Exam One Prep Flashcards
What is the difference between homologous and analogous structures?
Ancestry, homologous structures are structures that are shared from a shared ancestor whereas analogous structures are similar structures with no common ancestor.
microevolution
allele frequency changes within species over relatively short time
speciation
species lineages split to form new species
macroevolution
large evolutionary changes above species level, taking place over much longer periods of times
what are the 6 evidences for evolution
- fossils
- homology
- biogeography
- direct observation
- selective breeding
- vestigal traits
creationism
the belief that the universe and living organisms originate from specific acts of divine creation, as in the biblical account, rather than by natural processes such as evolution
fossil
any trace of an organism that lived in the past
transitional fossils
fossils that show intermediate states between and ancestral trait and that of their descendants
an example with would be an archaepteryx, demonstrating modern feathers and a dinosaur like skeleton
homology
similarity resulting from inheritance of traits from a common ancestor
homologous structure
traits derived from a common ancestor
forelimbs of horses, dolphins and humans
analogous structure
organisms with similar traits but evolved independently
spikes in porcupines and spikes in a pine tree
developmental homology
embryos from different vertebrates showing similarities
molecular homology
the nucleotide triplets (codons), universal genetic code demonstrating all life forms are related through common ancestry
biogeography
geographic distribution of species on Earth
organisms that live in the same regions are often related
examples would be the hawaiian honeycreepers and marsupials
direct observation examples
evolution of antibiotic resistant bacteria, insectiside resistance, industrial melanism ( peppered moth), covid-19
selective breeding
also known as artificial selection
selecting mating partners by looking for various traits
domestication of corn
vestigial traits
structured that derived from ancestor, no longer in use but present in reduced form
human tailbone, human arrector pili (goosebumps)
malthusian dilemma
population when unchecked, increases exponentially and resources are outnumbered
darwin’s interpretation of malthusian dilemma
species tend to produce more offspring than the enviornment can support, causing competition for those resources
theory of catastrophism
earth was 6000 years oldd, living organisms on the planet were created after the great flood
doctrine of uniformitarianism
geological processes that are going on today worked similarly in the past
(understanding history by examining this process and working backwards ?)
Lamarck’s theory
transmutation of species and inheritance of aquired characteristics
transmutation of species
organisms driven to greater complexity
adapting to enviornment and more complex to transform into another species
inheritiance of aquired characteristics
change through use and disuse- characteristics of an organism develop during its lifetime in a response to enviornment and then passed down to offspring
common example is a giraffe stretching its neck to make it longer and passing that trait of a longer neck down to its offspring
darwin’s theory
natural selection- those with any change variation that provides advantage will tend to be preserved
darwin’s four postulates
- principle of variation
- principle of heredity
- more offspring are produced than can survive
- survival and reproduction are not random
epigenetics
heritiable changes that do not change DNA sequences
ex: stressed male rodents were able to pass on signs of traumas through their sperm RNA
principle of variation
within a population there is a variety of traits
principle of heredity
offspring tend to inherit their parents’ characteristics
genotype
genetic makeup of a morphological trait
ex: BB, Bb, and bb
phenotype
an observed trait, expression of a genotype
ex: flower color
alleles
variant form of the same gene that share the same locus on chromosome
ex: B and b
Four Forces of Evolution
- mutation
- genetic drift
- gene flow (migration)
- natural selection
changes allele frequencies in a population
population
a group of individuals of the same species that have a higher change to mate among themselves than individuals from another group
point mutations
a single DNA nucelotide that is inserted, deleted, or changed
create new alleles at a genetic locus
ex: sickle cell anemia, color blindness, monarch butterfly resistance to milkweed
effects of point mutations on protein function
- synonymous mutations
- nonsynonymous mutations (missense or nonsense)
mutations caused by changes in DNA sequence
synonymous mutation
changes in DNA sequence that do not change the amino acid sequence
also known as silent mutation
probably neutral with regard to natural selection
nonsynonymous mutation
changes in DNA sequence that change the amino acid sequence of a protein
two kinds: nonsense and missense
nonsense mutation
a codon is changed to a stop codon
missense mutation
codon is changed for a codon that codes for a different amino acid
chromosome inversion
segment of chromosome is inverted
may not change the genetic information, but the order of genes changed
types: paracentric and pericentric
paracentric inversion
inversion that doesn’t include centromere
pericentric inversion
inversion includes centromere
easily identifiable through karyotyping
what does chromosome inversion often cause?
A. significant gain in DNA.
B. significant loss in DNA.
C. creation of nonfunctional pseudogenes.
D. suppression of recombination.
D. supression of recombination
reduces crossing over within inverted regions and increases it in others
inversion heterozygote
one set of chromosomes with normal gene sequence, the other set has inverted gene sequence
rarely produces recombinant gametes
gene duplication
a region of DNA is duplicated
mechanisms of gene duplication
- unequal crossing over during meiosis
- retrostransposition
- whole-genome duplication
unequal crossing over during meiosis
homologous chromosomes misaligned at the prophase stage of meiosis l
results in gene duplication in one chromosome and deletion in the other
retrotransposition
instead of being translated into proteins they are reverse transcribed into DNA sequence
ex: chondrodysplasia in dogs
retrotransposons
mobile genetic elements that can cause insertion mutations and gene duplication
also known as jumping genes
whole genone duplication
entire set of chromosomes is duplicated
nondisjunction
homologous chromosomes or sister chromatids fail to separate during cell division
polyploidization
nondisjustion causes this: common in plants that self fertilize, prevents offspring from interbreeding with parent species
different # of chromosomes comapred to parent species (typically double)
common source of speciation in plants
Which of the following statements is not true?
A. Duplicate genes usually take on new functions.
B. Chromosome inversion does not cause gene duplication.
C. Whole-genome duplication may cause speciation.
D. Human globin gene family is an example of gene duplication.
A. Duplicate genes usually take on new functions.
genetic variation
genetic differences found in indivudals or populations
measured genetic variation by polymorphism and heterozygosity
polymorphism (P)
estimate of loci that are polymorphic
high polymorphism = high genetic variabillity
polymorphic locus: the most common allele is no more than 95%
heterozygosity (H)
% or fraction of loci that are heterozygous
can be applied to individual or population
high heterozygosity = high genetic variation
genetic load
natural selection is very ineffective at removing rare recessive deleterious alleles from a population
in short- unfavorable alleles
sex-linked traits
generally is a trait that occurs on the X chromosome
genotype frequency of x-linked traits in males = allele frequency
h-w is then applied differently for these traits
what does hardy-weinberg equilibrium demonstrate?
what is its use?
evolution won’t occur in a population if its five conditions are met
provides an estimate of expected allele frequency assuming no evolution
hardy-weinberg equations
p+q=1
p^2+2pq+q^2=1
p^2 is frequency of homozygous dominant
2pq is frequency of heterozygous
q^2 is frequency of homozygous recessive
If population meet all HWE assumptions which of the statements is true?
A. The population will evolve way more slowly than normal.
B. The population does not evolve as long as these conditions
hold.
C. Dominant alleles in the population’s gene pool will slowly
increase in frequency while recessive alleles will decrease.
D. The population has an equal frequency of dominant and
recessive alleles.
B. The population does not evolve as long as these conditions
hold.
Five conditions for HWE
- No mutation
- No genetic drift (i.e. infinitely large population)
- Random mating
- No migration (no gene flow)
- No selection
these are essentially the driving forces of evolution MINUS RANDOM MATING
Why is nonrandom mating not a source of evolution?
Nonrandom mating changes genotype frequency, but there is no change to allele frequency
natural selection
surrival and reproductive success due to differences in phenotype
occurs as a result of individual differences in fitness
causes adaptation
adaptation
how individuals better fitted to surrvive in their enviroment
three main kinds: structural, physiological and behavioral
fitness
avg # of offspring of a individual with a certain genotype compared to that of another
usually abreviated as
a measure of the contribution of a genotype to the gene pool of the next generation
darwin described this as the abillity to survive, find mate and reproduce
general selection model (GSM)
predicts changes in allele freq. from one gen to the next due to natural selection
w=1
genotype with highest fitness and highest reproductive success
w<1 (fitness of other genotypes will be less than 1)
selection coeffcient (S)
measure of the relative strength of selection acting against a genotype
can be thought of as the reduction in fitness
fitness and selection coefficient equation
s+w=1 or s=1-w
5 general models of natural selection
- selection against recessive allele
- selection against dominant allele
- heterozygote had intermediate fitness
- heterozygous advantage
- selection against heterozygote
general model #1:
selection against recessive allele
what happens to the alleles?
AA: 1
Aa:1
aa: 1-s
Allele A will be the most common but will not be fixed and by the only one
frequency of allele a will be low but it will not reach 0
General Model #2
Selection against dominant allele
AA: 1-s
Aa:1-s
aa: 1
allele a will be fixed at this locus
allele A will be removed from the population
General Model #3: directional
Heterozygote has Intermediate Fitness
AA: 1-s
Aa:1-s/2
aa: 1
(selection for allele a & removes allele A from pop. )
OR
AA: 1
Aa:1-s/2
aa: 1-s
(selection for allele A & removes allele a from pop.)
changes in p and q will be slower
allele that is favored by selection will be fixed, allele A will be fixed
General Model #4:
Heterozygote Advantage
AA: 1-s
Aa:1
aa: 1- t
t is selection coefficient like s
there are several names for this, heterosis, overdominance
leads to stable polymorphism BOTH alleles remain in population
Model of Selection #5
Selection Against Heterozygote
(“Underdominance”)
AA: 1-
Aa:1-s
aa: 1- s
leads to disruptive selection, equilibirum is UNSTABLE
whichever allele is at highest frequency will likely become fixed
polymorphism is NOT maintained
Frequency dependent selection
the fitness of a genotype of allele is affected by its frequency in the population
postive frequency dependent selection
allele or genotype enjoys higher fitness when it is common
a rare allele will be at a selective disadvantage and CANNOT maintain polymorphism
negative frequency dependent selection
allele or genotype enjoys higher fitness when it is rare
a rare allele will have an advantage leading to stable polymorphism
ex: scale eating fish, right and left handed fish
gene flow (migration)
movement of alleles among populations (movement of individuals)
**homogenizes genetic differences and keeps popualtions similar to each other **
what are the factors that affect gene flow?
- vagility
- distance
- barrier
vagility
the abillity to move
higher vagility higher gene flow
distance
between different populations
greater distance, lower gene flow
barrier
geographical isolation that prevents movements of individuals
stronger barrier, lower gene flow
outbreeding depression
cross between genetically distinct groups may produce offspring with lower fitness
ex: apline ibex capra ibex- hybrids between the two birthed calves too early causing the entire population to disappear
relationship between gene flow and genetic drift?
gene flow and genetic drift have opposite effects
extinction vortex
small populations become increasingly vunerable toward extinction
genetic drift
random change of allele frequencies over generations due to change or “sampling error”
results in LOSS of genetic variation, effects are strongest in small populations
types of genetic drift
bottleneck and founder effect
bottleneck effect
caused by catastrophic effect that greatly reduces population size
ex: australia bushfires 2019-2020
whooping cranes- hunted nearly to extinction, from 6 mitochondrial types, there are now only 1
founder effect
caused by ecological seperation through migration from orginal population
in simpler terms, small group break off and make new population
allele frequencies of new population will differ than that of the source pop.
effective population size (Ne)
effect of genetic drift is determined by this
influenced by the mating system (breeding ratio)
polygyny
males mate with multiple females
polyandry
females mate with multiple males
effective population size equation
Ne = (4 * Nm * Nf) / (Nm + Nf)
Nm = number of breeding males
Nf= number of breeding females
factors influencing Ne
- influenced by the mating system (breeding ratio)
- fluctuation census population size over time (bottlenecks lower Ne)
- variation in family sizes ( if some families have many more offspring, lower Ne)
- sex ratio (unequak sex ratio lowers Ne)
types of nonrandom mating
- negative assortive mating
- positive assortive mating
negative assortive mating
mates between DIFFERENT phenotpes
progressive incr. in the # of HETEROzygotes
positive assortive mating
mates between similar phenotypes
progressive incr. in the # of HOMOzygotes
inbreeding
mating among close relatives, increases homozygosity at all loci
(type of positive assortive mating)
self-pollination in plants
extreme forms of positive assortive mating and inbreeding
what happens to allele frequencies in nonrandom mating
NOTHING
p and q remain the same
inbreeding depression
reduced fitness due to inbreeding
increased homozygosity, expression of deleterious recessive alleles
ex: greater prarie chicken in illinois
florida panther
genetic load
collection of deleterious recessive alleles
genetic rescue
augment gene flow into small populations to reduce inbreeding depression
successful cases- greater prarie chicken, florida panther
unsucccessful- outbreeding depression in alpine ibex
quantitative genetics
looks at the evolution of multilocus traits that show continuous variation
quantitative traits
product of both genotype and enviornment
has continuous variation, typically are controlled by multiple genes
ex: morphology (size and shape)
physiology ( pressure, temperature)
performance ( speed, puzzle solving)
fitness ( seeds, suriviving offsrping)
multilocus trait
combination of alleles found at two or more loci in a single individual
hertiable variation- individual level phenotype equation
Phenotype(P) = genotypic effects (G) + enviornmental effects (E)
for the single locus traits enviornmental effects E= 0
Phenotype equation (other ver. )
Vp= Vg + Ve
Vp = phenotypic variance
Vg = genetic variance
Ve = environmental variance.
heritabillity (h^2)
proportion of the variance in phenotype that is transmissible from parents to offspring
influenced by genetic, ranges between 0 and 1, one being that the only influence is genetics
can be used to predict changes in the population as a result of natural selection
