This qualitative study analyzed grade 12 biology students' answers to written extended-response questions that describe hypothetical scenarios of animals' evolution. We investigated whether these type of questions are suitable for students (n = 24) to express a meaningful understanding of evolutionary theory. Meaningful understanding is comprised of factual, procedural (rules, algorithms), schematic ("knowing why"), and strategic knowledge (when, where and how to apply knowledge). Evolutionary theory as a multi-level concept includes concepts on three different levels (descriptive, hypothetical, and theoretical). Students' answers are examined as to whether they reflect the meaningful linking of all concepts through appropriate use of scientific language. Results showed that students (a) predominantly linked descriptive concepts and, although expected, (b) demonstrated only some cross-concept-level links (theoretical-descriptive), (c) exhibited even fewer multi-concept-level links (theoretical-descriptive-hypothetical), and (d) avoided the linking of hypothetical concepts with theoretical ones. All these results showed the lack of explanations and reasoning (absence of schematic and strategic knowledge) and knowledge of how to link concepts about evolutionary theory meaningfully. The results indicate further that written extended-response questions are only partially suitable for demonstrating meaningful understanding. Implications for teaching of evolutionary theory are discussed. (Contains 7 tables and 3 notes.)