Para 1 Summary – Author introduces a phenomenon and why researchers believe in latitude gradient so.
Para 2 Summary – In this para author refers to one ‘time theory’ to explain and mentions a paradox.
Para 3 Summary – Another approach is presented with positive correlations but untested ones.
Para 4 Summary – A third theory explain climatic stability as a factor to explain the phenomenon.
Para 5 Summary – Author opines that the fourth hypothesis is the most credible.
Para 6 Summary – Finally author presents the details of the fourth hypothesis and gives reasons why it is so.
Summary – Author introduces a phenomenon and provides our different hypothesis with one being most credible.
1. Which one of the following most accurately expresses the main idea of the passage?(A) At present, no single hypothesis explaining the latitudinal gradient in numbers of species is more widely accepted than any other. – WRONG. It goes to extreme in saying that no hypothesis is accepted though passage mentions one is most acceptable looking.
(B) The tropical climate is more conducive to promoting species diversity than are arctic or temperate climates. – WRONG. Limited scope. Only one paragraph covers the scope mentioned.
(C) Several explanations have been suggested for global patterns in species distribution, but a hypothesis involving rates of speciation seems most promising. –
CORRECT. Out of all theories presented one is most suitable.(D) Despite their differences, the various hypotheses regarding a latitudinal gradient in species diversity concur in predicting that the gradient can be expected to increase.- WRONG. Similar problem as that o option B. Limited scope.
(E) In distinguishing among the current hypotheses for distribution of species, the most important criterion is whether a hypothesis proposes a mechanism that can be tested and validated. – WRONG. Irrelevant. Nowhere such claim mentioned by author.
2. Which one of the following situations is most consistent with the species-energy hypothesis as described in the passage?Answering the question requires a proper understanding of that part of passage.
(A) The many plants in a large agricultural tract represent a limited range of species. – WRONG. Species energy and range correlation is not discussed anywhere n the passage.
(B) An animal species experiences a death rate almost as rapid as its rate of growth and reproduction. – WRONG. Death rate is not discussed in the passage. Though the option is close.
(C) Within the small number of living organisms in a desert habitat, many different species are represented. – WRONG. Similar to option A this one suffers from drawing incorrect correlation.
(D) In a tropical rain forest, a species with a large population is found to exhibit instances of local extinction. – WRONG. It goes opposite to what one of the theories in the passage claims.
(E) In an arctic tundra, the plants and animals exhibit a slow rate of growth and reproduction. –
CORRECT. Initially, though got stuck between this option and B but as reasoned in B eliminated it and chose E. Also here only growth and reproduction is discussed i.e. within scope. 3. As presented in the passage, the principles of the time theory most strongly support which one of the following predictions?This is a must be true/inference type of question. Though got it WRONG in timed situation and marked D after POE. (A) In the absence of additional ice ages, the number of species at high latitudes could eventually increase significantly. – CORRECT. Ice ages have affected arctic a lot and hence less number of species. On the other side, had this not been the case i.e. had ice ages not affected the arctic region it would have had high number of species.
(B) No future ice ages are likely to change the climatic conditions that currently characterize temperate regions. – WRONG. ‘Time theory’ concerns species not climatic conditions only since species adapt to them.
(C) If no further ice ages occur, climatic conditions at high latitudes might eventually resemble those at today’s tropical latitudes. WRONG. Again same issues as that o option ‘B’.
(D) Researchers will continue to find many more new species in the tropics than in the arctic and temperate zones. –
WRONG. Marked this option correct with an understanding that since species have more time to adapt in tropics than arctic and temperate zones, researchers would find many species, but that’s not the case here. Instead the option goes a little more out of scope when it says that ‘many more species’ would be found. How many is not mentioned in this theory. (E) Future ice ages are likely to interrupt the climatic conditions that now characterize high-latitude regions. – WRONG. It may be true but what about species. It does not talk about them.
4. Which one of the following, if true, most clearly weakens the rate-of-speciation hypothesis as it is described in the passage?A clear understanding of paragraphs 5 and 6 can help find the answer here.
(A) A remote subgroup of a tropical species is reunited with the original population and proves unable to interbreed with members of this original population. – WRONG. It strengthens the rate-of-speciation hypothesis by claiming similar results as mentioned in the theory.
(B) Investigation of a small area of a tropical rain forest reveals that many competing species are able to coexist on the same range of resources. – WRONG. Neither weakens nor strengthens the rate-of-speciation hypothesis. Rate-of-speciation hypothesis does not mentioned competing species.
(C) A correlation between higher energy influx, larger populations, and lower probability of local extinction is definitively established. – WRONG. Larger population and energy nlux s part of species – energy theory.
(D) Researchers find more undiscovered species during an investigation of an arctic region than they had anticipated. – WRONG. This is close to the answer but undiscovered species are not new species.
(E) Most of the isolated subgroups of mammalian life within a tropical zone are found to experience rapid extinction. –
CORRECT. Rapid extinction in tropics is exactly opposite to the rate-of-speciation hypothesis’s claim hence correct. 5. Which one of the following inferences about the biological characteristics of a temperate-zone grassland is most strongly supported by the passage?Marked B which is WRONG after POE between ‘B’ and ‘D’. Again a proper understanding of passage would help to answer the question. (A) It has more different species than does a tropical-zone forest. – WRONG. Tropical zone forest would have most different species. Refer paragraph 4 which states that tropic climate’s stability is the reason behind coexistence of various species.
(B) Its climatic conditions have been severely interrupted in the past by a succession of ice ages. –
WRONG. ‘Severely’ is opposite to ‘less’ as mentioned in Para 2 – Time theory.(C) If it has a large amount of biomass, it also has a large number of different species. – WRONG. Though it refers to untested mechanism(refer para 3), it draws a negative correlation.
(D) It has a larger regional pool of species than does an arctic grassland. – CORRECT. Since arctic would have least latitude gradient and tropics the most, temperate would have better than arctic, thus larger regional pool. In timed situation however, eliminated it.
(E) If population groups become isolated at its edges, they are likely to adapt to local conditions and become new species. – WRONG. Inference is true for tropics but for temperate it can’t be established. Refer Para 2 and 4 combined.
6. With which one of the following statements concerning possible explanations for the latitudinal gradient in number of species would the author be most likely to agree?Marked D which is WRONG. Again a must be true/inference type question. It states that author most likely agrees with the following options when used to explain the latitudinal gradient in terms of number of species. May be this is the toughest among all.
(A) The time theory is the least plausible of proposed hypotheses, since it does not correctly assess the impact of ice ages upon tropical conditions. – WRONG. Time theory does mention the difference between tropics and temperate/arctic and thus latitudinal gradient. Impact of Ice ages is not factor here so incorrect.
(B) The rate-of-speciation hypothesis addresses a principal objection to the climatic-stability hypothesis. – CORRECT. In para 4 the statement ‘ecology of local communities cannot account for the origin of the latitudinal gradient’ raises a limitation to explain which para 6 elaborates using ‘small populations spread out and formation of isolated groups’ explains latitudinal gradient.
(C) The major objection to the time theory is that it does not accurately reflect the degree to which the latitudinal gradient exists, especially when undiscovered species are taken into account. – WRONG. Author would disagree here since nowhere he/she is concerned with the accuracy aspect of latitudinal gradient using time theory. Author does mention in the intro about ‘undiscovered species’ that are believed to be living in arctic and also never opines about ‘Time theory’.
(D) Despite the claims of the species-energy hypothesis, a high rate of biological growth and reproduction is more likely to exist with low biomass than with high biomass. –
WRONG. Marked this option correct since the question looks more convoluted and author agrees with species-energy hypothesis. But how would author disagree with this option I am still unclear.(E) An important advantage of the rate-of-speciation theory is that it considers species competition in a regional rather than local context. – WRONG. Though initially confused about this option, since author would disagree with this option. However in the last line of the passage ‘Since subgroups in an arctic environment are more likely to face extinction than those in the tropics, the latter are more likely to survive long enough to adapt to local conditions and ultimately become new species’ author provides enough reasons that population difference (latitudinal gradient) would exist between arctic and tropic.
Have still doubt on last question. Waiting for experts’ explanation on this answer.
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Pain + Reflection = Progress | Ray Dalio
Good Books to read prior to MBA