Question 1

In cases where selection consistently favors a higher (or lower)value of a trait or phenotype,the result over time is a change in the average value of a trait in the population.This mode of selection is known as ________.
A) directional selection
B) stabilizing selection
C) disruptive selection
D) selection gradient

Accepted Answer

Directional selection occurs when natural selection consistently favors individuals with higher or lower values of a trait, resulting in a shift in the average value of the trait in the population over time. Stabilizing and disruptive selection, on the other hand, tend to maintain the average value of a trait in the population. Selection gradient refers to the rate of change in the average trait value in relation to the strength of selection.

Question 2

When Bradshaw and colleagues investigated the quantitative trait loci (QTL)of two species of Mimulus (Mimulus cardinalis and Mimulus lewisii),they used marker loci as a way to map the QTLs.Their results are shown in the accompanying figure.According to these results,________. 
A) the differences in genotype for the majority of these QTLs explained small amounts of the variations in flower phenotypes for both species
B) some of the QTLs did have pronounced effects on the flowers' phenotypes
C) at least one QTL explained 90% of the phenotypic variance for each species
D) All of the above.

Accepted Answer

D

Question 3

The fraction known as the broad-sense heritability (where VG = genetic variation,VP = phenotypic variation,and VE = environmental variation)is expressed by ________.
A) VG/VP
B) VG/VG + VE
C) VG/VP + VE
D) VG/VE
E) A and B are both accurate.

Accepted Answer

Broad-sense heritability is defined as the proportion of the phenotypic variation in a population that is attributable to genetic variation among individuals. This can be expressed as H^2 = VG/VP, where VG is the genetic variation and VP is the total phenotypic variation (VP = VG + VE, with VE being the environmental variation). Both A and B correctly express this relationship, with B being a rearrangement of the formula to explicitly show the components of VP.

Question 4

Determining the slope of the best-fit line for a data set of midparent versus midoffspring values by utilizing least-squares linear regression generates an estimate of heritability known as the ________.
A) phenotypic variation
B) environmental variation
C) broad-sense heritability
D) narrow-sense heritability

Accepted Answer

Narrow-sense heritability is estimated by determining the slope of the best-fit line for a data set of midparent versus midoffspring values using least-squares linear regression. This method specifically estimates the proportion of phenotypic variation that is due to additive genetic factors, which is what narrow-sense heritability represents.

Question 5

The abbreviation QTL stands for ________,[three words] which are those genes that influence nonqualitative traits.

Accepted Answer

The answer of The abbreviation QTL stands for ________,[three words]...

Question 6

The authors of your textbook described two ways in which the strength of selection can be measured.What are these two ways?

Accepted Answer

The answer of The authors of your textbook described two...

Question 7

Heritability measures ________.
A) the difference between the environmental and genetic influences on a heritable trait of an individual
B) the degree of influence that the sum of the environmental and genetic factors have on a trait
C) the portion of the total variation in a trait that is due to variation in genes
D) the distribution of the phenotypes of the individuals in a normally distributed population

Accepted Answer

Heritability measures the proportion of variation in a trait that is due to variation in genes. It does not measure the specific difference between environmental and genetic influences, or the distribution of phenotypes in a population. Heritability does take into account both environmental and genetic factors, but it specifically measures the contribution of genetic factors to the variation in a trait.

Question 8

Continuously variable traits typically have a(n)________,[two words] otherwise known as a "bell-curve."

Accepted Answer

The answer of Continuously variable traits typically have a(n)________,[two words]...

Question 9

Traits that are conditioned by one locus are most appropriately termed ________.
A) qualitative traits
B) quantitative traits
C) continuously variable traits
D) environmentally conditioned traits

Accepted Answer

Qualitative traits are described as traits conditioned by a single gene or locus, with their expression resulting in discrete, phenotypic characteristics.

Question 10

The total variation in a trait is known as the ________.
A) phenotypic variation
B) genetic variation
C) environmental variation
D) broad-sense heritability
E) narrow-sense heritability

Accepted Answer

Phenotypic variation refers to the total variation in a trait, including both genetic and environmental influences. It is the sum of genetic variation (differences in DNA sequence) and environmental variation (differences in the environment that can affect gene expression and phenotype). Broad-sense heritability and narrow-sense heritability are measures of how much of the total variation in a trait can be attributed to genetic differences, and genetic variation refers to only the differences in DNA sequence.

Question 11

Multiple trait analysis (beak width and beak depth)on the medium ground finch,in response to the drought of 1976-77,has generated the three-dimensional graph,shown in the accompanying figure.If the blue triangles represent fitness levels for the quantified parameters,then the birds showing the greatest fitness should have ________. 
A) deep, wide beaks
B) deep, narrow beaks
C) shallow, wide beaks
D) shallow, narrow beaks

Accepted Answer

The answer of Multiple trait analysis (beak width and beak...

Question 12

________ refers to the fraction of the total variation in a trait that is due to variation in genes.

Accepted Answer

The answer of ________ refers to the fraction of the...

Question 13

Determining the best-fit line for a data set by utilizing the least-squares linear regression,the slope of the resulting line represents a useful estimate known as the ________,[two words] for which we use the symbol h².

Accepted Answer

The answer of Determining the best-fit line for a data...

Question 14

When Clausen and colleagues grew genetically identical individuals of the yarrow plant at different elevations,the results are shown in the accompanying figure.This observation verifies that ________. 
A) yarrow plants mutate quickly when grown in different environments
B) the genotypes of yarrow plants has nothing to do with how tall these plants grow
C) yarrow plants grow taller at lower elevations and shorter at higher elevations regardless of their genotype
D) the genotypes of yarrow plants interacts with environmental influences to produce the phenotype

Accepted Answer

The experiment grew genetically identical individuals of the yarrow plant at different elevations, and the results showed that the plants' height varied based on their genotype and environmental influences. This verifies that the genotypes of yarrow plants interact with environmental influences to produce the phenotype, making choice D the correct answer. Choice A is incorrect because the experiment does not provide any evidence that yarrow plants mutate quickly when grown in different environments. Choice B is incorrect because the experiment shows that genotype does play a role in how tall the plants grow. Choice C is also incorrect because the experiment reveals that the height of the plants varied based on their genotype and environmental influences.

Question 15

The experimental work of Edward East in 1916,shown in the accompanying figure,confirmed that ________. 
A) qualitative traits are essentially impossible to characterize because of their complex nature
B) quantitative traits are essentially impossible to characterize because of their complex nature
C) quantitative traits are established by the combined influence of Mendelian alleles at multiple loci
D) quantitative traits return to qualitative attributes when allowed to outcross in the wild

Accepted Answer

Edward East's work confirmed that quantitative traits are influenced by multiple genes, each contributing a small effect. This means that the expression of the trait depends on the combination of alleles at multiple loci, rather than a single gene. Therefore, quantitative traits cannot be explained by simple Mendelian genetics and require a more complex understanding of genotype-phenotype relationships.

Question 16

Variation among individuals that is due to variation in factors other than environmental influences is called ________.
A) phenotypic variation
B) genetic variation
C) broad-sense heritability
D) narrow-sense heritability

Accepted Answer

Genetic variation refers to the variation in traits that is due to genetic differences among individuals. This variation is heritable and can be passed down from parents to offspring. Phenotypic variation refers to the variation that is observable in traits and can be due to both genetic and environmental influences. Broad-sense heritability refers to the proportion of phenotypic variation that can be attributed to genetic variation, whereas narrow-sense heritability refers to the proportion of phenotypic variation that can be attributed to additive genetic variation.

Question 17

Traits that are conditioned by multiple loci and form continuously variable phenotypes that are conditioned by both the genotypes and environmental influences are most appropriately termed ________.
A) qualitative traits
B) quantitative traits
C) discrete categorical traits
D) Mendelian traits

Accepted Answer

Traits that are conditioned by multiple loci and form continuously variable phenotypes are referred to as quantitative traits. These traits are influenced by both genetic and environmental factors, and their expression does not follow simple Mendelian inheritance patterns. Quantitative traits exhibit continuous variation, and their inheritance is complex, involving many genes with relatively small effects.

Question 18

Data on survival of juvenile black-bellied seedcrackers as a function of beak size is shown in the accompanying figure.Given the relative survival rates of juvenile birds in terms of both the lower mandible width and length,this is a clear example of ________. 
A) directional selection
B) stabilizing selection
C) disruptive selection
D) selection gradient

Accepted Answer

The data shows that birds with either very small or very large beak sizes have lower survival rates compared to birds with intermediate beak sizes. This suggests that disruptive selection is at play, as extreme phenotypes are being selected against in favor of the intermediate phenotype.

Question 19

To learn the location of and determine the role that QTLs have on phenotypes,researchers look for associations between a marker locus genotype and phenotype.Examples of research focusing on such methods have been conducted on ________.
A) human personality traits
B) human diseases such as Crohn's disease
C) the speed of thoroughbred race horses
D) All of the above.

Accepted Answer

All of the given options represent examples of research where associations between marker loci genotypes and phenotypes are studied to determine the role QTLs have on them. For instance, in humans, research has been conducted on personality traits and diseases like Crohn's disease. Similarly, in horses, the speed of thoroughbred racehorses has been studied to understand the genetics behind the trait.

Question 20

Variation among individuals that is due to factors other than genetic factors is called ________.
A) phenotypic variation
B) environmental variation
C) broad-sense heritability
D) narrow-sense heritability

Accepted Answer

Environmental variation refers to differences among individuals that are caused by factors other than genetics, such as exposure to different environmental conditions or experiences. Phenotypic variation refers to any difference in observable traits among individuals, which can be caused by both genetic and environmental factors. Broad-sense heritability refers to the proportion of phenotypic variation that can be attributed to genetic factors, while narrow-sense heritability specifically refers to the fraction of phenotypic variation that is due to additive genetic effects.

Quiz 9: Evolution at Multiple Loci: Quantitative Genetics

In cases where selection consistently favors a higher (or lower) value of a trait or phenotype,the result over time is a change in the average value of a trait in the population.This mode of selection is known as ________.

When Bradshaw and colleagues investigated the quantitative trait loci (QTL) of two species of Mimulus (Mimulus cardinalis and Mimulus lewisii) ,they used marker loci as a way to map the QTLs.Their results are shown in the accompanying figure.According to these results,________.

The fraction known as the broad-sense heritability (where VG = genetic variation,VP = phenotypic variation,and VE = environmental variation) is expressed by ________.

Determining the slope of the best-fit line for a data set of midparent versus midoffspring values by utilizing least-squares linear regression generates an estimate of heritability known as the ________.

The abbreviation QTL stands for ________,[three words] which are those genes that influence nonqualitative traits.

The authors of your textbook described two ways in which the strength of selection can be measured.What are these two ways?

Heritability measures ________.

Continuously variable traits typically have a(n)________,[two words] otherwise known as a "bell-curve."

Traits that are conditioned by one locus are most appropriately termed ________.

The total variation in a trait is known as the ________.

________ refers to the fraction of the total variation in a trait that is due to variation in genes.

Determining the best-fit line for a data set by utilizing the least-squares linear regression,the slope of the resulting line represents a useful estimate known as the ________,[two words] for which we use the symbol h².

When Clausen and colleagues grew genetically identical individuals of the yarrow plant at different elevations,the results are shown in the accompanying figure.This observation verifies that ________.

The experimental work of Edward East in 1916,shown in the accompanying figure,confirmed that ________.

Variation among individuals that is due to variation in factors other than environmental influences is called ________.

Traits that are conditioned by multiple loci and form continuously variable phenotypes that are conditioned by both the genotypes and environmental influences are most appropriately termed ________.

Data on survival of juvenile black-bellied seedcrackers as a function of beak size is shown in the accompanying figure.Given the relative survival rates of juvenile birds in terms of both the lower mandible width and length,this is a clear example of ________.

To learn the location of and determine the role that QTLs have on phenotypes,researchers look for associations between a marker locus genotype and phenotype.Examples of research focusing on such methods have been conducted on ________.

Variation among individuals that is due to factors other than genetic factors is called ________.