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, so 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 zone 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.

Question

Prepp Team · Accepted Answer

Sentence Ordering: Understanding Life Form Dominance Over Geological Periods

This question requires us to arrange four jumbled sentences (P, Q, R, S) to form a coherent paragraph between the fixed first sentence (S1) and the last sentence (S6). The passage discusses how dominant life forms change across different geological periods due to evolutionary processes.

Analyzing the Fixed Sentences

S1: Establishes the core idea that geological periods are characterized by dominant life forms, which change as conditions evolve into new periods.

S6: Concludes that the creation of entirely new biological systems is infrequent, leading to only a limited number of major evolutionary developments throughout life's history.

Analyzing the Jumbled Sentences

P: Focuses on the prerequisites for individual evolutionary shifts, mentioning opportunity, ecological access, and new adaptations.
Q: Describes the characteristics of these shifts (rapid, followed by adaptive radiation) and provides an example (life on land).
R: Explains the mechanism within a geological period – natural selection drives experiments, leading to a breakthrough biological system that enables transition to the next period.
S: Highlights the dependency and progressive nature of evolutionary shifts, stating that breakthroughs build upon previous ones.

Constructing the Logical Flow (RSPQ)

Let's assemble the sentences logically:

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. (Introduces the concept of changing dominant life forms across geological periods.)
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. (Explains the process within a period – natural selection leading to a breakthrough system that allows the transition mentioned in S1.)
S: Every breakthrough of shift in dominance is dependent on ones that have occurred before so that the process of evolution is progressive. (Builds upon the 'breakthrough' concept from R, emphasizing that these evolutionary changes are sequential and build upon prior developments, making evolution progressive.)
P: Individual shifts rely on opportunity, ecological access, and the development of a new adaptation. (Details the factors necessary for these individual evolutionary 'shifts' or 'breakthroughs' mentioned previously.)
Q: Characteristically these shifts are rapid and are followed by a bout of adaptive radiation into the new ecological zone for example, with the emergence of life on land. (Describes the typical nature of these shifts – rapid progression and subsequent diversification (adaptive radiation) – and provides a concrete example.)
S6: The origin of completely new biological systems is comparatively rare, so consequently only a few major types have developed during the history of life. (Provides a concluding perspective, reinforcing the significance of these major shifts mentioned throughout the passage by noting their relative rarity.)

Final Coherent Paragraph

The sequence RSPQ creates a logical flow. It starts with the mechanism of change (R), discusses the progressive and dependent nature of these changes (S), outlines the conditions required for shifts (P), describes their characteristics and provides an example (Q), ultimately leading to the conclusion about the rarity of major evolutionary developments (S6).

Therefore, the correct order is RSPQ.