bio 002 quiz 2 (evolution)

evolution definition

change in proportions of heritable properties of groups of organisms over the course of generations

four forces of evolution

1. mutation

2. gene flow

3. genetic drift

4. selection

chromosomal inversion

change in chromosome structure

mutation definition

a physical change of genome (DNA)

somatic cells

NOT reproductive tissue (NOT PASSED DOWN)

germ line cells

reproductive tissue (PASSED to NEXT generation)

evolution by mutation definition

• change in proportion of physical traits by the physical change of genome

evolution by mutation other important info

• CANNOT cause a trait to spread

• RANDOM!!!

• creates raw diversity for other forces to act on

gene flow definition

transfer of genes, alleles, or traits from one population to another

• organisms move from one population to another (or gametes)

• change in proportion of traits in the local population

introgression

transfer of genetic material between different species of populations via hybridization followed by repeated backcrossing

genetic drift definition

any RANDOM process that affects who breeds, lives, or what genes/traits get passed down

• random fluctuations in allele (or trait) frequency

locus

location on a gene

what does genetic drift do a trait among populations?

• INCREASES genetic differences among populations

• DECREASES genetic variation within populations

• think of bell curve graph going out to the two ends

lost gene/trait

frequency of the trait/gene is 0 (left end of the two separated graphs)

• caused by genetic drift

fixed trait/allele

100% of the individuals in the population have the trait/allele

• caused by genetic drift

• right end of the two bell curves that separated

can alleles/traits change from being lost/fixed from genetic drift?

• NO they cannot change and are stuck

• … can change if you evoke another force of evolution

natural selection definition

• any consistent difference in fitness among phenotypically different individuals

• some individuals have more babies than others because of their traits

fitness definition

number of offspring produced in a lifetime

what force of evolution leads to adaptation?

natural selection

adapt (verb)

when a population undergoes evolution by natural selection and thereby becomes better matched to the environment

• individuals do NOT adapt

adaptation

an apparent match between a trait and its environment

adaptation (noun)

a trait that is matched to its environment

EVOLUTION by natural selection definition

• consistent relationship for that trait, between parents and offspring, which is partially independent of common environmental effects = INHERITANCE

• basic requirements

  • variation

  • consistent relationship between trait and number of offspring produced fitness differences

agent of selection definition

factor (thing) causing differences in fitness

target of selection definition

trait that is linked to fitness differences (horn length in lizard)

formula for strength of natural selection

mean (trait) of reproducing individuals - mean (trait) of entire population

• Xas - Xbs

viability selection

fitness component = survival

sexual selection

fitness component = number of gametes fertilized (number of mates copulated with)

• any consistent difference in # of gametes fertilized among phenotypically different traits

artificial selection

humans choose who lives and dies or who breeds based on their traits

heritability

how much of a trait, at the population level, is passed from parents to offspring

how much of the variance in a trait is due to heritable genetics

heritability graph

• dots are an avg of the family

• x axis = parent

• y axis = offspring

• slope of the line is heritability (h²)

what does the slope of the heritability graph represent?

• the heritability of the trait

• percentage of trait due to genetics (inherited) instead of environment

what is the breeders equation

equation that describes and predicts evolution by natural selection

• quantifies evolutionary change

breeders equation (formula)

R = h² * S

what is R in the breeders equation

change in the mean of trait across generations

(how much the mean changes from parents to offspring)

• evolutionary response

breeder’s equation “R” formula

x̄off - x̄bs

what does the S represent in the breeders equation

strength of selection

(change in trait value within a parental generation)

breeder’s equation S formula

x̄as - x̄bs

sexual selection definition

any consistent difference in the number of gametes fertilized among phenotypically different individuals

within sex competition

male x male competition

between sex choice

male and female choice

two parts of sexual selection

• within sex competition

• mate choice

Bateman gradient graph

• shows number of mates on x axis and number of offspring on y axis

• slope represents intensity of sexual seleciton

anisogamy hypothesis

there are differences in being male and female

• females fitness constrained by investment into making offspring (why they have a less steep slope)

• males will always experience stronger sexual selection

resource limitation hypothesis

differences in resource limitation dictate which sex gets a benefit from mating with more mates

• the sex least constrained (less limited) experiences stronger sexual selection

speciation

evolutionary process that causes one population to become two separately evolving groups that are reproductively isolated (they can no longer interbreed)

species

group of actually potentially interbreeding natural populations that are reproductively isolated from such other groups

allopatric speciation by vicariance

populations that have been separated for long periods should be more different than species separated later and would be less likely to mate

steps of allopatric speciation

1. a physical barrier forms that separates what was an interbreeding population

2. evolution occurs differently in the two new populations. different alleles and traits get fixed in the two populations

3. eventually so many differences accumulate that even when given the chance the two groups can no longer interbreed and produce viable offspring

how does selection impact speciation

SPEEDS UP

can fix traits or alleles if the environment is different for the two populations (causing them to be more different)

how does mutations impact speciation

SPEEDS UP

• new mutations could arise in one population but not the other

how does genetic drift impact speciation

SPEEDS UP

potentially a major force

fixes some alleles in one population and others in the other population

random, so different effects in different populations

how does gene flow impact speciation

SLOWS DOWN

mixing alleles of the two populations

prevents fixation and keeps the two populations similar

reproductive barriers

traits that have evolved while the two populations were separated that now hinder successful reproduction between the two populations

prezygotic barriers

hybrids have lower fitness than offspring from within species mating

causes populations to evolve behaviors (or other traits) that keep individuals from mating with individuals from the wrong species

prezygotic barrier examples

• temporal isolation

• behavioral isolation

temporal isolation

species breeds at different times (day, season, etc.)

behavioral isolation

elaborate behaviors (mating rituals) and species specific signals that prevent interbreeding between closely related populations

phylogeny

a visual representation of the evolutionary history of populations, genes, or species

reading a phylogenetic tree

• node represents the last shared common ancestor

• branches represent periods of stasis (no speciation)

• species on the end are the species alive today

• nodes can rotate and it doesn’t change the ancestors

“common descent”

• darwins idea

• graphing/labeling based on similar traits

• hypothetically more closely related to organism that is more similar to you

parsimony

• correct tree that is best supported by evidence

• tree that has fewest evolutionary events

convergent evolution

• when species that are not closely related evolve to have similar traits

• makes creating a phylogenetic tree harder