vp = _______
heritability in the narrow sense
stochastic(random) variation >>>> other sources of variation
most cases of cancer are from __________
mutations aka DNA replication errors.
What is linkage disequilibrium?
non-random association of alleles at different loci
Vp = Vg + Ve + Vge
phenotypic variance equation
why might recombination be advantageous?
introduces new variants of chromosomes and therefore increases population variation
describes the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner
process by which a favorable mutation becomes fixed
The process by which a neutral or even disadvantageous allele is able to "ride along" with a nearby favorable allele to which it is physically linked, and thus increase in frequency.
what is the answer to mullers ratchet?
it gets rid of the deleterious mutations that asexual organisms cant
paradox of sexuality
cost of males
About half of the resources is allocated to producing otherwise "useless" males in sexual reproduction when compared with asexual reproduction. It is also the main concern in unraveling the enigma of sex.
Asexual reproduction in which females produce offspring from unfertilized eggs.
asexual during the good times (quick repopulating)
sexual before high mortality/intense selection
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