Question

what observation led researchers to propose that chloroplasts evolved from cyanobacteria?
both produce proteins.
both contain mitochondria.
both provide structure to cells.
both perform photosynthesis.

Explanation:

To determine the correct answer, we analyze each option:

• "Both produce proteins": Many organisms produce proteins, so this is not a unique characteristic linking chloroplasts and cyanobacteria.
• "Both contain mitochondria": Cyanobacteria are prokaryotes and do not have mitochondria, so this is incorrect.
• "Both provide structure to cells": Providing structure is not a key feature related to the evolution of chloroplasts from cyanobacteria.
• "Both perform photosynthesis": Cyanobacteria are photosynthetic prokaryotes, and chloroplasts are the organelles in eukaryotic cells that perform photosynthesis. This shared ability to do photosynthesis is a key observation supporting the endosymbiotic theory (that chloroplasts evolved from cyanobacteria - like organisms).

Answer:

D. Both perform photosynthesis.