lecture 19- evolution of populations Flashcards
what is the smallest unit that can evolve
populations
what is the variability in populations due to
the environment and genetics
what is genetics the basis of
evolution
what is microevolution
change in the genetic makeup of a population from generation to generation
can lead to macroevolution
what is the gene pool
all the alleles for all the loci present in the population
what is genotype frequency
the proportion of a particular genotype in the population
how do you calculate the genotype frequency
by dividing the genotype number by the number of individual (490 AA out of 1000 individuals = 0.49)
what is allele frequency
the proportion of a specific allele in a population
how do you calculate allele frequency
count alleles separately and divide by 2x individuals (600 Aa = 600 A and 600 a divided by 2x 1000 individuals (2 alleles each) = 0.3 each) technically should add up to 1
how do you see the evolution of a population
you compare the allele frequencies of the first generation with the second generation
how do allele frequencies change
from environmental changes/outside factors
what happens when the population is in genetic equilibrium
the allele and genotype frequencies are not changing from generation to the next
what does HW principle/equilibrium stand for
Hardy-Weinberg
what are the characteristics of HW equilibrium
in large population where mating is random and likely the allele frequency will not change
what are the formulas for allele and genotype frquencies
allele: p + q = 1
genotype: p^2 + 2pq +q^2 = 1
where
p: dominant allele freq.
q: recessive allele freq.
p^2: homozygous dominant genotype freq.
2pq: heterozygous genotype frq.
q^2: homozygous recessive freq.
HW equilibrium equations meaning
any population that conforms to p^2 + 2pq + q^2 = 1 is at genetic equilibrium
wont tell us anything about evolving populations
what are the conditions for genetic equilibrium
random mating
no mutation
no natural selection
extremely large pop. size
no migration
factors that cause microevolution
mutations
sexual recombination
natural selection
genetic drift
gene flow
mutations effects and characteristics
only way of getting new genes and alleles
most occur in somatic cells
can only be transmitted if it occurs in gametes
low rate in animals and plants
little effect on population
sexual recombination effects
genetic variability
little effect from generation to generation
mostly just reshuffling
natural selection effects and characteristics
certain alleles are passed to the next gen. in greater proportions
major factor in changing allele frequencies
wha are the three types of genetic drift
bottleneck
founder effect
what is genetic drift
random evolutionary changes in a population
how allele frequencies can change unpredictably from one gen. to the next
alleles can be eliminated by chance
major factor affecting allele frequencies
effects of genetic drift
decrease in genetic variation in a population (smaller size)
increase in genetic differences between different populations
bottleneck effect
large population reduced to nothing because of a disaster
genetic drift continues to affect the gene pool until pop. becomes large enough to eliminate the effect of chance fluctuations
founder effect
few individuals becoming isolated from a larger population
bring only a small fraction of genetic variability with them
allele frequency is different than the parent population’s
what is gene flow
the gain or loss of alleles from the movement of fertile individuals
one loses alleles the other gains
will reduce differences between populations over time
counters gene flow and natural selection
major factor altering allele frequencies
what makes natural selection different than other factors than cause microevolution
only one that can lead to an adaptation to the environment
increases the frequencies of certain genotypes (survival of the fittest)
only adaptive and non-random mechanism
types of natural selection
directional selection
disruptive selection
stabilizing selection
what is directional selection
favors individuals at one end of the phenotypic range
what is disruptive selection
favors individuals at both extremes of the phenotypic range
what is stabilizing selection
favors intermediate individuals (against extremes phenotypes)
what creates the most genetic variation in a population
sexual reproduction
(crossing over, independent assortment, random fertilization)
original differences originated from mutations
is sexual reproduction a handicap and why
yes because its much slower and and results in less reproductive offsprings
what is sexual selection
natural selection for mating success
can result in sexual dimorphism
what is sexual dimorphism
differences between sexes in secondary sexual characteristics (colorful males)
what is intrasexual selection
direct competition among individuals of one sex for mates of the opposite sex (males fighting with other males)
what is intersexual selection
when one sex (usually females) are choosy in selecting their mates in the other sex (birds singing so female choose him)
