Deceptive Evolution | Science RC Practice

Can those ancient “living fossils” lurking in today’s swamps actually be evolution’s most dynamic success stories? What if creatures we dismiss as prehistoric relics are actually demonstrating nature’s most sophisticated adaptive strategies? These medium difficulty RC passages analyze how crocodiles have navigated millions of years of environmental upheaval.

Read these hard RC passage(s) in Science Technology and Environment and answer the question(s) that follows. You can choose the GMAT style Reading Passage and the question or the GRE RC variant and answer the GRE-style question. Even better, you could solve both.

GMAT Science RC | Medium Difficulty | ~220 words

Crocodiles have long been dismissed as evolutionary anachronisms—creatures that supposedly ceased meaningful adaptation millions of years ago and merely persist as “living fossils” in modern ecosystems. This characterization, however, represents a profound misinterpretation of crocodilian evolutionary dynamics, as demonstrated by recent morphometric research that tracked anatomical changes across multiple species over geological time scales. Researchers from University College London employed three-dimensional modeling to analyze skull landmarks in twenty-four contemporary crocodile species and nineteen fossil relatives, revealing accelerated evolutionary modifications occurring within the past two million years across Australia, Southeast Asia, and the Indo-Pacific regions.

The study’s findings directly contradict prevailing assumptions about crocodilian stasis. Modern species exhibit rapid convergence toward specific skull configurations not because they retain ancient characteristics, but because they repeatedly evolve specialized feeding mechanisms tailored to exploit particular prey categories. Fish-eating species develop elongated, narrow snouts equipped with numerous small teeth for capturing slippery aquatic prey, while broad-snouted species evolve powerful jaws designed for crushing turtle shells and large bones. Significantly, these adaptations emerge independently in geographically separated populations: contemporary saltwater crocodiles possess skull morphology nearly identical to extinct Madagascar species, despite minimal genetic relationship. Current crocodilian diversity encompasses merely one-third of historically documented skull variations, indicating that these reptiles continuously modify their anatomical architecture in response to environmental pressures rather than remaining evolutionary relics.

Question Type: Role of Sentence | Question Difficulty: Medium

The author compares contemporary saltwater crocodiles with extinct Madagascar species in order to:

1. Illustrate the geographic distribution of crocodilian species across different continents and time periods
2. Provide evidence that morphological similarities result from independent evolutionary adaptation rather than shared ancestry
3. Demonstrate that extinction events have reduced the overall diversity of crocodilian skull configurations
4. Support the claim that Madagascar species represent the ancestral form from which modern saltwater crocodiles descended
5. Establish that genetic analysis is insufficient for understanding evolutionary relationships among crocodilian species

GRE RC Practice | Moderate | ~140 words

Crocodilian evolutionary history demonstrates exceptional survival across multiple mass extinction events that eliminated most contemporary species. During the Triassic period, early crocodilian relatives occupied diverse ecological roles, with some developing herbivorous habits while others evolved bipedal locomotion similar to early dinosaurs. The Triassic-Jurassic extinction event eliminated most of these early forms, forcing surviving lineages to retreat primarily to aquatic environments as dinosaurs dominated terrestrial habitats.

Throughout the Mesozoic era, crocodilians underwent significant diversification, producing marine predators like Dakosaurus with shark-like adaptations and massive terrestrial forms such as Deinosuchus that exceeded twelve meters in length. After the asteroid impact that ended the dinosaur age, crocodilian survivors rapidly diversified into modern ecological configurations. Contemporary crocodilian species represent the culmination of this extended evolutionary trajectory, having successfully navigated multiple extinction crises through adaptive flexibility rather than remaining unchanged relics of the past.

Question Type: Main Idea | Question Difficulty: Medium

The main idea of the passage is that:

1. Crocodilians survived the asteroid impact that eliminated dinosaurs while other reptile groups perished
2. Crocodilian evolutionary success contrasts sharply with the extinction patterns observed in dinosaur lineages
3. Crocodilians achieved their current ecological dominance through opportunistic expansion during extinction events
4. Crocodilians represent a lineage characterized by adaptive resilience across multiple geological periods
5. Morphological adaptations enabled crocodilians to transition successfully from terrestrial to aquatic environments