Charles Darwin objected to all attempts to reduce his theory of evolut

Charles Darwin objected to all attempts to reduce
his theory of evolution to its doctrine of natural
selection. “Natural selection has been the main but not
the exclusive means of modification,” he declared.
(5) Nonetheless, a group of self-proclaimed strict
constructionist Darwinians has recently risen to
prominence by reducing Darwin’s theory in just this
way. These theorists use the mechanism of natural
selection to explain all biological phenomena; they
(10) assert that natural selection is responsible for every
aspect of every species’ form and behavior, and for
the success or failure of species in general.

Natural selection is generally held to result in
adaptation, the shaping of an organism’s form and
(15) behavior in response to environmental conditions to
achieve enhanced reproductive success. If the strict
constructionists are right, the persistence of every
attribute and the survival of every species are due to
such adaptation. But in fact, nature provides numerous
(20) examples of attributes that are not adaptations for
reproductive success and of species whose success or
failure had little to do with their adaptations.

For example, while it is true that some random
mutations of genetic material produce attributes that
(25) enhance reproductive success and are thus favored by
natural selection, and others produce harmful attributes
that are weeded out, we now know from population
genetics that most mutations fall into neither category.
Research has revealed that neutral, nonadaptive
(30) changes account to a large extent for the evolution of
DNA. Most substitutions of one unit of DNA for
another within a population have no effect on
reproductive success. These alterations often change
the attributes of species, but their persistence from
(35) one generation to the next is not explainable by
natural selection.

Additionally, the study of mass extinctions in
paleontology has undermined the strict constructionist
claim that natural selection can account for every
(40) species’ success or failure. The extinction of the
dinosaurs some 65 million years ago was probably
caused by the impact of an extraterrestrial body.
Smaller animal species are generally better able to
survive the catastrophic changes in climate that we
(45) would expect to follow from such an impact, and
mammals in the Cretaceous period were quite small
because they could not compete on the large scale of
the dominant dinosaurs. But while this scenario
explains why dinosaurs died off and mammals fared
(50) relatively well, it does not conform to the strict
constructionist view of the adaptive reasons for the
success of species. For that view assumes that
adaptations are a response to conditions that are
already in place at the time the adaptations occur,
(55) and mammals could not have adapted in advance to
conditions caused by the impact. In a sense, their
success was the result of dumb luck.

1. Which one of the following most accurately expresses the main point of the passage?

(A) Evidence from two areas of science undermines the strict constructionist claim that natural selection is the only driving force behind evolution.
(B) According to strict constructionist Darwinians, new evidence suggests that natural selection is responsible for the failure of most extinct species.
(C) New evidence demonstrates that natural selection can produce nonadaptive as well as adaptive changes.
(D) Strict constructionist followers of Darwin maintain that natural selection is responsible for all evolutionary change.
(E) Evidence from the study of population genetics helps to disprove the claim that natural selection results in the survival of the fittest species.


2. According to the author, mammals were able to survive catastrophic environmental changes that occurred roughly 65 million years ago because they

(A) had adapted previously to similar changes
(B) were relatively small
(C) were highly intelligent
(D) lived in a wide range of environments
(E) were able to reproduce quickly


3. The author asserts which one of the following regarding mutations of genetic material?

(A) The majority of such mutations are not passed on to subsequent generations.
(B) The majority of such mutations occur during periods when mass extinctions take place.
(C) The majority of such mutations change species’ behavior rather than their appearance.
(D) The majority of such mutations have no effect on reproductive success.
(E) The majority of such mutations occur in larger rather than smaller species.


4. The author would be most likely to agree with which one of the following statements?

(A) Natural selection is responsible for almost none of the characteristics of existing species.
(B) The fact that a species flourishes in a certain environment is not proof of its adaptation to that environment.
(C) Only evolutionary changes that provide some advantage to a species are transmitted to subsequent generations.
(D) Large animal species are generally unable to survive in harsh environmental conditions.
(E) Natural selection is useful for explaining the form but not the behavior of most species.


5. The author’s stance toward the arguments of the strict constructionist Darwinians can most accurately be described as one of

(A) emphatic disagreement
(B) mild disapproval
(C) open-minded neutrality
(D) conditional agreement
(E) unreserved endorsement


6. Which one of the following most accurately and completely describes the function of the second paragraph of the passage?

(A) It outlines the objections to traditional evolutionary theory raised by the strict constructionists mentioned in the first paragraph.
(B) It lists recent evidence suggesting that the strict constructionist claims described in the first paragraph are incorrect.
(C) It describes the strict constructionists’ view of evolutionary theory in order to explain why the evidence described in subsequent paragraphs has recently gotten so much attention.
(D) It enumerates the arguments for the strict constructionist position that are rebutted in the paragraphs that follow.
(E) It explains the ramifications of the strict constructionists’ claims and helps clarify the relevance of evidence offered in subsequent paragraphs.


7. The primary purpose of the passage is to

(A) argue in favor of a recently proposed hypothesis
(B) summarize a contemporary debate
(C) demonstrate that a particular view is incorrect
(D) criticize the proponents of a traditional theory
(E) explain why a particular theory is gaining popularity