Determining whether a given population of animals constitutes a distinct species can be difficult because no single accepted definition of the term exists. One approach, called the biological species concept, bases the definition on reproductive compatibility. According to this view, a species is a group of animals that can mate with one another to produce fertile offspring but cannot mate successfully with members of a different group. Yet this idea can be too restrictive. First, mating between groups labeled as different species (hybridization), as often occurs in the canine family, is quite common in nature. Second, sometimes the differences between two populations might not prevent them from interbreeding, even though they are dissimilar in traits unrelated to reproduction; some biologists question whether such disparate groups should be considered a single species. A third problem with the biological species concept is that investigators cannot always determine whether two groups that live in different places are capable of interbreeding.

When the biological species concept is difficult to apply, some investigators use phenotype, an organism’s observable characteristics, instead. Two groups that have evolved separately are likely to display measurable differences in many of their traits, such as skull size or width of teeth. If the distribution of measurements from one group does not overlap with those of another, the two groups might reasonably be considered distinct species.

The passage is primarily concerned with

Determining whether a given population of animals constitutes a distinct species can be difficult because no single accepted definition of the term exists. One approach, called the biological species concept, bases the definition on reproductive compatibility. According to this view, a species is a group of animals that can mate with one another to produce fertile offspring but cannot mate successfully with members of a different group. Yet this idea can be too restrictive. First, mating between groups labeled as different species (hybridization), as often occurs in the canine family, is quite common in nature. Second, sometimes the differences between two populations might not prevent them from interbreeding, even though they are dissimilar in traits unrelated to reproduction; some biologists question whether such disparate groups should be considered a single species. A third problem with the biological species concept is that investigators cannot always determine whether two groups that live in different places are capable of interbreeding.

When the biological species concept is difficult to apply, some investigators use phenotype, an organism’s observable characteristics, instead. Two groups that have evolved separately are likely to display measurable differences in many of their traits, such as skull size or width of teeth. If the distribution of measurements from one group does not overlap with those of another, the two groups might reasonably be considered distinct species.

The author of the passage mentions “groups that live in different places” (in line 21) most probably in order to

Determining whether a given population of animals constitutes a distinct species can be difficult because no single accepted definition of the term exists. One approach, called the biological species concept, bases the definition on reproductive compatibility. According to this view, a species is a group of animals that can mate with one another to produce fertile offspring but cannot mate successfully with members of a different group. Yet this idea can be too restrictive. First, mating between groups labeled as different species (hybridization), as often occurs in the canine family, is quite common in nature. Second, sometimes the differences between two populations might not prevent them from interbreeding, even though they are dissimilar in traits unrelated to reproduction; some biologists question whether such disparate groups should be considered a single species. A third problem with the biological species concept is that investigators cannot always determine whether two groups that live in different places are capable of interbreeding.

When the biological species concept is difficult to apply, some investigators use phenotype, an organism’s observable characteristics, instead. Two groups that have evolved separately are likely to display measurable differences in many of their traits, such as skull size or width of teeth. If the distribution of measurements from one group does not overlap with those of another, the two groups might reasonably be considered distinct species.

With which of the following statements regarding the classification of individual species would the author most likely agree?

Determining whether a given population of animals constitutes a distinct species can be difficult because no single accepted definition of the term exists. One approach, called the biological species concept, bases the definition on reproductive compatibility. According to this view, a species is a group of animals that can mate with one another to produce fertile offspring but cannot mate successfully with members of a different group. Yet this idea can be too restrictive. First, mating between groups labeled as different species (hybridization), as often occurs in the canine family, is quite common in nature. Second, sometimes the differences between two populations might not prevent them from interbreeding, even though they are dissimilar in traits unrelated to reproduction; some biologists question whether such disparate groups should be considered a single species. A third problem with the biological species concept is that investigators cannot always determine whether two groups that live in different places are capable of interbreeding.

When the biological species concept is difficult to apply, some investigators use phenotype, an organism’s observable characteristics, instead. Two groups that have evolved separately are likely to display measurable differences in many of their traits, such as skull size or width of teeth. If the distribution of measurements from one group does not overlap with those of another, the two groups might reasonably be considered distinct species.

Which of the following best describes the function of lines 10-13 (highlight text)?

CResearchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behaviors are governed by more than one gene, and until recently geneticists had no method for identifying the multiple genes involved. In addition, even when a single gene is found to control a behavior, researchers in different fields do not necessarily agree that it is a “behavioral gene.” Neuroscientists, whose interest in genetic research is to understand the nervous system (which generates behavior), define the term broadly. But ethologists—specialists in animal behavior—are interested in evolution, so they define the term narrowly. They insist that mutations in a behavioral gene must alter a specific normal behavior and not merely make the organism ill, so that the genetically induced behavioral change will provide variation that natural selection can act upon, possibly leading to the evolution of a new species. For example, in the fruit fly, researchers have identified the gene Shaker, mutations in which cause flies to shake violently under anesthesia. Since shaking is not healthy, ethologists do not consider Shaker a behavioral gene. In contrast, ethologists do consider the gene period (per), which controls the fruit fly’s circadian (24-hour) rhythm, a behavioral gene because flies with mutated per genes are healthy; they simply have different rhythms.

The primary purpose of the passage is to

Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behaviors are governed by more than one gene, and until recently geneticists had no method for identifying the multiple genes involved. In addition, even when a single gene is found to control a behavior, researchers in different fields do not necessarily agree that it is a “behavioral gene.” Neuroscientists, whose interest in genetic research is to understand the nervous system (which generates behavior), define the term broadly. But ethologists—specialists in animal behavior—are interested in evolution, so they define the term narrowly. They insist that mutations in a behavioral gene must alter a specific normal behavior and not merely make the organism ill, so that the genetically induced behavioral change will provide variation that natural selection can act upon, possibly leading to the evolution of a new species. For example, in the fruit fly, researchers have identified the gene Shaker, mutations in which cause flies to shake violently under anesthesia. Since shaking is not healthy, ethologists do not consider Shaker a behavioral gene. In contrast, ethologists do consider the gene period (per), which controls the fruit fly’s circadian (24-hour) rhythm, a behavioral gene because flies with mutated per genes are healthy; they simply have different rhythms.

The passage suggests that neuroscientists would most likely consider Shaker to be which of the following?

Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behaviors are governed by more than one gene, and until recently geneticists had no method for identifying the multiple genes involved. In addition, even when a single gene is found to control a behavior, researchers in different fields do not necessarily agree that it is a “behavioral gene.” Neuroscientists, whose interest in genetic research is to understand the nervous system (which generates behavior), define the term broadly. But ethologists—specialists in animal behavior—are interested in evolution, so they define the term narrowly. They insist that mutations in a behavioral gene must alter a specific normal behavior and not merely make the organism ill, so that the genetically induced behavioral change will provide variation that natural selection can act upon, possibly leading to the evolution of a new species. For example, in the fruit fly, researchers have identified the gene Shaker, mutations in which cause flies to shake violently under anesthesia. Since shaking is not healthy, ethologists do not consider Shaker a behavioral gene. In contrast, ethologists do consider the gene period (per), which controls the fruit fly’s circadian (24-hour) rhythm, a behavioral gene because flies with mutated per genes are healthy; they simply have different rhythms.

It can be inferred from the passage that which of the following, if true, would be most likely to influence ethologists’ opinions about whether a particular gene in a species is a behavioral gene?

The poverty line, also known as the poverty threshold, is defined as the minimum level of income that is necessary for the people of a specific nation. The poverty line of a country is calculated by identifying the total amount of necessary expenses that an average adult requires over the course of one year, with the main such expense usually being house rent. Additionally, this calculation also typically includes the basic expenses of food and clothing. This measure of minimum income required is purely quantitative and does not estimate either the specific needs of people from different low-income groups or the different ways in which low-income groups experience poverty in different countries. The solely quantitative basis of calculating the minimum required income, therefore, may in fact lead to either the overestimation or the underestimation of the number of people who actually live under the poverty line in a given country. Another reason that renders the poverty line short of being a very reliable indicator of actual poverty levels is that certain nations, usually developed ones, with strong welfare systems fail to account for ‘in-kind’ transfers when calculating the poverty threshold. Such calculations do not regard the benefits received from antipoverty programs such as food stamps, housing assistance, etc. as income, thereby presenting a distorted picture of the level of poverty in the nation.

The primary purpose of the passage is to

The poverty line, also known as the poverty threshold, is defined as the minimum level of income that is necessary for the people of a specific nation. The poverty line of a country is calculated by identifying the total amount of necessary expenses that an average adult requires over the course of one year, with the main such expense usually being house rent. Additionally, this calculation also typically includes the basic expenses of food and clothing. This measure of minimum income required is purely quantitative and does not estimate either the specific needs of people from different low-income groups or the different ways in which low-income groups experience poverty in different countries. The solely quantitative basis of calculating the minimum required income, therefore, may in fact lead to either the overestimation or the underestimation of the number of people who actually live under the poverty line in a given country. Another reason that renders the poverty line short of being a very reliable indicator of actual poverty levels is that certain nations, usually developed ones, with strong welfare systems fail to account for ‘in-kind’ transfers when calculating the poverty threshold. Such calculations do not regard the benefits received from antipoverty programs such as food stamps, housing assistance, etc. as income, thereby presenting a distorted picture of the level of poverty in the nation.

Which of the following can be inferred from the last two sentences of the passage?

The poverty line, also known as the poverty threshold, is defined as the minimum level of income that is necessary for the people of a specific nation. The poverty line of a country is calculated by identifying the total amount of necessary expenses that an average adult requires over the course of one year, with the main such expense usually being house rent. Additionally, this calculation also typically includes the basic expenses of food and clothing. This measure of minimum income required is purely quantitative and does not estimate either the specific needs of people from different low-income groups or the different ways in which low-income groups experience poverty in different countries. The solely quantitative basis of calculating the minimum required income, therefore, may in fact lead to either the overestimation or the underestimation of the number of people who actually live under the poverty line in a given country. Another reason that renders the poverty line short of being a very reliable indicator of actual poverty levels is that certain nations, usually developed ones, with strong welfare systems fail to account for ‘in-kind’ transfers when calculating the poverty threshold. Such calculations do not regard the benefits received from antipoverty programs such as food stamps, housing assistance, etc. as income, thereby presenting a distorted picture of the level of poverty in the nation.

Which of the following statements about the poverty line would the author most likely agree with?

The poverty line, also known as the poverty threshold, is defined as the minimum level of income that is necessary for the people of a specific nation. The poverty line of a country is calculated by identifying the total amount of necessary expenses that an average adult requires over the course of one year, with the main such expense usually being house rent. Additionally, this calculation also typically includes the basic expenses of food and clothing. This measure of minimum income required is purely quantitative and does not estimate either the specific needs of people from different low-income groups or the different ways in which low-income groups experience poverty in different countries. The solely quantitative basis of calculating the minimum required income, therefore, may in fact lead to either the overestimation or the underestimation of the number of people who actually live under the poverty line in a given country. Another reason that renders the poverty line short of being a very reliable indicator of actual poverty levels is that certain nations, usually developed ones, with strong welfare systems fail to account for ‘in-kind’ transfers when calculating the poverty threshold. Such calculations do not regard the benefits received from antipoverty programs such as food stamps, housing assistance, etc. as income, thereby presenting a distorted picture of the level of poverty in the nation.

Which of the following is mentioned in the passage?