S1. Every geological period has been dominated by one particular form of life; as conditions changed to those of a new period, different types of organisms emerged into dominance. S6. The origin of completely new biological systems is comparatively rare, consequently only a few major types have developed during the history of life. P. Individual shifts rely on opportunity, ecological access, and the development of a new adaptation. Q. Characteristically these shifts are rapid and are followed by a bout of adaptive radiation into the new ecological - for example, with the emergence of life on land. R. Within each period, natural selection has created a vast array of adaptive experiments culminating in a breakthrough to a new biological system that may cross the ecological barrier to the next period. S. Every breakthrough of shift in dominance is dependent on ones that have occurred before so that the process of evolution is progressive.

Directions: In this section, each item consists of six sentences of a passage. The first and sixth sentences are given in the beginning as S1 and S6. The middle four sentences in each have been jumbled up and labelled as P. Q. R, and S. You are required to find the proper sequence of these four sentences and mark your response accordingly on the Answer Sheet.

1. A. PQSR
2. B. QSPR
3. C. RSPQ ✓
4. D. RQPS

Correct Answer: C. RSPQ

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