Evolution of Populations Flashcards
What is a genotype?
set of genetics; which chromosome are there
What is phenotype?
physical apperance
What does homozygous mean?
same alleles (?); AA or aa
What does heterozygous mean?
different alleles (?); Aa
What is the Hardy-Weinberg Prinicple?
the original proportions of the genotypes in a population will remain constant from generation to generation as long as 5 assumptions are met (no evolution is occurring)
What 5 assumptions must be met for the Hardy-Weinberg Principle?
no mutation, no gene flow, random mating, large population size, no natural selection
What does gene flow mean?
flow of genetics between 2 different populations; individual gametes move from one population to another
What does random mating mean?
random, no choice
What is large population size important for hardy-weinberg principle?
if small population, inbreeding could occur
What are populations that meet the 5 assumptions of the Hardy-Weinberg Principle said to be in?
Hardy-Weinberg Equilibrium
How are alleles and genotypes affected if populations are in Hardy-Weinberg equilibrium?
no change
What evolutionary agents are operating in a population if it is not in Hardy-Weinberg Equilibrium?
- natural selection
- non-random mating
- gene flow
- mutations
- small population size
Are mutations a strong evolutionary driver?
no, but they are the ultimate source of variation; individual mutations occur so rarely that mutation alone usually doesn’t change allele frequency much
Does gene flow occur because of seasonal migration? Why or why not?
no because the entire population moves and seasonal migration occurs outside of the breeding season
What is non-random mating?
mating with specific genotypes
What are the two types of non-random mating based on phenotype?
assortative and diassortative
What is assortative mating?
mating between phenotypically similar individuals
Does assortative mating increase homozygous individuals or heterozygous?
homozygous
What are two types of assortative mating?
inbreeding and self-fertilization
What is disassortative mating?
mating between phenotypically different individuals
Does disassortative mating increase homozygous individuals or heterozygous?
heterozygous
What is the strongest evolutionary driver?
natural selection
What is naturals selection?
environmental conditions determine which individuals in a population produce the most offspring
What 3 conditions must be met for natural selection to occur?
- variation must exist among individuals
- variation must result in differential survival of offspring
- variation must be genetically inherited
Is natural selection evolution?
no, it is a process by which change (evolution) MAY occur through time
Does natural selection always have an evolutionary result?
no
What is artificial selection?
a breeder/humans selects for desired characteristics
Does the environment affect artificial selection?
no
Does artificial selection affect entire species or just populations?
within own population, not necessarily entire species
What is the problem with small populations?
genetic drift
What is genetic drift?
the effect of chance on a population’s gene pool; frequencies of particular alleles may change by chance alone
Is genetic drift predictable?
no it is random
What are the two types of genetic drift?
founder effect and bottleneck effect
What is the founder effect?
- few individuals form a new population (small allelic pool)
- it is random which genotypes and phenotypes makes up the founding population
- isolated from where the population came from
What is the bottleneck effect?
- drastic reduction in population, and gene pool size
- by random chance there can be less variation
What are the causes of the bottleneck effect?
catastrophe, disease, over hunting
What value is most fit given?
1
What is fitness?
a phenotype with greater fitness usually increases in frequency
What does it mean if an individual is fit?
they survive longer and reproduce more
What is fitness a combination of?
survival, mating success, and number of offspring per mating that survive
What is survival?
how long does an organism live
What is mating success?
how often it mates
What are the three types of selection acting on traits affected by multiple genes?
directional, stabilizing, and disruptive (diversifying)
What is directional selection?
acts to eliminate one extreme from an array of phenotypes
What is stabilizing selection?
acts to eliminate both extremes; eliminates smaller and large ones and curve gets smaller
What is disruptive (diversifying) selection?
selection acts to eliminate intermediate types; selects for the extremes
What is oscillating selection?
one phenotype is favored at one time and another phenotype is favored at another
How does natural selection affect variation?
it can decrease it but it can also maintain it
What is frequency dependent selection?
favors phenotypes that are either common (positive f.d. selection) or rare (negative f.d. selection)
Does positive f.d. selection increase or decrease genetic variation?
decrease
Does negative f.d. selection increase or decrease genetic variation?
increase
What is a type of sexual selection?
sexual dimorphism
What is sexual dimorphism?
high degree of differences in outward appearance of females and males
Why do females tend to have a better investment in producing offspring?
females produce the offspring and often are the ones who take care of them, they have to make sure the offspring get enough nutrients
How do females evaluate males?
evaluate male secondary sexual characteristics to choose which potential mate has “better” genes
What is the handicap principle?
only the fittest individuals can afford costly traits (peacocks with larger tails attract females better but it is harder for them to survive with it, so the ones that do are fit)
What is the good genes hypothesis?
argues that individuals develop impressive ornaments to show off their efficient metabolism or ability to fight disease
Can more than one evolutionary agent be present in a population?
yes
What are the results of multiple evolutionary agents interacting in a population?
we can get speciation, but it is not a guarantee. The sum of the interactions determine whether evolution will occur
Does evolution have a purpose?
no, it doesn’t change populations into a preconceived ideal
What is evolution the sum of?
various forces and how they influence the population’s genetic and phenotypic variance
What is the only thing that is adaptive and results in a more fit population?
natural selection
What can actually decrease a population’s fitness?
gene flow and genetic drift
