In the late nineteenth century, paleontologists first observed that some dinosaur fossils preserved impressions of structures resembling modern bird feathers. To determine whether these structures were indeed feathers, researchers analyzed the chemical composition of the fossilized filaments. They discovered that the filaments contained keratin, a protein found in the feathers of living birds. This biochemical evidence led the researchers to conclude that these ancient reptiles possessed proto-feathers. Therefore, they hypothesized that feathers evolved initially for insulation rather than flight, a view that is now widely accepted in the scientific community.
Which choice best describes the overall structure of the text?
- It introduces a scientific observation, describes an investigation into that observation, and explains the conclusion reached by researchers.Answer
- BIt compares two competing theories about dinosaur feathers and evaluates the evidence supporting each theory.
- CIt describes a specific study of dinosaur fossils in order to argue that flight was the primary function of early feathers.
- DIt outlines a historical debate about dinosaur classification and details the steps taken to resolve that debate.
Answer
It introduces a scientific observation, describes an investigation into that observation, and explains the conclusion reached by researchers.
The correct option describes the rhetorical flow of the text: it starts with the discovery of feather-like structures in fossils (an observation), describes the chemical analysis performed on them (an investigation), and explains that the feathers were concluded to have evolved for insulation (a conclusion).
Step-by-Step Solution
Key Concept
Overall Text Structure Analysis