bio exam 3

Evolution is

Change in genetic composition of populations overtime, driving the origin and extinction of species and diversification of life

Evolutionary theory is

Our understanding of how genetic changes in populations through generations come to be, helps us form testable hypothesis

Erasmus Darwin vs Charles Darwin

Erasmus suggested evolution, but didn't know the mechanism

Jean- Baptiste Lamarck proposed

A potential mechanism of evolution, inheritance of acquiredCharacteristics

Lyell'S principles of geology suggested that

Forces we see today are also responsible for events in the past and cause geological features of earth

MalthuS's an essay on the principle of population suggests that

Populations have potential for exponential increase, but are kept in check by limited food resources

Artificial selection

Humans intentionally breed certain species

Darwin's great insight

Individuals that fit the environment better will be more likely to survive and reproduce

Descent with modification means

Divergent species share a common ancestor

Darwin's 3 conditions for natural selection

Variation in a trait, variation must be heritable, some variants must have higher fitness than others

If Darwins 3 conditions for natural selection are met

Then there will be an increase in the frequency of that trait in the next generation

The closest living relative to whales is the

Hippopotamus

The origin of genetic variation is

Mutation

Mutations occur

Randomly, no consideration for an organism's needs

Natural selection works by

Acting on random mutations, helpful ones survive, harmful ones don't

Selection is

A non-random process of evolution that favors individuals that survive and reproduce

Fitness is

The relative contribution of an individual to the gene pool of the next generation

Fitness is measured by

Relative number of offspring that survive and reproduce

Deleterious mutations are

Harmful

Shifts in allele frequencies indicate that

A selection process is taking place

Adaptation is

A favored trait that evolves through natural selection, also theProcess that produces that trait

Qualitative traits are

Usually influenced by few loci, discrete phenotypic characters

Quantitative traits are

Usually influenced by larger group of genus, continuous variation

Total phenotypic variance is made up of

Genetic variance and environmental variance

Heritability is

The proportion of total phenotypic variance that is due to measurable genetic factors

How to calculate heritability (h squared )

Genetic variation divided by total phenotypic variation

Phenotypic plasticity is

When a trait responds to its environment

When h2 is close to 1

Most phenotypic variation is due to genetics

Heritability is measured by

Parent-offspring regression (trait of parent vs trait of offspring)

Natural selection is a - of evolution

Mechanism

Evolutionary processes (5)

Mutation, selection, gene flow, genetic drift, nonrandom mating

Gene flow is

The migration of individuals between populations, changing allele frequencies

Genetic drift is

An effect of random variation in which alleles get passed to offspring leading to fixation and decreased genetic diversity

Fixation is

When one allele is the only available option In a gene pool at a time

Unless counteracted , Genetic drift will result in

Fixation

_ Populations are more vulnerable to genetic drift

Small

Population bottleneck is

An environmental event that results In survival of only a few individuals, loss of genetic diversity

Founder effect is

When a few individuals from a population colonize a new area and become isolated, decreased genetic diversity

An alleles probability of fixation due to genetic drift is equal to

Its frequency at and point

The larger the population, the more generations it takes for an allele to

Drift to fixation or be lost

In a noninfinant Population, genetic drift will eventually

Remove all but one allele (disregarding mutation, selection, and migration)

Drift acts mostly on what variation

Neutral or nearly neutral

Selection acts on what variation

Beneficial and deleterious

Directional selection is

When individuals at one extreme of a trait distribution have higher fitness, change In mean, might change variance

Stabilizing selection is

When individuals near the middle of a trait distribution have higher fitness, reduces variance, mean does not change

Disruptive selection is

When individuals at both extremes of a character distribution have the highest fitness, increased variation, bimodal distribution

Heterozygote advantage is

When individuals with 2 different alleles for a gene have greater fitness than homozygotes

Negative frequency dependent selection is

Multiple phenotypes have similar fitness, maintains genetic diversity, phenotypes have higher fitness when rare

Positive frequency dependent selection is

When common phenotypes have more fitness than rare phenotypes

Sexual dimorphism is

When elaborate traits are present In only one sex, male or female, usually ones that attract predators

Sexual selection is

When an organism's phenotype influences its mating success

Intrasexual selection is

Competition within a sex for access to mates

Intersexual selection is

Choices among phenotypes in potential mates

Anisogamy is

Unequal sized gametes, females typically have greater investment In reproduction

What is a direct benefit to females

Gifts that help the female herself survive

What is indirect benefit to females

Good genes for her offspring

Assortative mating is

A type of non-random mating when individuals prefer others of the same phenotype

Disassortative mating

When individuals prefer others of different phenotypes (inbreeding avoidance)

Habitat selection is

When more frequent matings occur between individuals with similar habitat preference

Population genetics is

The study of genetic structure (allele and genotype frequencies in a population) and how it changes in response to evolutionary forces

Gene pool is

The set of genetic information (alleles and genes) within a population

The size of the gene pool equals

Total number of alleles

Allele frequency is the

Number of each allele for a gene in a population divided by total number of all alleles for that gene in a population

Genotype frequency is

Number of individuals with each genotype in a population divided by total number of individuals In a population

For every population, the frequencies of all alleles sum to

One

Monomorphic is

When only one allele is at a given locus, fixed

Polymorphic is

When there is more than 1 allele for a given gene

How to find the Frequency of A allele

P= 2N AA plus N Aa divided by 2n

Genotype frequency of AA

NAA /n

At hardy-weinberg equilibrium, allele and genotype frequencies

Do not change (no evolution)

Conditions for hardy-weinberg equilibrium

No mutation, no selection, random mating, no gene flow, no genetic drift (infinite population)

Allele frequency predictions at hardy Weinberg equilibrium

P squared, q square, 2pq

Nucleotide substitution (point mutation) is

A change in one nucleotide in a gene sequence , canbe Synonymus or nonsynomymus

Substitution rates are highest at

Positions that do not change the amino acid being expressed

If synonymus and nonsynonymus substitution rates are similar

The corresponding amino acid is likely under neutral selection

If nonsynonymus substitution exceeds synonymus

The corresponding amino acid is likely under positive selection

If synonymus substitutions exceed nonsynonymus

Corresponding amino acids are likely under purifying selection

Neutral theory is

The concept that most variants in populations are selectively neutral

Rate of fixation of neutral mutations is

The probability that a new mutation will be fixed by drift globe

Number of new mutants in a population per generation equals

2N times neutral mutation rate

The rate of evolution caused by mutation and drift is relatively

Constant

Number of nucleotide changes can be used as a

Molecular clock, to calculate evolutionary divergence times between species

Genome sizes vary due to

Differences in amount of non-coding DNA

Genomes are measured in

Base pairs ( one rung on the DNA ladder)

The lower percent of genome encoding functional genes,

The greater the genome size

Non coding DNA may still

Alter the expression of surrounding genes or develop novel functions

Amount of noncoding DNA may be related to

Population size

Noncoding sequences that are deleterious are likely to be purged by selection in

Large population bc lack of vulnerability to genetic drift

The rate of fixation of neutral mutations is equal to

Rate of new neutral mutations

Human genome has how many base pairs and genes

3 billion, 22,000

What percent of human DNA are protein coding sequences

3%

If only protein and RNA coding portion of genomes are considered there is less

Variation in genome size

Large populations are more efficient at removing

Harmful noncoding DNA, which is why there's usually less in large populations

Disadvantages of sexual reproduction are

The twofold cost of sex - cost of meiosis and cost of males

Cost of meiosis is

The fact that only 50% of the female's genes are passed on to offspring

Cost of males is

The division of offspring into genders (males) reduces a female's overall reproductive rate

Parthenogenetic means

Asexual

Asexual mutants can arise in sexual-reproducing populations, leading to increased

Fitness

Advantages of sexual reproduction

Elimination of deleterious mutations through recombination and selection, genetic diversity which can defend against pathogens, and repairs DNA damage.

Genetic load or Muller'S ratchet is

The concept that asexually reproducing lineages can't remove harmful mutations until the lineage dies out