In the mid-1960s, the biologist Paul Ehrlich - author of The Population Bomb (1968) - and his Stanford University colleague Peter Raven challenged Mayr's ideas about speciation. They had studied checkerspot butterflies living in the Jasper Ridge Biological Preserve in California, and it soon became clear that they were not examining a single population. Through years of capturing, marking and then recapturing the butterflies, they were able to prove that within the population, spread over just 50 acres of suitable checkerspot habitat, there were three groups that rarely interacted despite their very close proximity.
Among other ideas, Ehrlich and Raven argued in a now classic paper from 1969 that gene flow was not as predictable and ubiquitous as Mayr and his cohort maintained, and thus evolutionary divergence between neighboring groups in a population was probably common. They also asserted that isolation and gene flow were less important to evolutionary divergence than natural selection (when factors such as mate choice, weather, disease or predation cause better-adapted individuals to survive and pass on their successful genetic traits). For example, Ehrlich and Raven suggested that, without the force of natural selection, an isolated population would remain unchanged and that, in other scenarios, natural selection could be strong enough to overpower gene flow...
Which of the following best sums up Ehrlich and Raven's argument in their classic 1969 paper?
- Ernst Mayr was wrong in identifying physical separation as the cause of species diversity
- Checkerspot butterflies in the 50-acre Jasper Ridge Preserve formed three groups that rarely interacted with each other
- While a factor, isolation was not as important to speciation as natural selection
- Gene flow is less common and more erratic than Mayr and his colleagues claimed.
The Correct Option is C
Solution and Explanation
Option (1) is intricate as it fails to directly address the core issue – if Mayr was incorrect, what was the correct perspective? Ehrlich and Raven's argument is not clear. Similarly, (2) provides evidence but lacks a clear thesis statement. The ideal approach is to express your viewpoint on the topic directly and concisely in one sentence. Although (4) comes close by referencing "gene flow," the answer is (3) – as indicated in the third paragraph - where it is stated that "isolation and gene flow were less important to evolutionary divergence than natural selection." Therefore, the correct answer is (3).
All of the following statements are true according to the passage EXCEPT
- Gene flow contributes to evolutionary divergence
- The Population Bomb questioned dominant ideas about species diversity
- Evolutionary changes unfold imperceptibly over time.
- Checkerspot butterflies are known to exhibit speciation while living in close proximity
The Correct Option is B
Solution and Explanation
Ehrlich and Raven acknowledge in the third paragraph that gene flow contributes to evolutionary divergence, stating, "isolation and gene flow were less important to evolutionary divergence than natural selection," indicating that isolation and gene flow have some importance in evolutionary divergence. This point is also reiterated in the last sentence of the passage. Therefore, (2) is the correct choice. Additionally, (3) is supported by information in the first paragraph, mentioning the separation of populations over geologic scales of time. Furthermore, (4) finds support in the second paragraph, which describes three groups that rarely interacted despite their close proximity.
The author discusses Mayr, Ehrlich and Raven to demonstrate that
- evolution is a sensitive and controversial topic
- Ehrlich and Raven's ideas about evolutionary divergence are widely accepted by scientists.
- the causes of speciation are debated by scientists
- checkerspot butterflies offer the best example of Ehrlich and Raven's ideas about speciation
The Correct Option is C
Solution and Explanation
The passage does not suggest that evolution is a sensitive or controversial topic, so (1) is eliminated. The determination of whether Ehrlich and Raven's thesis superseded Mayr's is not made in the passage, ruling out (2). The merits of checkerspot butterflies are not discussed in the passage, so (4) is also eliminated. The passage focuses on Mayr, Ehrlich, and Raven in the context of theories of speciation, making (3) the correct answer.
Top Questions on Reading Comprehension
Passage: Toru Dutt is considered the earliest Indian female writer in English. She travelled extensively in Europe from a young age with her family. She and her sister Aru became fascinated with Paris and French literature. In London, they came in contact with such august personages such as Sir Bartle Frere, the Gover- nor of Bombay from 1862 to 1867, and Sir Edward Ryan, the Chief Justice of the Supreme Court, Calcutta, from 1837 to 1843. Toru Dutt was greatly influenced in her writings by French Romantic poets like Victor Hugo and English writers like Elizabeth Browning, John Keats, Charlotte Bronte and Jane Austen. She was also intrigued by the legends and myths of India, and even learned Sanskrit. Her writings were marked by romantic melancholia and an obsession and preoccupation with death. This was partly due to her suffering and pain following the early tragic deaths of her siblings, especially her older sister Aru, with whom she was quite close. Her chosen subjects often portrayed separation, loneliness, captivity, dejec- tion, declining seasons and untimely death. She led an ”Ivory Tower existence” and her own death came quite early, at the age of 21, in the full bloom of her talent and on the eve of the awakening of her genius. Toru Dutt’s most famous work is A Sheaf Gleaned in French Fields, an anthology of poems translated from French to English. It also contained a few original poems that showcase her vast insight into French literature. She used to publish poems in the Bengal Magazine, under the pseudonym ”TD”. But most of her powerful work was published posthumously, in- cluding the French novel Le Journal de Mademoiselle D’Arvers and the unfinished English novel Bianca, or, the Young Spanish Maiden. Her work Ancient Ballads and Legends of Hindustan depicts a shrewd knowledge of Hindu mythology and an instinctive empathy with the conditions of life they represent. An assimilation of the Occident and the Orient nourished Toru’s poetic skills; in her, we find a tripartite influence of a French education, lectures at Cambridge and the study of Sanskrit literature.
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“Why do they pull down and do away with crooked streets, I wonder, which are my delight, and hurt no man living? Every day the wealthier nations are pulling down one or another in their capitals and their great towns: they do not know why they do it; neither do I. It ought to be enough, surely, to drive the great broad ways which commerce needs and which are the life-channels of a modern city, without destroying all history and all the humanity in between: the islands of the past.”
(From Hilaire Belloc’s “The Crooked Streets”)
Based only on the information provided in the above passage, which one of the following statements is true?- GATE PH - 2025
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“Why do they pull down and do away with crooked streets, I wonder, which are my delight, and hurt no man living? Every day the wealthier nations are pulling down one or another in their capitals and their great towns: they do not know why they do it; neither do I. It ought to be enough, surely, to drive the great broad ways which commerce needs and which are the life-channels of a modern city, without destroying all history and all the humanity in between: the islands of the past.” (From Hilaire Belloc’s “The Crooked Streets”)
Based only on the information provided in the above passage, which one of the following statements is true?
- GATE CE - 2025
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- “His life was divided between the books, his friends, and long walks. A solitary man, he worked at all hours without much method, and probably courted his fatal illness in this way. To his own name there is not much to show; but such was his liberality that he was continually helping others, and fruits of his erudition are widely scattered, and have gone to increase many a comparative stranger’s reputation.”
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Based only on the information provided in the above passage, which one of the following statements is true?- GATE CE - 2025
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- Read the excerpt from a Handicrafts Manual: ‘Advanced Knitting Techniques’ and answer the following questions by choosing the most appropriate answer.
THE FAIR ISLE METHOD: Fair Isle knitting is a traditional technique that involves using two or more colours of yarn in a single row to create intricate patterns and designs. This method requires careful tension management to ensure even stitches and prevent puckering. To begin, select your colours and cast on the desired number of stitches. As you knit, alternate between colours every few stitches, carrying the unused yarn along the back of the work. Mastering the Fair Isle technique allows you to create stunning visual effects in garments, accessories, and home textiles.
THE CONTINENTAL STYLE: The Continental knitting style, often referred to as “picking,” involves holding the yarn in the left hand while the right hand manipulates the needles. This method allows for greater speed and efficiency, particularly when working with complex patterns or multiple colours. To practice this style, start by casting on your stitches and using your left hand to tension the yarn. With each stitch, simply “pick” the yarn with your right needle, forming a quick and fluid motion. As you become comfortable with this technique, you may find that your overall knitting speed and comfort improve significantly.
THE SHORT-ROW TECHNIQUE: Short-row knitting is an advanced technique that allows for the creation of shaped garments, such as sleeves and shoulders, without the need for complex shaping. To make a sleeve using this technique, begin by casting on the required number of stitches. Work a portion of the row, then turn your work and return without completing the full row to create the “short rows” that shape the curves of the sleeve. To prevent holes at the turn, wrap the stitch before you turn your work. Repeat this process as needed to achieve the desired shaping and dimension of the sleeve. Once you have shaped the sleeve, you can then sew the side seams to connect the pieces of your garment and finally, complete the edges to ensure a clean finish. This method not only helps shape curves but also adds dimension to your piece, allowing you to enhance fit and style.- AILET BALLB (Hons.) - 2025
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