[Campbell Biology P.755] How did the body segmentation evolve from early ancestors like lobo... | Practice Question

How did the body segmentation evolve from early ancestors like lobopods and trilobites to modern arthropods, according to the text?

  • A: Early arthropods and lobopods had functionally united "body regions" from the start, a feature passed directly to modern arthropods.
  • B: While lobopods and early arthropods (like trilobites) showed little segment variation, later arthropods evolved "body regions" through segments becoming functionally united and specialized.
  • C: The primary evolutionary change was the development of hard exoskeletons, which made segment variation unnecessary in early arthropods.
  • D: Modern arthropods lost their segmented body plan, unlike their segmented lobopod ancestors.

Explanation

The text states: 'Lobopods such as Hallucigenia... had segmented bodies, but most of their body segments were identical to one another. Early arthropods, such as the trilobites, also showed little variation from segment to segment.' It then continues: 'As arthropods continued to evolve, groups of segments tended to become functionally united into "body regions" specialized for tasks such as feeding, walking, or swimming.' This describes the progression from uniform segments to specialized body regions.