Question 1

Genetic variation can originate both from the production of new alleles and from the arrangement of existing alleles.

Accepted Answer

Genetic variation can originate from the production of new alleles through genetic mutations, as well as from the arrangement of existing alleles through processes such as recombination and independent assortment during meiosis.

Question 2

What is the stable presence of more than one allele for a particular gene in a population called?

Accepted Answer

Balanced polymorphism refers to the situation where two or more alleles persist in a population because they each confer some selective advantage that allows them to be maintained in a stable frequency. This concept is key in understanding how genetic diversity is preserved within populations.

Question 3

What does natural selection result in?

Accepted Answer

Natural selection results in adaptation, where organisms become better suited to their environment over generations.

Question 4

What is the contribution that an individual makes to the gene pool of the next generation in relation to the contributions of other individuals called?

Accepted Answer

Relative fitness refers to the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals. It is a measure of an organism's reproductive success and is used in the context of natural selection.

Question 5

How could parasitism by wasps and feeding by birds result in a higher percentage of galls (made by gall-making flies) of medium size rather than small or large galls (or an even percentage of all sizes of galls)?

Accepted Answer

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Question 6

Which evolution-related events are in the correct cause-and-effect sequence?

Accepted Answer

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Question 7

Intermediate forms are often absent in characters showing qualitative variation.

Accepted Answer

Intermediate forms are often absent in characters showing qualitative variation because such traits are typically controlled by a single gene, leading to distinct, non-intermediate phenotypes.

Question 8

Which process below is NOT an agent of microevolutionary change?

Accepted Answer

Random mating does not cause microevolutionary change; instead, it maintains genetic diversity without changing the population's allele frequencies. Mutation, genetic drift, and natural selection directly contribute to changes in allele frequencies within a population, driving microevolution.

Question 9

How does gene flow introduce novel genetic variants into populations?

Accepted Answer

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Question 10

What is balanced polymorphism in a population likely the result of?

Accepted Answer

Balanced polymorphism is a situation in a population where two or more distinct traits in a population are maintained through natural selection. Disruptive selection, which favors individuals at both extremes of a trait over those with intermediate traits, is a mechanism that can lead to balanced polymorphism by supporting the survival and reproduction of individuals with distinct or extreme phenotypes, rather than those with average phenotypes.

Question 11

People with the disease known as sickle cell anemia are often better able to survive malaria. What is the cause of this?

Accepted Answer

Heterozygote advantage explains why individuals who are carriers of the sickle cell trait (having one normal allele and one sickle cell allele) have a survival advantage in malaria-endemic areas. They are less likely to suffer from severe effects of malaria compared to individuals with two normal alleles, while also avoiding the severe symptoms of sickle cell anemia that affect individuals with two sickle cell alleles.

Question 12

The distribution of the genetic disorder called sickle cell anemia is correlated with the distribution of malaria in tropical countries. What is this an example of?

Accepted Answer

This is an example of heterozygote advantage, where individuals who are heterozygous for the sickle cell trait have a survival advantage in areas where malaria is prevalent. They are less likely to suffer from severe effects of malaria compared to individuals without the trait, while also not suffering from the full effects of sickle cell anemia that homozygous individuals do.

Question 13

Under what circumstance might measuring the frequency of homozygous recessive genotypes lead to erroneous predictions of allele frequencies in a population?

Accepted Answer

Heterozygote advantage can maintain higher frequencies of heterozygotes than expected under Hardy-Weinberg equilibrium, leading to inaccurate predictions of allele frequencies if only homozygous recessive genotypes are measured.

Question 14

What is the founder effect a type of?

Accepted Answer

The founder effect is a type of genetic drift, which occurs when a new population is established by a very small number of individuals from a larger population. This can lead to significant changes in the gene pool of the new population, not because of natural selection but due to the random sampling of genes.

Question 15

Phenotypic variation CANNOT be passed on from one generation to the next.

Accepted Answer

Phenotypic variation can be passed on from one generation to the next if it has a genetic basis. Genetic variations that affect phenotype can be inherited, leading to inherited phenotypic traits.

Question 16

If you wanted to calculate the frequencies of the two different alleles for a particular gene in a population, what data would you have to gather and how would you use it?

Accepted Answer

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Question 17

What is any product of natural selection that increases the relative fitness of an organism in its environment called?

Accepted Answer

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Question 18

What is the decline in the occurrence of sickle cell anemia in the American population most likely the result of?

Accepted Answer

The decline in sickle cell anemia in the American population is most likely due to a decline in the occurrence of malaria in the United States. Sickle cell trait provides a survival advantage in regions where malaria is prevalent, leading to higher frequencies of the trait in those populations. As malaria became less common in the U.S., the selective pressure for sickle cell trait decreased, leading to a decline in its occurrence.

Question 19

What is inbreeding primarily due to?

Accepted Answer

Inbreeding is primarily due to non-random mating, where individuals mate with relatives or similar genotypes more frequently than would occur by chance, leading to an increase in homozygosity and potential expression of recessive traits.

Question 20

Distinguish between quantitative and qualitative variation.

Accepted Answer

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Quiz 17: Microevolution: Changes Within Populations