Question 1

What is the difference between microevolution and macroevolution?

Accepted Answer

Microevolution refers to changes in gene frequency within a population over a short amount of time, whereas macroevolution involves the formation of new species and the evolution of major groups over longer periods of time. The distinction between micro and macroevolution is based on a time-scale difference rather than the size of organisms, populations or the degree of detectability.

Question 2

Imagine a population of monkeys in South America whose habitat has been reduced to the point where only 25 monkeys survive.This is an example of:

Accepted Answer

Population bottleneck occurs when a large population is drastically reduced in numbers, which can lead to a loss of genetic diversity and an increased likelihood of genetic disorders due to the limited number of individuals mating and passing on their genes. The scenario described in the question fits the definition of population bottleneck as the original population has been greatly reduced in numbers, resulting in a higher risk of genetic issues in the surviving monkeys. The other choices do not fully apply as the reduced population is not necessarily due to a founder event, genetic drift, or natural selection.

Question 3

The mate-attracting elaborate plumage of the male peacock is a result of:

Accepted Answer

The elaborate plumage of peacock is a result of sexual selection, as it is developed through competition for mating opportunities among males, rather than adaptation to the environment or random genetic drift. Gene flow refers to the exchange of genetic material between populations, which is not relevant to the development of the peacock's plumage.

Question 4

Shrews have been documented to travel across frozen lakes and establish populations on previously uninhabited islands; thus,the shrews have a limited gene pool.If this limited gene pool has allele frequencies that are very different from the allele frequencies found in the original population,then this would be an example of:

Accepted Answer

The establishment of populations on previously uninhabited islands and the subsequent limited gene pool suggest the occurrence of a founder effect where a small group of individuals become isolated and establish a new population with a limited genetic diversity. If the allele frequencies in this new population are different from those in the original population, this would be an example of founder effect.

Question 5

A population is:

Accepted Answer

A population refers to all the members of a species that live in a defined geographic region at the same time. Option A describes a subpopulation or a distinct breeding group within a population. Option C refers to a community, which includes populations of different species. Option D describes a taxonomic grouping which is broader than a population.

Question 6

After several generations,35 percent of the island population is found to have AB+ blood.This is much higher than the percentage of AB+ people in the populations from which the original settlers came.The high percentage of AB+ blood is probably due to:

Accepted Answer

The founder effect occurs when a small group of individuals migrates and establishes a new population with limited genetic diversity, resulting in a higher frequency of certain genetic traits that may have been rare in the original population. In this case, the high percentage of AB+ blood is likely due to the small number of original settlers who had this blood type, and their descendants passed on this trait to future generations.

Question 7

The formation of new species over many generations is an example of:

Accepted Answer

The formation of new species is an example of macroevolution, which involves the large-scale changes in the characteristics of species over long periods of time. Microevolution refers to smaller-scale changes within a population, such as changes in allele frequencies, gene pools, and allelic variants.

Question 8

If within a large population no mutations occur,no migration occurs,all mating is random,and each individual has an equal chance of reproducing,which of the following will probably happen?

Accepted Answer

In a scenario where there are no mutations, no migration, random mating, and equal chances of reproducing for all individuals, there is no mechanism for evolution to occur. Therefore, the most probable outcome is that no evolution will occur, and the population will remain stable over time. Neither a bottleneck event nor a change in allele frequency leading to rapid evolution is expected to occur in this situation. Extinction would only occur if there were external factors, such as environmental changes or catastrophes, that affect the survival of the population.

Question 9

The gene pool for a particular gene would include:

Accepted Answer

The gene pool refers to all the alleles for a particular gene within the entire population, not just one individual. Therefore, the correct option is D, all the alleles for a particular gene in all the individuals in the population.

Question 10

At its most basic level,evolution is a:

Accepted Answer

Evolution is primarily concerned with changes in populations over time. One of the most fundamental factors driving evolution is the frequency of alleles (different versions of a gene) within a population. As selective pressures change and certain traits become more or less advantageous, the frequency of different alleles will shift, leading to evolutionary change.

Question 11

The genetic makeup of any organism is its ________,which determines the physical characteristics called its ________.

Accepted Answer

Genotype refers to the genetic makeup of an organism, while phenotype refers to the physical characteristics that result from the genotype. Therefore, the genetic makeup (genotype) determines the physical characteristics (phenotype) of an organism. Alleles refer to the different forms of a gene that can exist within a population, and the gene pool refers to the total collection of genes and alleles within a population. Option A and B incorrectly mix up the terminology of genotype and gene pool, while option C reverses the relationship between genotype and phenotype.

Question 12

Organisms that can interbreed with each other in nature but are genetically isolated from all other organisms are a:

Accepted Answer

A species is defined as a group of organisms that can interbreed with each other in nature and produce viable, fertile offspring, but are genetically isolated from all other organisms. This isolation can occur due to geographical, behavioral, or genetic factors.

Question 13

The only known population of a reptile species lives on an African mountain.The population is relatively large,but no close relatives of this species are known.Suppose you could stop all mutations within the population and all emigration out of this population.Which statement best describes the probable future of this population?

Accepted Answer

Even if mutations stop, natural selection will continue to act on the existing genetic variability in the population. This could lead to further adaptation to the environment and the evolution of new traits. However, over time, genetic diversity will decrease due to inbreeding, which could eventually lead to decreased fitness and extinction.

Question 14

Which of the following is ultimately responsible for introducing new alleles into a population?

Accepted Answer

Mutations are the ultimate source of new alleles in a population. Mutations are spontaneous changes or errors that occur during DNA replication, which can lead to the creation of a new allele that was not previously present in the population. This new allele can then spread through the population through various mechanisms such as genetic drift, gene flow, or natural selection.

Question 15

If every sexually reproducing organism has only two alleles for each gene,how can there be a range of traits seen for a physical characteristic?

Accepted Answer

While an individual organism may only have two alleles for a gene, there can be multiple variations of that gene (alleles) present in a population. For example, the gene that determines human blood type has three different alleles (A, B, and O), resulting in four different blood types (A, B, AB, and O). Therefore, the range of physical characteristics seen within a population can be attributed to the presence of multiple alleles for a given gene.

Question 16

The most immediate effect of sexual displays and contests in animals (such as bighorn sheep bashing their heads together)is:

Accepted Answer

Sexual displays and contests often involve attracting and competing for mating partners, leading to differential mating success. Individuals with better displays or greater fighting ability are more likely to mate and pass on their genes, resulting in natural selection for those traits. The other choices, mutations, disruptive selection, and stabilizing selection, are not directly related to sexual displays and contests.

Question 17

As world travel becomes easier and human populations intermix,the occurrence of what phenomenon will probably decrease?

Accepted Answer

Founder effect and genetic drift occur when a small population separates from a larger one and establishes a new colony with limited genetic diversity. As world travel becomes easier and populations intermix, it is less likely for small groups to establish isolated colonies with limited genetic diversity. Therefore, the occurrence of founder effect and genetic drift is expected to decrease.

Question 18

Genetic drift occurs when:

Accepted Answer

Genetic drift occurs when chance occurrences, such as a natural disaster or random mating, alter the gene frequencies within a population. It is not related to nonrandom reproduction, gene flow, or stabilization of a population.

Question 19

Refer to the scenario below, and then answer the following question(s).
Two European men and two Polynesian women settled on a previously uninhabited tropical island. All four of the settlers have brown eyes, a dominant trait, but one of the Europeans is heterozygous and carries the recessive gene for blue eyes.
-No new settlers arrive,and nobody leaves the island.After a few generations,the percentage of blue-eyed individuals increases from the original zero to 25 percent.This is probably due to which of the following factors?

Accepted Answer

Genetic drift is a mechanism of evolution that refers to random fluctuations in the frequencies of alleles (variations of a gene) within a small population. In the scenario described, the isolated population on the island is small, and the increase in the percentage of blue-eyed individuals over generations can be attributed to the random chance that the recessive blue eye allele, carried by the heterozygous European, was passed on more frequently than expected by chance alone. Mutation and gene flow are not likely explanations in this context, as no new genetic information was introduced (mutation) or exchanged with other populations (gene flow).

Question 20

Which of the following statements about evolution is true?

Accepted Answer

Evolution occurs at the population level, as changes in the frequency of alleles (versions of genes) over time can result in changes in the traits of the population. While individuals can experience changes in their phenotype (observable traits), this does not necessarily represent evolution unless it is accompanied by a change in the genetic makeup of the population. Mutations are a critical source of genetic variation, which is required for evolution to occur, so D is incorrect. A is incorrect because evolution involves changes in the frequency of alleles, not maintaining a constant frequency.

Quiz 17: The Means of Evolution: Microevolution