ACT Reading : Analyzing Sequence in Natural Science Passages
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Example Question #11 : Understanding Organization And Argument In Natural Science Passages
Adapted from "Taking a Second Look: An Analysis of Genetic Markers in Species Relatedness" by Joseph Ritchie (2014)
Phylogenetics is the study of genetic composition in various species and is used by evolutionary biologists to investigate similarities in the molecular sequences of proteins in varying organisms. The amino acid sequences that build proteins are used to construct mathematical matrices that aid in determining evolutionary ties through the investigation of percentage similarities. The study of these matrices helps to expose evolutionary relationships between species that may not have the same overt characteristics.
Species adapt and evolve based on the pressures that exist in their environment. Climate, food source, and habitat availability are only a few factors that act on species adaptation. These stressors can alter the physical characteristics of organisms. This divergence in evolution has made it difficult to determine the interrelatedness of organisms by analyzing their physical characteristics alone.
For instance, looking only at physical characteristics, the ghost bat resembles a pigeon more than a spider monkey; however, phylogenetics has found that the amino acid sequences that construct the beta hemoglobin molecules of bats are twenty percent more similar to those of mammalian primates than those of birds. This helps reject the assumption that common physical characteristics between species are all that is needed to determine relatedness.
The differences produced by divergent evolution observed in the forest-dwelling, arboreal spider monkey and the nocturnal, airborne ghost bat can be reconciled through homology. Homologous characteristics are anatomical traits that are similar in two or more different species. For instance, the bone structure of a spider monkey’s wrist and fingers greatly resembles that of a bat’s wing or even a whale’s fin. These similarities are reinforced by phylogenetic evidence that supports the idea that physically dissimilar species can be evolutionarily related through anatomical and genetic similarities.
Paragraph four of the passage discusses which of the following?
the unreliability of physical characteristics in determining species relatedness.
the physiological functions of the spider monkey’s wrist and fingers, the bat’s wing, and the whale’s fin.
the theory of evolution.
the reasons why a spider monkey’s wrist and fingers can resemble a bat's wing or a whale's fin.
the reasons why a spider monkey’s wrist and fingers can resemble a bat's wing or a whale's fin.
One of paragraph four's central purposes is to give examples of homologous adaptation. It describes how the features of different species can possess anatomical similarities, even if the species are from vastly different habitats. The passage does not discuss the theory of evolution nor the physiological purposes of certain appendages, and the third paragraph, not the fourth, discusses the unreliability of physical characteristics in determining species relatedness.
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