Chapter 23 Flashcards
what 4 processes drive evolution
- natural selection
- genetic drift
- gene flow
- mutation
how does natural selection drive evolution
increases frequency of certain alleles
how does genetic drift drive evolution
allele frequencies change randomly
how does gene flow drive evolution
individuals leave one population, join another, and breed; introduce different alleles
how does mutation drive evolution
modifies allele frequencies by continually introducing new alleles
what did Hardy and Weinberg calculate
what would happen if pairs of gametes are plucked at random out of a gene pool and then form offspring
do allele frequencies change over time
NO
what does a null hypothesis specify
what should be observed if hypothesis being tested is NOT correct
what does nonrandom mating cause
only genotype frequencies to change, not allele frequencies unless it occurs with other processes
what does inbreeding lead to
- increase in homozygosity of population
- leads to decrease in average fitness via selection
what is the most extreme form of inbreeding
self fertilization
does inbreeding cause evolution
no because allele frequencies do not change in population as a whole
how does inbreeding influence evolution
increases the rate at which natural selection eliminates recessive deleterious alleles from a population
- speed up rate of evolutionary change
when does nonrandom mating occur due to sexual selection
occurs sometimes because an organism actively choses a certain mate based on it’s physical and/or behavioral traits
what does natural selection violate
assumptions of Hardy-Weinberg
what combines to cause natural selection
ecological selection + sexual selection
what are the 4 main patterns of natural selection
- directional
- stabilizing
- disruptive
- balancing
when is genetic drift random
in respect to fitness- changes in allele frequency that it produces are not adaptive
when is genetic drift most pronounced
in small populations
over time, what can genetic drift lead to
random loss or fixation of alleles
- genetic variation then decreases
what causes genetic drift in natural populations
founder effect and bottleneck effect
what outcomes can genetic drift cause on fitness
increase, decrease, or same
what causes gene flow
when individual leaves one population, joins another, and breeds
is gene flow random
with respect to fitness, yes
what ways can mutation occur
- point mutation
- chromosome level mutation
- lateral gene transfer
is mutation fast or slow
slow
when can mutation have a large effect on evolution
when combined with genetic drift, gene flow, and selection
mutation in evolution
- mutation is ultimate source of genetic variation
- mutations are random with respect to fitness
- if mutation did not occur, evolution would eventually stop
- mutation alone is usually inconsequential in changing allele frequencies at a particular genre
what reduces differences between populations
gene flow
what causes populations to diverge
- natural selection
- genetic drift
- mutation
what is genetic drift caused by
sampling error
what are the causes of a bottleneck effect
- disease outbreak
- natural catastrophes
- human catastrophes
what occurs in disruptive selection
- competition
- abiotic or biotic
- eventually lead to different species
- increase variation in trait
what occurs in balancing selection
maintains “status quo”
inter sexual selection involves who in a species
between different sex’s
- male showing off for female
- make and female usually look different
intra sexual selection involves who
within a sex
- competition for mate
- shift in features that allow for better chance to win competiton
directional
favors one extreme, shifting the population traits
stabilizing
favors average traits, reducing variability
