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Over the years, biologists have suggested two main pathways by which
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10 May 2021, 11:11
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Over the years, biologists have suggested two main pathways by which sexual selection may have shaped the evolution of male birdsong. In the first, male competition and intrasexual selection produce relatively short, simple songs used mainly in territorial behavior. In the second, female choice and intersexual selection produce longer, more complicated songs used mainly in mate attraction; like such visual ornamentation as the peacock's tail, elaborate vocal characteristics increase the male's chances of being chosen as a mate, and he thus enjoys more reproductive success than his less ostentatious rivals. The two pathways are not mutually exclusive, and we can expect to find examples that reflect their interaction. Teasing them apart has been an important challenge to evolutionary biologists.
Early research confirmed the role of intrasexual selection. In a variety of experiments in the field, males responded aggressively to recorded songs by exhibiting territorial behavior near the speakers. The breakthrough for research into intersexual selection came in the development of a new technique for investigating female response in the laboratory. When female cowbirds raised in isolation in soundproof chambers were exposed to recordings of male song, they responded by exhibiting mating behavior. By quantifying the responses, researchers were able to determine what particular features of the song were most important. In further experiments on song sparrows, researchers found that when exposed to a single song type repeated several times or to a repertoire of different song types, females responded more to the latter. The beauty of the experimental design is that it effectively rules out confounding variables; acoustic isolation assures that the female can respond only to the song structure itself.
If intersexual selection operates as theorized, males with more complicated songs should not only attract females more readily but should also enjoy greater reproductive success. At first, however, researchers doing fieldwork with song sparrows found no correlation between larger repertoires and early mating, which has been shown to be one indicator of reproductive success; further, common measures of male quality used to predict reproductive success, such as weight, size, age, and territory, also failed to correlate with song complexity.
The confirmation researchers had been seeking was finally achieved in studies involving two varieties of warblers. Unlike the song sparrow, which repeats one of its several song types in bouts before switching to another, the warbler continuously composes much longer and more variable songs without repetition. For the first time, researchers found a significant correlation between repertoire size and early mating, and they discovered further that repertoire size had a more significant effect than any other measure of male quality on the number of young produced. The evidence suggests that warblers use their extremely elaborate songs primarily to attract females, clearly confirming the effect of intersexual selection on the evolution of birdsong.
Question 1
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63% (03:30) correct
38% (03:30) wrong based on 32 sessions
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1) The passage is primarily concerned with
(A) showing that intrasexual selection has a greater effect on birdsong than does intersexual selection (B) contrasting the role of song complexity in several species of birds (C) describing research confirming the suspected relationship between intersexual selection and the complexity of birdsong (D) demonstrating the superiority of laboratory work over field studies in evolutionary biology (E) illustrating the effectiveness of a particular approach to experimental design in evolutionary biology
Question 2
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2) The author mentions the peacock's tail most probably in order to
(A) cite an exception to the theory of the relationship between intrasexual selection and male competition (B) illustrate the importance of both of the pathways that shaped the evolution of birdsong (C) draw a distinction between competing theories of intersexual selection (D) give an example of a feature that may have evolved through intersexual selection by female choice (E) refute a commonly held assumption about the role of song in mate attraction
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3) According to the passage, which of the following is specifically related to intrasexual selection?
(A) Female choice (B) Territorial behavior (C) Complex song types (D) Large song repertoires (E) Visual ornamentation
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4) Which of the following, if true, would most clearly demonstrate the interaction mentioned in lines red?
(A) Female larks respond similarly both to short, simple songs and to longer, more complicated songs. (B) Male canaries use visual ornamentation as well as elaborate song repertoires for mate attraction. (C) Both male and female blackbirds develop elaborate visual and vocal characteristics. (D) Male jays use songs to compete among themselves and to attract females. (E) Male robins with elaborate visual ornamentation have as much reproductive success as rivals with elaborate vocal characteristics.
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5) The passage indicates that researchers raised female cowbirds in acoustic isolation in order to
(A) eliminate confounding variables (B) approximate field conditions (C) measure reproductive success (D) quantify repertoire complexity (E) prevent early mating
Question 6
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6) According to the passage, the song sparrow is unlike the warbler in that the song sparrow
(A) uses songs mainly in territorial behavior (B) continuously composes long and complex songs (C) has a much larger song repertoire (D) repeats one song type before switching to another (E) responds aggressively to recorded songs
Question 7
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7) The passage suggests that the song sparrow experiments mentioned in lines blue failed to confirm the role of intersexual selection because
(A) females were allowed to respond only to the song structure (B) song sparrows are unlike other species of birds (C) the experiments provided no evidence that elaborate songs increased male reproductive success (D) the experiments included the songs of only a small number of different song sparrows (E) the experiments duplicated some of the limitations of previous field studies
Re: Over the years, biologists have suggested two main pathways by which
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14 May 2021, 07:53
4
Spent approx 13mins. All correct.
Passage talks about 2 pathways how birdsong is related to Sexual selection. Both ways are somehow related. Then, One pathway is stated and backed up by the research. Other pathway has different result from the research. Other research links both the pathways.
1) The passage is primarily concerned with (This is main idea question. Hence specific answer choice are incorrect)
(A) showing that intrasexual selection has a greater effect on birdsong than does intersexual selection - out of scope. Nowhere it is stated that which selection is better. (B) contrasting the role of song complexity in several species of birds - too specific (C) describing research confirming the suspected relationship between intersexual selection and the complexity of birdsong - that's that main idea. (D) demonstrating the superiority of laboratory work over field studies in evolutionary biology - out of scope. (E) illustrating the effectiveness of a particular approach to experimental design in evolutionary biology - out of scope.
2) The author mentions the peacock's tail most probably in order to (This is an inference question. This is stated in first para)
(A) cite an exception to the theory of the relationship between intrasexual selection and male competition - out of scope (B) illustrate the importance of both of the pathways that shaped the evolution of birdsong - only for the 2nd is stated (C) draw a distinction between competing theories of intersexual selection - out of scope (D) give an example of a feature that may have evolved through intersexual selection by female choice - Yes, example of 2nd pathway (E) refute a commonly held assumption about the role of song in mate attraction - out of scope
3) According to the passage, which of the following is specifically related to intrasexual selection? (1st pathway)
(A) Female choice - out of scope (B) Territorial behavior - stated in 2nd para. (C) Complex song types - out of scope. It is stated for 2nd pathway. (D) Large song repertoires - out of scope. It is stated for 2nd pathway. (E) Visual ornamentation - out of scope. It is stated for 2nd pathway.
4) Which of the following, if true, would most clearly demonstrate the interaction mentioned in lines red?
Red line says that both the pathways are somehow related. After reading the whole passage, both the pathways are related with songs.
(A) Female larks respond similarly both to short, simple songs and to longer, more complicated songs. - Inconsistent as there is no similarity on highlighted. (B) Male canaries use visual ornamentation as well as elaborate song repertoires for mate attraction. - Out of scope as it says only about 2nd pathway. (C) Both male and female blackbirds develop elaborate visual and vocal characteristics. - Out of scope as it is only for 2nd pathway. (D) Male jays use songs to compete among themselves and to attract females. - That's the similarity between both the patways. (E) Male robins with elaborate visual ornamentation have as much reproductive success as rivals with elaborate vocal characteristics. - out of scope.
5) The passage indicates that researchers raised female cowbirds in acoustic isolation in order to
The beauty of the experimental design is that it effectively rules out confounding variables
(A) eliminate confounding variables - Yes (B) approximate field conditions. Out of scope. (C) measure reproductive success. Out of scope. (D) quantify repertoire complexity. Out of scope. (E) prevent early mating. Out of scope
6) According to the passage, the song sparrow is unlike the warbler in that the song sparrow
We need to compare the research of 1st pathway with the research of 2nd pathway.
(A) uses songs mainly in territorial behavior - Inconsistent as it is only for 1st pathway. (B) continuously composes long and complex songs - Inconsistent as it is only for 2nd pathway. (C) has a much larger song repertoire. Inconsistent as it is only for 2nd pathway. (D) repeats one song type before switching to another. Song sparrow repeats while Warbler does not. (E) responds aggressively to recorded songs. Inconsistent as it is only for 1st pathway.
7) The passage suggests that the song sparrow experiments mentioned in lines blue failed to confirm the role of intersexual selection because
How Song sparrow research is not consistent with 2nd pathway.
(A) females were allowed to respond only to the song structure. Inconsistent. Only for 1st pathway. (B) song sparrows are unlike other species of birds. Out of scope. (C) the experiments provided no evidence that elaborate songs increased male reproductive success. Yes, song sparrows found no correlation between larger repertoires and early mating. (D) the experiments included the songs of only a small number of different song sparrows. Out of scope. (E) the experiments duplicated some of the limitations of previous field studies. Out of scope.
10 May 2021, 11:11
63% (03:30) correct
