bio 102 ch. 23
How do lactase supplements help people who are lactose intolerant?
The supplements provide the enzyme that breaks down the lactose in dairy products.
if individuals tend to mate within a subset of the population, there is...
no random mating
Generation-to-generation change in the allele frequencies in a population is _____.
microevolution
which of the following evolutionary forces could create new genetic information in a population
mutation
which one of the following conditions would most likely cause allele frequencies to change by chance
small populations
how did the grants test their hypothesis that differences in birds' songs can keep different species of finches from breeding with one another
they played the songs of medium ground finches and cactus finches through a loudspeaker to see which species responded to each song
True or false? The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating.
true
The Grants witnessed strong selection during droughts in 1977 and 1985. Compare the two droughts. (2)
- Both droughts events provided strong natural selection on medium ground finch populations. - Both droughts resulted in changes to food sources that favored the survival of some medium ground finches over others.
what applies to gene flow (2)
- a result of the movement of fertile individuals or their gametes - can introduce new alleles into a populations gene pool
what applies to genetic drift (3)
- causes allele frequencies to fluctuate randomly - can result from the founder effect - can result from the bottleneck effect
what applies to natural selection (3)
- consistently causes a population to become better adapted to its environment - a result of differential success in reproduction - cannot cause a harmful allele to become more common
the enzyme lactase breaks the sugar lactose intolerant which components (2)
- galactose - glucose
which of the following are causes of evolutionary change (4)
- gene flow - natural selection - genetic drift - mutation
How did Dr. Allison test his hypothesis that sickle cell disease was connected to malaria? (2)
- he evaluated blood samples for malaria parasites and the presence of sickle cells. -he expanded his study area beyond Kenya to the rest of East Africa to see if malaria and sickle disease were connected.
How does Dr. Allison's work provide an example of natural selection in humans? (2)
- in areas without malaria, individuals with two sickle cell alleles reproduced at lower rates than those without sickle cell disease. - in areas with malaria, individuals with one sickle cell allele reproduced at higher rates than those with no sickle cell alleles.
The film defines species as populations whose members don't interbreed. What keeps different Galápagos finch species from mating? (3)
- males only court females that have a similar beak and similar size -geographic isolation and different environments led to changes in traits that affected mating -individuals recognize and only respond to songs of their own species
How could milk-drinking have provided strong favorable selection for lactase persistence? (3)
- milk may have been a critical food source during times of famine - milk was safer to drink than water and reduced exposure to pathogens - milk is protein and fat-rich and therefore could have been an important, high-quality food source
if a person has 2 normal copies of the hemoglobin allele, which statements are true (2)
- the person is susceptible to malaria - the person is homozygous at the hemoglobin locus
in a Hardy-Weinberg population with two alleles A1 and A2 that are in equilibrium, the frequency of the allele A2 is 0.3. What is the frequency of individuals that are homozygous for this allele
0.09
consider a population of wildflowers in which the frequency of the red allele CR is p=0.7. what is the frequency of the white allele (CW) in this population?
0.3
in a Hardy-Weinberg population with two alleles A1 and A2 that are in equilibrium, the frequency of allele A2 is 0.2. What is the frequency of individuals that are heterozygous for this allele?
0.32
what is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals
0.4
A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?
0.42
a scientist samples a population of butterflies and finds that 56% are heterozygous at a particular locus. If the population is in Hardy-Weinberg equilibrium, what should the frequency of the homozygous individuals in this population?
0.44
a large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (A2A2), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygous indistinguishable from the homozygous dominants. what is the estimated frequency of allele A1 group?
0.50
in peas, a gene controls flower color such that R1= purple and R2= white. The purple allele is dominant to the white allele. In an isolated peach patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population
0.80
One out of 10,000 babies born in North America is affected by cystic fibrosis, a recessive condition. Assuming that the North American human population is in Hardy-Weinberg equilibrium for this trait, what percentage of the population is heterozygous for this trait? (Remember the equation for a population in Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1.)
2%
suppose 68% of the individuals in a remote mountain village can taste PTC and must, therefore, have at least one copy of the dominant PTC taster allele. If this population confirms to Hardy-Weinberg equilibrium for this gene, what percent of the population must be heterozygous for this trait?
48%
mutation is...
A change in a gene or chromosome.
bottleneck effect is...
A change in allele frequency following a dramatic reduction in the size of a population
genetic drift is...
A change in the allele frequency of a population as a result of chance events rather than natural selection.
natural selection is...
A natural process resulting in the evolution of organisms best adapted to the environment.
You read about soapberry bugs and select the correct statement describing relative fitness in these individuals.
A soapberry bug with high relative fitness has a relatively high number of offspring that survive to reproductive age.
which of the following best describes what we can determine about the evolution of the eye
A variety of species exist that are likely to be similar to common ancestors whose eyes evolved to different degrees over time.
Why should we not view lactose intolerance as a disease in adult humans?
Adult humans did not consume dairy products until fairly recently in our evolutionary history.
which discovery supports the hypothesis that evolution of the lactase-persistence trait was driven by the use of milk in pastoralist cultures
Ancient pots used to hold milk are about the same age as the lactase-persistence mutations.
Different finch species have beaks of different shapes and sizes. What do these beak differences tell us?
Different finch beak shapes are evidence that finch species adapted to different environments over many generations.
True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population.
False
which of the following are basic components of the Hardy-Weinberg model
Frequencies of two alleles in a gene pool before and after many random matings
Why is the enzyme lactase necessary to digest dairy products?
Lactase breaks down lactose into smaller molecules that can be absorbed by the cells that line the small intestine.
most people are lactose intolerant as adults, but nearly everyone produces sufficient lactase as an infant. However, in some cases, genetic mutations can occur that make an infant lactose intolerant. From an evolutionary perspective - over thousands of years - why would lactose intolerance in infants be very rare in the population
Lactose intolerant infants could not digest breast milk and therefore usually died, never having the chance to pass the mutation on to their children.
genetic evidence supports which of the following explanations for the presence of 13 different finch species on the Galápagos islands
Many years ago, a small population of a single finch species migrated to the islands and evolved into the current 13 species.
Compare sickle cell disease and malaria.
Sickle cell disease and malaria are both potentially lethal diseases.
What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2 for a particular gene?
The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2, and A2A2, respectively.
what is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals
The frequency of the A1 allele is 0.3.
which of the following statements is not a part of the Hardy-Weinberg principle
The genotype frequencies in the offspring generation must add up to two.
predict what will happen to the frequency of the sickle cell allele in areas where malaria has been eradicated
The sickle cell allele will decrease in frequency.
which statement correctly describes the role of chance in evolution
The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA.
A giraffe and a mouse (both mammals) have the same number of vertebrae in their neck and spine. Which of the following accounts for this?
The vertebrae in their neck and spine are homologous because they share a common ancestor.
Sharks (which are fish) and dolphins (which are mammals) are both shaped like a torpedo. Which of the following accounts for this?
Their shape arose through convergent evolution, since that shape is beneficial for animals living in the ocean.
lactose intolerance in infants is more common in the population today than it was a hundred years ago. why?
Today there are alternatives to breast milk, such as lactose-free formula and soy milk, so lactose intolerant infants can survive.
An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population happens to have broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, which of the following processes most likely caused this change
a bottleneck effect
which of the following best describes the likely evolutionary steps that led to a complex eye like we see in humans
a flat sheet of light-sensitive cells; light-sensitive cells in a cup; a pinhole camera without a lens; a pinhole camera with a lens
how does the term "lactase persistent" relate to the term "lactose tolerant"
a lactose persistent person is lactose tolerant
the original source of all genetic variation is...
mutation
which of the following statements is accurate with regard to a population in Hardy-Weinberg equilibrium
allele frequencies should not change from one generation to the next
which of the following situations leads to microevolution
alleles move between populations that differ in allele frequencies
When should a lactase supplement be taken in order to be most effective, and why?
at the same time the dairy product is consumed, so that the lactase will be in contact with the lactose
which of the following comparisons illustrates differences in phenotypes caused by the environment
bodies of "body builders" versus "couch potatoes"
which of the following is the best definition of evolution on the smallest scale
change in allele frequencies in a population over time
a researcher has maintained a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, the viability of the flies decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, which of the following approaches would be the best way to reverse this trend of decreased viability?
cross the flies with flies from another lab
which of the following results is the most likely outcome of increased gene flow between two populations
decreased genetic difference between the two populations
Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers?
disruptive selection
Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today?
directional selection
what type of selection tends to increase genetic variation
disruptive selection
which of the following best describes the cause of a bottleneck effect
drastic decrease in the size of the population
which statement about beak size or finches on the island of Daphne Major during prolonged drought is accurate
each birds survival was strongly influenced by the depth and strength of its beak as the drought persisted
cystic fibrosis is a genetic disorder in humans where the person has two homozygous recessive alleles for the gene. if the disease is left untreated, it causes severe health problems in the individual. If 9 people in 10,000 newborn babies have the disease, what are the expected frequencies of the dominant (A1) and the recessive (A2) alleles according to the Hardy-Weinberg equation?
f(A1) = 0.9700, f(A2) = 0.0300
true or false? organisms can change their DNA in order to become better adapted to their environment
false
What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population?
founder effect
the Dunkers are a religious group that moved from germany to pennsylvania in the mid-1700s. They do not marry with members outside their own community. Today, the Dunkers are genetically unique and differ in allele frequencies at many loci from all other populations, including those in their original homeland. Which of the following mechanisms most likely explains the genetic uniqueness of this population?
founder effect and genetic drift
Studies of the Neanderathal DNA revealed that there are more similarities to non-African DNA than reference sequences from West Africans. Additionally, scientists found that Neanderathal DNA is as closely related to East Asians as to Europeans. These patterns indicate that interbreeding occurred before human migration further east. which evolutionary force most likely generated these results?
gene flow
If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?
gene variability = 0%; number of alleles = 1
allele frequencies in a gene pool may shift randomly and by chance. What is this random shift called?
genetic drift
one population of species has 25 individuals, all with genotype AA; a second population of this species has 40 individuals, all with genotype aa. Assume that these populations live far apart but in similar environmental conditions. Based on this information, the observed genetic variation most likely resulted from?
genetic drift
the effect of which Hardy-Weinberg condition is affected by population size
genetic drift
founder effect is...
genetic drift that occurs after a small number of individuals colonize a new area
which of the following statements about genetic variation is accurate
genetic variation must be present in a population before natural selection can act upon the population
i'm 1949, Dr. Tony Allison observed a high frequency of Kenyans carrying the sickle cell allele in costal areas and near Lake Victoria, but a lower frequency in the highlands. What did he hypothesize
he hypothesized that there was a connection between malaria and sickle cell disease
which of the following statements best explains the need for the "2" in the 2pq term in the Hardy-Weinberg equation
heterozygotes can come about in two ways
in which country would you most likely find a higher incidence of lactase persistence
in a Scandinavian country where people historically raised dairy cattle and made cheese
over time, humans have steadily increased their movement across the continents of the Earth. Which of the following results has most likely been derived from these movements?
increased gene flow
natural selection changes allele frequencies because some _____ survive and reproduce better than others
individuals
in some populations 1 in 500 people have sickle cell disease. What is the reason that a potentially deadly, inherited disease is found at such high frequencies
individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population
what did researchers discover about the genetic mutation causing lactose persistence
it is found in a regulatory region (a "switch") upstream dod the lactase gene
which of the following is true of microevolution
it is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations
gene flow is...
movement of alleles from one population to another
in 1986 a nuclear power accident in Chernobyl, USSR, led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in Chernobyl area ever since. which of the following events most likely occurred in the rodent populations following the accident?
mutation led to increased genetic variation
The higher the proportion of loci that are ʺfixedʺ in a population, the lower is that populationʹs...
nucleotide variability and average heterozygosity
how quickly could evolution take place, going from the simplest light-sensitive cells to a fully functioning eye
over the course of 400,000 generations
According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool.
random mating
which of the following evolutionary forces consistently results in adaptive changes in allele frequencies
selection
Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards?
stabilizing selection
Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies?
stabilizing selection
the fruit fly Drosophila malanogaster has an allele that confers resistance to DDT and similar insecticides. Laboratory strains of D. melanogaster have been established from fries collected in the wild in the 1930s and the 1960s. Lab strains established in the 1930s have no alleles for DDT resistance. In lab strains established in the 1960s, the frequency of the DDT resistance allele is 37%. Which statement is correct?
the evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread
what does the wide variety of different types of animal eyes represent
the intermediate forms that probably occurred in the common ancestors of today's animals
The evolutionary effects of genetic drift are greatest when _____.
the population size is small
No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is
the reshuffling of alleles in sexual reproduction
a large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (A2A2), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygous indistinguishable from the homozygous dominants. What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (A2A2) has not changed over time?
the two phenotypes are about equally adaptive under laboratory conditions
In a bell-shaped curve, the x-axis of the graph represents which of the following?
the value of a particular characteristic; characteristics of an organism can include such traits as size and color