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Final Study Cards II - Flashcards

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Class:BIS 002B - Introduction to Biology
Subject:Biological Sciences
University:University of California - Davis
Term:Fall 2013
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selection response difference in trait mean between the unselected parents and the offspring 

What Darwin couldn't explain How does variation arise?
How are traits inherited?
What is the genetic basis of evolutionary change?

Assumption before Mendel my mid-19th century plant and animal breeders worked under a reasonable but incorrect assumption about inheritance: 
When you breed 2 different lines that differ for some trait(s), each of which is true-breeding, to produce hybrid offspring, these offspring all look pretty much alike, and often look like a mix of the two parental types. Thus there is blending inheritance. 

problem: eventually, the population should become phenotypically uniform, leaving no variation upon which selection can act

Law of Segregation When any individual produces gametes, the two copies of a gene separate/ segregate, so that each gamete receives only one copy 

thus from every parent of the p generation, every individual of the F1 generation receives one gene copy chosen randomly 

segregation during meiosis 

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Genetic definitions to know gamete, diploid/ haploid, chromosome, gene, locus, allele, homozygous/ heterozygous
dominant/ recessive

Mendel's 2nd law of heredity: Independent Assortment Mendel's next experiment 
crossing peas that different in 2 characters- seed shape and seed color 
this is a dihybrid cross

SSYY x ssyy

results in 4 possibilities 
Law of independent assortment Part 2 1. alleles of different genes assort independently during gamete formation if they are on different chromosomes 
that is chromosomes assort independently 
2. genes close together on the same chromosome are physically linked and generally do not assort independently 
when genes on the same are widely separated they may recombine so frequently that it appears as if they assort independently 
sex-linked genes hemophilia 
red-green color blindness
black/orange cat coat color
notice there are  no alleles on the Y
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pleiotropy allelic variation at one locus affects multiple traits

pigmentation and hearing: 40% of blue-eyed cats are deaf 

epistasis
gene x environment interaction temperature dependent tyrosinase allele
expression of phenylketonuria mutations
depends upon dietary phenylalanine 

population an interbreeding group of the organisms of the same species 

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relative fitness differential survival and reproduction relative to other members of the population 

Hardy-Weinberg Equilibrium in diploid organisms, genotype frequencies reach an equilibrium after one generation of random mating and both genotype and allele frequencies remain constant in subsequent generations. 
Assuming: large population, random mating, no gene flow from other populations, no new mutations, no natural selection 
a null hypothesis about expected allelic and genotypic frequencies in a population

How will populations evolve when Hardy-Weinberg assumptions are violated? genetic drift (sampling error in small populations)
non-random mating ( inbreeding, outbreeding)
gene flow between populations
new mutation (relatively unlikely explanation)
Natural Selection

Genetic Drift chance changes in allelic frequencies due to random sampling from generation to generation 
drift happens in all populations but its effects are more important in small populations 
2 demographic processes that can cause major evolutionary change through drift: 
founder effects in new populations
genetic bottlenecks when population size is reduced

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population bottlenecks population bottlenecks are analogous to founder effects, but occur when populations are greatly reduced in size
bottlenecks almost always cause allelic frequencies to change from that in the pre-bottleneck population 
when populations remain small for multiple 5-10 generations the loss of allelic diversity may be extreme 
bottlenecks occur when species are overharvested or when their habitats are reduced or fragmented extensively 

positive assortative mating when individuals mate with the same genotype as themselves
causes homozygote frequency to be higher than expected at H-W eq
negative assortative mating or disassortative mating when individuals stop mating with similar genotypes or close relatives

increases heterozygosity 

gene flow results from the migration of individuals and gametes (or other propagules like seeds and larvae) from one population to another, and the incorporation (by successful breeding) of the genes they carry into the novel gene pools 

larvae allow gene flow over thousands of km even if the adults barely move

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mutation a source of new alleles
most are deleterious or neutral, some may be beneficial 
an initially rare mutation may increase in frequency if it is beneficial but neutral or deleterious mutations may also be fixed in small populations through genetic drift
the rate of mutation at any locus is very low so it an unlikely cause for deviation from HW
but mutation produces new variation for selection to act upon

intrasexual direct competition among males for access to females 
weapons 
signals of fighting ability 
intersexual indirect competition among males to attract females
involves female choice

direct benefits of choosiness access to the male's territory
male parental investment
protection 
help in raising offspring 
avoidance of parasites (directly transmitted parasites, like STDs and lice)
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constraints on evolution can't change the law of physics
evolutionary history contraints possible developmental programs- you have to work with what you've got
tradeoffs- can't have it all
genetic variation- if it isn't heritable, it can't evolve

law of constant final yield intraspecific competition leads to more smaller plants or fewer larger plants 
in terrestrial habitats this limiting resource is often Nitrogen
in lakes and marine systems this limiting resource is often phosphorous 

when intraspecific competition is high decreased reproductive efforts of adults 
decreased survivorship and fledgling of young
decreased adult survivorship 
behavioral changes
increased dispersal (emigration), increased territorial defense, increased conflict, fratricide/ cannibalism

how do predators and prey coexist small r, slow response, cyclic populations 
alternative food sources 
refugia where prey can hide from predators
frequency dependent natural selection 
external control of herbivores or predators

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exploitative resource depletion
what one individual uses another cannot 
individuals need not encounter one another to compete
competition for food or nutrients

interference competitors confront each other and harass, chase, or otherwise prohibit other from using resources. 
competition for space
territoriality

apparent competition two prey of one predator compete 
competitive exclusion principle two species that use the same resource in the same way cannot coexist 
one will drive the other to extinction

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spatial structure key in preventing competitive exclusion
different species specialize in different habitats 
different physiological tolerances

temporal variability key in preventing competitive exclusion
different species specialize in different conditions and these conditions vary in time
physiological tolerances
behaviors

niche differentiation use of different resources within the same habitat at the same time

non-equilibrium systems-disturbance maintained even if species are exactly the same, chance events will eventually lead to one excluding the other

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character displacement the process of evolution toward niche divergence as a result of interspecific competition
compare populations living in the same location as another species (sympatry) vs those living in an area without the other species (allopatry) 
species packing adding new species shrinks the niche width of all species. to compensate species often become more specialized and more efficient at using a narrower range of resources 

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 selection responsedifference in trait mean between the unselected parents and the offspring 

 What Darwin couldn't explainHow does variation arise?
How are traits inherited?
What is the genetic basis of evolutionary change?

 Assumption before Mendelmy mid-19th century plant and animal breeders worked under a reasonable but incorrect assumption about inheritance: 
When you breed 2 different lines that differ for some trait(s), each of which is true-breeding, to produce hybrid offspring, these offspring all look pretty much alike, and often look like a mix of the two parental types. Thus there is blending inheritance. 

problem: eventually, the population should become phenotypically uniform, leaving no variation upon which selection can act

 Law of SegregationWhen any individual produces gametes, the two copies of a gene separate/ segregate, so that each gamete receives only one copy 

thus from every parent of the p generation, every individual of the F1 generation receives one gene copy chosen randomly 

segregation during meiosis 

 Genetic definitions to knowgamete, diploid/ haploid, chromosome, gene, locus, allele, homozygous/ heterozygous
dominant/ recessive

 Mendel's 2nd law of heredity: Independent AssortmentMendel's next experiment 
crossing peas that different in 2 characters- seed shape and seed color 
this is a dihybrid cross

SSYY x ssyy

results in 4 possibilities 
 Law of independent assortment Part 21. alleles of different genes assort independently during gamete formation if they are on different chromosomes 
that is chromosomes assort independently 
2. genes close together on the same chromosome are physically linked and generally do not assort independently 
when genes on the same are widely separated they may recombine so frequently that it appears as if they assort independently 
 sex-linked geneshemophilia 
red-green color blindness
black/orange cat coat color
notice there are  no alleles on the Y
 pleiotropyallelic variation at one locus affects multiple traits

pigmentation and hearing: 40% of blue-eyed cats are deaf 

 epistasis 
 gene x environment interactiontemperature dependent tyrosinase allele
expression of phenylketonuria mutations
depends upon dietary phenylalanine 

 populationan interbreeding group of the organisms of the same species 

 relative fitnessdifferential survival and reproduction relative to other members of the population 

 Hardy-Weinberg Equilibriumin diploid organisms, genotype frequencies reach an equilibrium after one generation of random mating and both genotype and allele frequencies remain constant in subsequent generations. 
Assuming: large population, random mating, no gene flow from other populations, no new mutations, no natural selection 
a null hypothesis about expected allelic and genotypic frequencies in a population

 How will populations evolve when Hardy-Weinberg assumptions are violated?genetic drift (sampling error in small populations)
non-random mating ( inbreeding, outbreeding)
gene flow between populations
new mutation (relatively unlikely explanation)
Natural Selection

 Genetic Driftchance changes in allelic frequencies due to random sampling from generation to generation 
drift happens in all populations but its effects are more important in small populations 
2 demographic processes that can cause major evolutionary change through drift: 
founder effects in new populations
genetic bottlenecks when population size is reduced

 population bottleneckspopulation bottlenecks are analogous to founder effects, but occur when populations are greatly reduced in size
bottlenecks almost always cause allelic frequencies to change from that in the pre-bottleneck population 
when populations remain small for multiple 5-10 generations the loss of allelic diversity may be extreme 
bottlenecks occur when species are overharvested or when their habitats are reduced or fragmented extensively 

 positive assortative matingwhen individuals mate with the same genotype as themselves
causes homozygote frequency to be higher than expected at H-W eq
 negative assortative mating or disassortative matingwhen individuals stop mating with similar genotypes or close relatives

increases heterozygosity 

 gene flowresults from the migration of individuals and gametes (or other propagules like seeds and larvae) from one population to another, and the incorporation (by successful breeding) of the genes they carry into the novel gene pools 

larvae allow gene flow over thousands of km even if the adults barely move

 mutationa source of new alleles
most are deleterious or neutral, some may be beneficial 
an initially rare mutation may increase in frequency if it is beneficial but neutral or deleterious mutations may also be fixed in small populations through genetic drift
the rate of mutation at any locus is very low so it an unlikely cause for deviation from HW
but mutation produces new variation for selection to act upon

 intrasexualdirect competition among males for access to females 
weapons 
signals of fighting ability 
 intersexualindirect competition among males to attract females
involves female choice

 direct benefits of choosinessaccess to the male's territory
male parental investment
protection 
help in raising offspring 
avoidance of parasites (directly transmitted parasites, like STDs and lice)
 constraints on evolutioncan't change the law of physics
evolutionary history contraints possible developmental programs- you have to work with what you've got
tradeoffs- can't have it all
genetic variation- if it isn't heritable, it can't evolve

 law of constant final yieldintraspecific competition leads to more smaller plants or fewer larger plants 
in terrestrial habitats this limiting resource is often Nitrogen
in lakes and marine systems this limiting resource is often phosphorous 

 when intraspecific competition is highdecreased reproductive efforts of adults 
decreased survivorship and fledgling of young
decreased adult survivorship 
behavioral changes
increased dispersal (emigration), increased territorial defense, increased conflict, fratricide/ cannibalism

 how do predators and prey coexistsmall r, slow response, cyclic populations 
alternative food sources 
refugia where prey can hide from predators
frequency dependent natural selection 
external control of herbivores or predators

 exploitativeresource depletion
what one individual uses another cannot 
individuals need not encounter one another to compete
competition for food or nutrients

 interferencecompetitors confront each other and harass, chase, or otherwise prohibit other from using resources. 
competition for space
territoriality

 apparent competitiontwo prey of one predator compete 
 competitive exclusion principletwo species that use the same resource in the same way cannot coexist 
one will drive the other to extinction

 spatial structurekey in preventing competitive exclusion
different species specialize in different habitats 
different physiological tolerances

 temporal variabilitykey in preventing competitive exclusion
different species specialize in different conditions and these conditions vary in time
physiological tolerances
behaviors

 niche differentiationuse of different resources within the same habitat at the same time

 non-equilibrium systems-disturbance maintainedeven if species are exactly the same, chance events will eventually lead to one excluding the other

 character displacementthe process of evolution toward niche divergence as a result of interspecific competition
compare populations living in the same location as another species (sympatry) vs those living in an area without the other species (allopatry) 
 species packingadding new species shrinks the niche width of all species. to compensate species often become more specialized and more efficient at using a narrower range of resources 

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