Since the Time of Darwin, Morphological Structures have been used to Identify Phylogenetic Relations.

Reading Passage Question

Since the time of Darwin, morphological structures have been used to identify phylogenetic relations. For example, the similarity between a man‘s arm and a bat‘s wing is taken as evidence of their common origin. There are innumerable examples of this in nature. From the whiskers of lions and domestic cats to the bone structure in the fins of a whale and that of a human hand, it seems one would be hard pressed to fine an attribute in a particular species that did not illustrate some kind of relationship to another species.

Similarities in behaviour patterns can also serve in reconstructing evolutionary history. It is not always clear, however, how certain types of innate behaviour evolved through natural selection. In its modern form the Darwinian interpretation of evolution asserts that evolution consists of changes in the frequency of appearance of different genes in populations, and that the frequency of the appearance of a particular gene can only increase if the gene increases the "Darwinian fitness" (the expected number of surviving offspring) of its possessors.

The discovery of a genetic predisposition to be especially responsive to certain stimuli was an important contribution to the study of evolution. Genetically determined responses must be subject to the pressures of natural selection. Hence innate behaviour must evolve. Ethologists were able to show how a motor pattern employed in a noncommunicatory context such as feeding could evolve into a ritualized form employed as a signal in, say, courtship.

Differentiation in innate behaviour patterns could be traced to selection pressures arising from the environment. There are many instances of animal behaviour patterns that seem not to contribute to the survival of the individual displaying that behaviour. The classic example is the behaviour of the worker bee: this insect will sting an intruder and thereby kill itself in defense of the hive. The problem is evident: How can a gene that makes suicide more likely become established? The concern over this type and other types of apparently anomalous behaviour led to the development of a new phase in the study of the evolution of behaviour: a marriage of ethology and population genetics.

Animal behaviour was formerly thought to consist of simple responses, some of them innate and some of them learned, to incoming stimuli. Complex behaviour, if it was considered at all, was assumed to be the result of complex stimuli. Over the past 60 years, however, a group of ethologists, notably Konrad Lorenz, Nikolaas Tinbergen and Karl von Frisch, have established a new view of animal behaviour. Studying whole patterns of innate animal behaviour in natural environments (rather tha focusing primarily on learned behaviour, as animal behaviourists do), they have shown that the animal brain possesses certain specific competences, that animals have an innate capacity for performing complex acts in response to simple stimuli. As Gould put it in 1982, "Rather than encompassing merely the rigid and impoverished behavioural repertoire of primitive organisms, instinct has been shown to possess a stunning flexibility and overwhelming richness. As a result, we no longer need to invoke the barren behaviouristic tenet of learning as an 'explanation‘ of complexity."

Source:RC99

“Since the time of Darwin, morphological structures have been used to identify phylogenetic relations.”- is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.

This GMAT Reading Comprehension consists of 3 comprehension questions. The GMAT Reading Comprehension questions are designed for the purpose of testing candidates’ abilities in understanding, analyzing, and applying information or concepts. Candidates can actively prepare with the help of GMAT Reading Comprehension Practice Questions.

Solution and Explanation

Question1
In the context of the arguments being made by the author in this passage, the term "phylogenetic" (line 2) most closely means:

1. structural.
2. inter-species.
3. innate.
4. functional.
5. acquired

Question 2
Which of the following scenarios would be most analogous to the example given by the author of the worker bee?

1. A male spider reacts to intruding predators by releasing venom that kills both the predator and itself.
2. A female marsupial abandons her weakest offspring as prey for her natural enemies in order to protect the rest of her brood.
3. The youngest member of a canine pack sacrifices himself by fatally wounding an attacking predator so that the pack itself can escape.
4. A drone ant kills an insect preying on his collective by stinging the insect‘s eyes.
5. A young Cheetah tries to hunt and fails repeatedly

Question 3
The author of the passage would be most likely to agree with which of the following statements?

1. Unusual animal behaviours can be understood in terms of natural selection when they are studied in the context of procreation patterns and needs for survival of that particular species.
2. Overpopulated animal colonies often weed out their excess or weak members by abandoning them to their natural predators.
3. Darwin‘s evolutionary theories of natural selection have been unnecessarily modified by modern scientists in order to make them accord with bservations of animal behaviour patterns.
4. The evolution of certain types of innate animal behaviour demonstrate the inadequacy of the notion of "Darwinian fitness" as an approach to studying evolution.
5. There are some natural phenomena that cannot be explained by logic

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