- A Organs that perform critically important and largely indispensable physiological functions important for daily survival under usual circumstances
- B Reduced, non-functional remnants of organs that were functional in ancestors: human appendix, coccyx (tailbone), ear muscles, body hair, wisdom teeth
- C Organs that develop and gradually mature mainly after birth, throughout the early years of childhood growth according to most researchers in the majority of cases studied
- D Newly evolved organs that have appeared fairly recently and spread within the human evolutionary lineage as widely reported in standard practice
Correct answer: B. Reduced, non-functional remnants of organs that were functional in ancestors: human appendix, coccyx (tailbone), ear muscles, body hair, wisdom teeth
Explanation: Vestigial organs are evolutionary remnants of structures that had functions in ancestral species but are now reduced or non-functional. Human examples: coccyx (remnant of tail), appendix (reduced cecum for cellulose digestion), ear muscles (cannot move ears), plica semilunaris (third eyelid remnant), body hair (piloerection).
Concept context
Origin of life, Darwin's theory, natural selection, speciation, and evidence for evolution.