Natural Selection - TOEFL iBT® Reading Practice Questions with Answer Key

Achieving proficiency in the TOEFL Reading section demands adept analytical abilities tailored for academic English content. This segment evaluates your capacity to comprehend main concepts, discern crucial information, make logical deductions, and navigate text organization. The key? Regular practice!

Therefore, we present you with our practice tests that closely replicate the format and style of the real exam, fostering familiarity and assurance for test day. Ready to achieve your target score in the TOEFL Reading section? Let's take this practice test focused on "Natural Selection" to glean valuable insights into the structure and areas for enhancement!

Reading Instructions

• You have 15 minutes to read the following passage and answer all 10 questions related to it.  
• Most questions are worth 1 point, but the last question is worth more. The directions indicate how many points you will receive for that specific question. 
• The specific section/paragraphs have been provided again with the question for ease of understanding and quick solution.
• Some questions include a word or phrase that is highlighted in the question as well as in the paragraph for quick reference. 
  

Natural Selection 

Natural selection refers to the process where certain individuals with advantageous traits are more likely to survive and reproduce, leading to changes in the characteristics of a population over time, known as evolution. This concept was widely promoted by Charles Darwin, who distinguished it from artificial selection, which involves deliberate human intervention.

Variation is common among all populations of organisms, largely due to the occurrence of random mutations in individual organisms' genomes, which can then be passed on to their offspring. Throughout an organism's life, interactions between its genome and environment lead to variations in traits. This environment encompasses various biological factors within the organism, as well as external factors such as interactions with other organisms and the surrounding environment. As individuals with advantageous trait variants tend to have higher survival and reproduction rates, the population gradually evolves. Additional factors influencing reproductive success include sexual selection (now often considered part of natural selection) and fecundity selection.

Natural selection operates on the phenotype, the observable traits of an organism that interact with the environment. However, the genetic basis underlying advantageous phenotypes can become more prevalent in a population over time. This phenomenon can lead to populations specializing in specific ecological niches (microevolution) and may eventually lead to the emergence of new species (macroevolution), a process known as speciation. In essence, natural selection plays a crucial role in the evolutionary trajectory of populations.

Natural selection stands as a fundamental principle in modern biology. Initially proposed by Darwin and Alfred Russel Wallace in a joint presentation of papers in 1858, the concept was further expounded upon in Darwin's influential 1859 work, "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life." Darwin likened natural selection to artificial selection, the process by which desirable traits are deliberately chosen for breeding by humans. Notably, the concept of natural selection emerged before the development of a comprehensive theory of heredity; genetics, as we understand it today, had yet to be established during Darwin's era. It was not until the mid-20th century that the integration of traditional Darwinian evolution with advancements in classical genetics gave rise to the modern synthesis. Subsequent contributions from molecular genetics have further enriched our understanding of evolutionary processes, leading to the emergence of evolutionary developmental biology, which delves into evolution at the molecular level. While genotypes may undergo gradual changes through random genetic drift, natural selection remains the primary driving force behind adaptive evolution.

Moreover, the concept of natural selection has endured as the cornerstone of evolutionary theory despite advancements in genetics and molecular biology. It continues to provide a robust framework for understanding how organisms adapt to their environments over time. Natural selection operates on the variation present within populations, favoring traits that confer a reproductive advantage in a given ecological context. Through the accumulation of beneficial genetic variations, populations can undergo microevolutionary changes, leading to the specialization of organisms for specific ecological niches. Over longer periods, these incremental changes may culminate in macroevolutionary events such as speciation, where new species emerge from ancestral populations. Thus, natural selection remains central to our comprehension of the dynamic processes driving the diversity of life on Earth.

Directions: Once you have read the passage, answer the following questions.

Paragraph 1

Natural selection refers to the process where certain individuals with advantageous traits are more likely to survive and reproduce, leading to changes in the characteristics of a population over time, known as evolution. This concept was widely promoted by Charles Darwin, who distinguished it from artificial selection, which involves deliberate human intervention.

1. As per the paragraph 1, what defines natural selection?
   1. The deliberate survival and reproduction of individuals based on phenotype disparities
   2. The spontaneous alterations in an individual organism's genome
   3. The varied survival and reproduction of individuals owing to phenotype differences
   4. The inherited characteristics of a population across successive generations

1. Why does the author refer to Charles Darwin in the paragraph?
   1. To highlight the contrast between natural selection and artificial selection
   2. To elucidate the concept of natural selection
   3. To delve into the evolution of a population
   4. To provide insight into the theory of heredity

Paragraph 2

Variation is common among all populations of organisms, largely due to the occurrence of random mutations in individual organisms' genomes, which can then be passed on to their offspring. Throughout an organism's life, interactions between its genome and environment lead to variations in traits. This environment encompasses various biological factors within the organism, as well as external factors such as interactions with other organisms and the surrounding environment. As individuals with advantageous trait variants tend to have higher survival and reproduction rates, the population gradually evolves. Additional factors influencing reproductive success include sexual selection (now often considered part of natural selection) and fecundity selection.

1. According to Paragraph 2, what constitutes the genome's environment?
   1. The organism's traits
   2. The genetic foundation of any phenotype
   3. The non-living surroundings
   4. The molecular biology within the cell, interactions with other cells, individuals, populations, species, and the non-living environment

1. What is the author's primary intention in detailing the various factors influencing reproductive success in the given paragraph?
   1. To provide a comprehensive overview of genetic mutations in populations
   2. To highlight the complexities involved in natural selection processes
   3. To analyze the interplay between environmental factors and evolutionary adaptation
   4. To demonstrate the multifaceted nature of trait variation in organism populations

Paragraph 3

Natural selection operates on the phenotype, the observable traits of an organism that interact with the environment. However, the genetic basis underlying advantageous phenotypes can become more prevalent in a population over time. This phenomenon can lead to populations specializing in specific ecological niches (microevolution) and may eventually lead to the emergence of new species (macroevolution), a process known as speciation. In essence, natural selection plays a crucial role in the evolutionary trajectory of populations.

1. In the passage, the term "phenotype" is most similar in meaning to which of the following?
   1. The heritable traits of a population over generations
   2. The characteristics of the organism
   3. The environment of a genome
   4. The random mutations of the genome of an individual organism

1. In the context of the passage, the term "microevolution" is most analogous to which of the following?
   1. Population evolution
   2. Population adaptation
   3. Population specialization
   4. Population selection

Paragraph 5

Moreover, the concept of natural selection has endured as the cornerstone of evolutionary theory despite advancements in genetics and molecular biology. It continues to provide a robust framework for understanding how organisms adapt to their environments over time. Natural selection operates on the variation present within populations, favoring traits that confer a reproductive advantage in a given ecological context. Through the accumulation of beneficial genetic variations, populations can undergo microevolutionary changes, leading to the specialization of organisms for specific ecological niches. Over longer periods, these incremental changes may culminate in macroevolutionary events such as speciation, where new species emerge from ancestral populations. Thus, natural selection remains central to our comprehension of the dynamic processes driving the diversity of life on Earth.

1. Which term best describes the overarching framework provided by natural selection in the context of evolutionary theory?
   1. Genetic accumulation
   2. Ecological specialization
   3. Phenotypic adaptation
   4. Macroevolutionary mechanism

1. In the context of the passage, what is implied by the phrase "microevolutionary changes"?
   1. Gradual alterations in ecological niches
   2. Sudden shifts in reproductive strategies
   3. Incremental adjustments in genetic composition
   4. Rapid adaptations to environmental stressors

Paragraph 4

Natural selection stands as a fundamental principle in modern biology. (A) Initially proposed by Darwin and Alfred Russel Wallace in a joint presentation of papers in 1858, the concept was further expounded upon in Darwin's influential 1859 work, "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life." (B) Darwin likened natural selection to artificial selection, the process by which desirable traits are deliberately chosen for breeding by humans. (C) Notably, the concept of natural selection emerged before the development of a comprehensive theory of heredity; genetics, as we understand it today, had yet to be established during Darwin's era. (D) It was not until the mid-20th century that the integration of traditional Darwinian evolution with advancements in classical genetics gave rise to the modern synthesis. Subsequent contributions from molecular genetics have further enriched our understanding of evolutionary processes, leading to the emergence of evolutionary developmental biology, which delves into evolution at the molecular level. While genotypes may undergo gradual changes through random genetic drift, natural selection remains the primary driving force behind adaptive evolution.

1. Directions: Review the excerpt from the passage provided above. The letters (A), (B), (C), and (D) denote where the subsequent sentence could be incorporated.
   
   The book provided a thorough explanation of the concept of natural selection.
   
   Where would the sentence most appropriately belong?
   1. Choice A
   2. Choice B
   3. Choice C
   4. Choice D

1. Directions: You will find an introductory sentence for a summary of the passage provided below. Your task is to complete the summary by selecting the THREE answer choices that best represent the key ideas in the passage. Be mindful that some sentences may not align with the main ideas or may have minor ideas in the passage. This question carries a weight of 2 points.
   
   Natural selection, pivotal in evolution, denotes the varied survival and reproduction rates of individuals based on phenotype disparities, stemming from the interplay of their genetic makeup and surroundings.
   

   •

   •

   •

   Answer Choices

   1. Natural selection arises from the interplay between an organism's genome and its environment. 
   2. Charles Darwin popularized the term, distinguishing it from intentional artificial selection. 
   3. Favorable genetic traits leading to reproductive advantages can proliferate in populations, potentially driving evolution and speciation. 
   4. It's important to note that natural selection occurs across all organisms, including both plants and animals. 
   5. Unlike artificial selection, which is human-driven, natural selection is not deliberate. 
   6. Natural selection, not random genetic drift, primarily explains adaptive evolution.

Hold on!  Before checking your answers and matching them, explore what is a good TOEFL score!

Answer Key with Explanation for TOEFL Reading Passage - Natural Selection

1.  Answer: A

Explanation: This is a Factual Question and the right answer is A. In the provided passage, the definition of natural selection is described as the "differential survival and reproduction of individuals due to differences in phenotype." This definition implies that natural selection is not deliberate but rather a result of environmental pressures acting on phenotypic variations within a population. Therefore, option A is the correct choice as it accurately captures the essence of the definition provided in the passage.

Option C is incorrect because it does not fully capture the aspect of intentionality mentioned in the passage. Natural selection is not described as "varied survival and reproduction," but rather as a process of differential survival and reproduction based on specific phenotypic traits. Option B is incorrect because it does not align with the definition of natural selection as described in the passage. Natural selection does not directly involve spontaneous alterations in an organism's genome but rather acts on existing genetic variation within populations. Option D is incorrect because it focuses solely on inheritance and does not encompass the key aspect of differential survival and reproduction based on phenotype disparities, which is central to the concept of natural selection.

2. Answer: B

Explanation: This is a Rhetorical Purpose Question. The correct answer is B because the author mentions Charles Darwin to explain the concept of natural selection. Darwin's work, particularly his book "On the Origin of Species," elaborates on the theory of natural selection and its significance in evolutionary biology.

Option A is incorrect because while the contrast between natural and artificial selection is mentioned in the paragraph, it is not the primary purpose of mentioning Charles Darwin. Option C is incorrect because while natural selection is related to the evolution of populations, the specific mention of Charles Darwin is to explain the concept of natural selection itself, rather than the broader topic of population evolution. Option D is incorrect because while Darwin's work did contribute to the understanding of heredity to some extent, his primary contribution, especially in the context of this paragraph, is the theory of natural selection. 

3. Answer: D

Explanation: This is a Factual type question and the correct answer is D. In Paragraph 2, the environment of a genome is described as including various biological factors within the organism, as well as external factors such as interactions with other organisms and the surrounding environment. The passage specifically mentions "the molecular biology within the cell, other cells, other individuals, populations, species, as well as the abiotic environment," encompassing both living and non-living elements. Therefore, option D accurately reflects the comprehensive nature of the genome's environment as described in the passage.

Option A is incorrect because the genome's environment refers to the broader context in which genetic interactions occur, including both internal and external factors beyond individual traits. Option B is incorrect because it focuses solely on the genetic aspect and does not encompass the broader environmental factors mentioned in the passage. Option C is incorrect because it only captures one aspect of the genome's environment (the abiotic environment) and does not include the biological interactions within and among organisms as described in the passage.

4. Answer: B

Explanation: This is a Rhetorical purpose question. The correct answer is B) To highlight the complexities involved in natural selection processes. The author's primary intention in detailing the various factors influencing reproductive success is to highlight the complexities involved in natural selection processes. By discussing factors such as sexual selection and fecundity selection, the passage emphasizes that reproductive success is influenced by multiple factors beyond just survival. This serves to underscore the intricate nature of natural selection and its role in shaping population dynamics. Therefore, option B best reflects the author's intention to highlight the complexities of natural selection processes.

5. Answer: B 

Explanation: This is a Vocabulary question that pertains to the word "phenotype" highlighted in paragraph 5. The correct answer is B. In the context of the passage, "phenotype" refers to the observable characteristics or traits of an organism, such as its physical appearance or behavior. These traits are determined by the interaction between the organism's genetic makeup (genotype) and its environment.

6. Answer: A

Explanation: This is a Vocabulary question that pertains to the word "microevolution" highlighted in paragraph 5. The correct answer is choice A. In the passage, "microevolution" is described as the process by which populations undergo incremental changes over time, resulting in the specialization of organisms for specific ecological niches. This process involves the accumulation of beneficial genetic variations within populations, leading to changes in allele frequencies over generations.

7. Answer: D

Explanation: The correct answer is D. In the context of the passage, natural selection is described as a cornerstone of evolutionary theory, providing a framework for understanding how organisms adapt to their environments over time. The term "macroevolutionary mechanism" best encapsulates the overarching role of natural selection in driving large-scale evolutionary changes, such as speciation events and the emergence of new species.

Option A is incorrect because while genetic accumulation may occur as a result of natural selection, it does not capture the broader framework provided by natural selection in evolutionary theory. Option B is incorrect because while natural selection can lead to ecological specialization within populations, it does not fully encompass the overarching framework provided by natural selection in evolutionary theory. Option C is incorrect because while phenotypic adaptation is a consequence of natural selection, it does not fully encapsulate the broader framework provided by natural selection in evolutionary theory.

8. Answer: C

Explanation: The correct answer is C. In the context of the passage, "microevolutionary changes" refer to gradual alterations in the genetic composition of populations over time. These changes result from the accumulation of beneficial genetic variations within populations, driven by natural selection acting on the variation present within populations. Therefore, option C best represents the implied meaning of the phrase "microevolutionary changes."

9. Answer: B

Explanation: This is an Insert Text question where you are required to select the appropriate place to insert the provided sentence within the passage. Among the four possible answer choices provided in paragraph 4, the sentence "The book provided a thorough explanation of the concept of natural selection" is most fittingly inserted in choice B. The sentence following choice B elaborates on "Darwin’s work on natural selection."

Choices A, C, and D are incorrect because the surrounding sentences before and after each of these options primarily do not discuss the main idea presented in the sentence..

10. Answer: A, C, E

Explanation: This is a Prose Summary question, and the correct responses are A, C, and E. Therefore, options B, D, and F are incorrect.

Choice A: This choice accurately reflects a key idea from the passage, emphasizing the role of natural selection in shaping the survival and reproduction rates of individuals based on their genetic makeup and environmental interactions.

Choice C: This choice highlights another crucial aspect of natural selection, which involves the proliferation of advantageous genetic traits within populations over time, potentially leading to evolutionary changes and the emergence of new species.

Choice E: This choice contrasts natural selection with artificial selection, reinforcing the idea that natural selection operates without deliberate human intervention, in contrast to the intentional breeding practices involved in artificial selection.

Choice B: Choice B, "Charles Darwin popularized the term, distinguishing it from intentional artificial selection," is incorrect because this choice mentions Charles Darwin's role in popularizing the term "natural selection," but it does not directly align with the key ideas of the passage regarding how natural selection operates.

Choice D: Choice D, "It's important to note that natural selection occurs across all organisms, including both plants and animals," is incorrect because while the passage does mention that natural selection occurs across all organisms, this idea is not as central to the main points of the passage as the concepts reflected in the correct choices.

Choice F: Choice F, "Natural selection, not random genetic drift, primarily explains adaptive evolution," is incorrect because this choice contrasts natural selection with random genetic drift, which is mentioned in the passage, but it does not directly represent one of the key ideas regarding how natural selection operates and its implications for evolution.

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