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20 Nov 2023, 23:05
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Difficulty:
85%
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Question Stats:
39% (01:34) correct
61%
(00:44)
wrong
based on 18
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A recent study of the eggs of tree frogs in Panama has provided insights into the concept of phenotypic plasticity. A biologist that studied the eggs observed that they would normally hatch a week after they were laid. However, by touching the eggs, the biologist could induce them to hatch immediately. The biologist likened this touch to the vibrations from an attacking snake. The implication was that the egg, even at an early stage, was flexible. It could either wait its usual full term to hatch, or hatch immediately in response to an environmental stressor. This example demonstrates phenotypic plasticity, which is the flexibility an organism has in expressing its genes. The phenotype is the expression of the genotype, or genetic makeup, and “plasticity” means the ability to change or adapt. Put another way, genotype is the inherited instructions that an organism receives from its genes, while phenotype is its physical appearance and actions.
Early theories of genetics relied on a direct cause model: everything about an organism, including its phenotype, was determined by its genotype. Phenotypic plasticity, on the other hand, allows for the inclusion of environmental factors. For example, some types of plants can allocate more resources to their roots when growing in low-nutrient soil, or change the size and thickness of their leaves in response to the amount of sunlight they receive. Although genes certainly play a major role, individual organisms are not different simply because they have different genes. Rather, organisms can express phenotypic differences in response to variations in ecosystem, diet, temperature and climate.
The passage implies that the concept of phenotypic plasticity challenges which traditional perspective in genetics?
A. The belief that genetic expression in organisms is primarily influenced by environmental factors.
B. The idea that phenotype variations among organisms are largely due to genetic differences.
C. The claim that an organism’s outward traits cannot vary unless its DNA sequence is first altered by mutation, regardless of environment
D. The notion that environmental factors have no significant impact on the genetic makeup of organisms.
E. The view that genetic instructions are not inheritable and are determined solely by external conditions.
Early theories of genetics relied on a direct cause model: everything about an organism, including its phenotype, was determined by its genotype. Phenotypic plasticity, on the other hand, allows for the inclusion of environmental factors. For example, some types of plants can allocate more resources to their roots when growing in low-nutrient soil, or change the size and thickness of their leaves in response to the amount of sunlight they receive. Although genes certainly play a major role, individual organisms are not different simply because they have different genes. Rather, organisms can express phenotypic differences in response to variations in ecosystem, diet, temperature and climate.
The passage implies that the concept of phenotypic plasticity challenges which traditional perspective in genetics?
A. The belief that genetic expression in organisms is primarily influenced by environmental factors.
B. The idea that phenotype variations among organisms are largely due to genetic differences.
C. The claim that an organism’s outward traits cannot vary unless its DNA sequence is first altered by mutation, regardless of environment
D. The notion that environmental factors have no significant impact on the genetic makeup of organisms.
E. The view that genetic instructions are not inheritable and are determined solely by external conditions.
20 Nov 2023, 23:05
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Official Solution:
A recent study of the eggs of tree frogs in Panama has provided insights into the concept of phenotypic plasticity. A biologist that studied the eggs observed that they would normally hatch a week after they were laid. However, by touching the eggs, the biologist could induce them to hatch immediately. The biologist likened this touch to the vibrations from an attacking snake. The implication was that the egg, even at an early stage, was flexible. It could either wait its usual full term to hatch, or hatch immediately in response to an environmental stressor. This example demonstrates phenotypic plasticity, which is the flexibility an organism has in expressing its genes. The phenotype is the expression of the genotype, or genetic makeup, and “plasticity” means the ability to change or adapt. Put another way, genotype is the inherited instructions that an organism receives from its genes, while phenotype is its physical appearance and actions.
Early theories of genetics relied on a direct cause model: everything about an organism, including its phenotype, was determined by its genotype. Phenotypic plasticity, on the other hand, allows for the inclusion of environmental factors. For example, some types of plants can allocate more resources to their roots when growing in low-nutrient soil, or change the size and thickness of their leaves in response to the amount of sunlight they receive. Although genes certainly play a major role, individual organisms are not different simply because they have different genes. Rather, organisms can express phenotypic differences in response to variations in ecosystem, diet, temperature and climate.
The passage implies that the concept of phenotypic plasticity challenges which traditional perspective in genetics?
A. The belief that genetic expression in organisms is primarily influenced by environmental factors.
B. The idea that phenotype variations among organisms are largely due to genetic differences.
C. The claim that an organism’s outward traits cannot vary unless its DNA sequence is first altered by mutation, regardless of environment
D. The notion that environmental factors have no significant impact on the genetic makeup of organisms.
E. The view that genetic instructions are not inheritable and are determined solely by external conditions.
A) Incorrect. The traditional model minimized environmental influence, so it did not claim genetic expression is “primarily” shaped by the environment. This statement describes the modern, plasticity-oriented view, not the older view being challenged.
B) Correct Answer. Early in the passage the author describes a “direct cause model” in which “everything about an organism, including its phenotype, was determined by its genotype.” That view assumes the observable differences between organisms come mainly from genetic differences. Phenotypic plasticity overturns that idea by showing that a single genotype can produce different phenotypes when environmental conditions change, as with the tree-frog eggs or nutrient-stressed plants. Therefore the concept challenges the belief that phenotype variation is largely a matter of differing genes.
C) Incorrect (tempting but too narrow). Saying traits “cannot vary unless DNA is first altered by mutation” adds a condition the passage never attributes to early genetic theory. The direct-cause model allowed different genotypes (inherited or mutated) to yield different phenotypes but did not insist that mutation was the only route to change. Because the option injects a detail the text does not discuss, it overstates and misrepresents the traditional perspective.
D) Incorrect. The older model did not deny that the environment affects organisms; it denied that the environment influences phenotype expression. A claim that the environment has “no impact on genetic makeup” is a different point and is not addressed in the passage.
E) Incorrect. No one in the passage argues that genetic instructions are “not inheritable.” Even early theorists accepted inheritance; they simply overstated its role in determining outward traits.
Answer: B
A recent study of the eggs of tree frogs in Panama has provided insights into the concept of phenotypic plasticity. A biologist that studied the eggs observed that they would normally hatch a week after they were laid. However, by touching the eggs, the biologist could induce them to hatch immediately. The biologist likened this touch to the vibrations from an attacking snake. The implication was that the egg, even at an early stage, was flexible. It could either wait its usual full term to hatch, or hatch immediately in response to an environmental stressor. This example demonstrates phenotypic plasticity, which is the flexibility an organism has in expressing its genes. The phenotype is the expression of the genotype, or genetic makeup, and “plasticity” means the ability to change or adapt. Put another way, genotype is the inherited instructions that an organism receives from its genes, while phenotype is its physical appearance and actions.
Early theories of genetics relied on a direct cause model: everything about an organism, including its phenotype, was determined by its genotype. Phenotypic plasticity, on the other hand, allows for the inclusion of environmental factors. For example, some types of plants can allocate more resources to their roots when growing in low-nutrient soil, or change the size and thickness of their leaves in response to the amount of sunlight they receive. Although genes certainly play a major role, individual organisms are not different simply because they have different genes. Rather, organisms can express phenotypic differences in response to variations in ecosystem, diet, temperature and climate.
The passage implies that the concept of phenotypic plasticity challenges which traditional perspective in genetics?
A. The belief that genetic expression in organisms is primarily influenced by environmental factors.
B. The idea that phenotype variations among organisms are largely due to genetic differences.
C. The claim that an organism’s outward traits cannot vary unless its DNA sequence is first altered by mutation, regardless of environment
D. The notion that environmental factors have no significant impact on the genetic makeup of organisms.
E. The view that genetic instructions are not inheritable and are determined solely by external conditions.
A) Incorrect. The traditional model minimized environmental influence, so it did not claim genetic expression is “primarily” shaped by the environment. This statement describes the modern, plasticity-oriented view, not the older view being challenged.
B) Correct Answer. Early in the passage the author describes a “direct cause model” in which “everything about an organism, including its phenotype, was determined by its genotype.” That view assumes the observable differences between organisms come mainly from genetic differences. Phenotypic plasticity overturns that idea by showing that a single genotype can produce different phenotypes when environmental conditions change, as with the tree-frog eggs or nutrient-stressed plants. Therefore the concept challenges the belief that phenotype variation is largely a matter of differing genes.
C) Incorrect (tempting but too narrow). Saying traits “cannot vary unless DNA is first altered by mutation” adds a condition the passage never attributes to early genetic theory. The direct-cause model allowed different genotypes (inherited or mutated) to yield different phenotypes but did not insist that mutation was the only route to change. Because the option injects a detail the text does not discuss, it overstates and misrepresents the traditional perspective.
D) Incorrect. The older model did not deny that the environment affects organisms; it denied that the environment influences phenotype expression. A claim that the environment has “no impact on genetic makeup” is a different point and is not addressed in the passage.
E) Incorrect. No one in the passage argues that genetic instructions are “not inheritable.” Even early theorists accepted inheritance; they simply overstated its role in determining outward traits.
Answer: B
28 Dec 2023, 06:22
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Hi GMAT Club experts,
Can someone please explain why option C is incorrect?
"Early theories of genetics relied on a cause-and-effect model: everything about an organism, including its phenotype, was determined by its genotype. Phenotypic plasticity, on the other hand, allows for the inclusion of environmental factors"
As per the earlier theory, Genotype was the sole reason for phenotype. but now phenotypic plasticity allows for the INCLUSION of environmental factors.
Plus the author says that though genes play A MAJOR ROLE they are not the sole reason for phenotypic plasticity "Although genes certainly play a major role, individual organisms are not different simply because they have different genes."
C aptly encapsulates the above.
I was confused between B and C but I eliminated B because author stated that genes play a major role.
Please let me know where my understanding is incorrect?
Thanks,
