Question

which phrase best defines the term homologous structures?
o structures that are so similar that they imply a common ancestor
o structures that have the exact same features and functions
o structures that have the same features
o structures that had a function in an ancestor but dont have that function today

Explanation:

Homologous structures are anatomical features in different organisms that have a similar underlying structure (due to common ancestry), even if their functions differ. Option 1 correctly emphasizes the implication of a common ancestor. Option 2 is incorrect as homologous structures don't necessarily have the exact same functions (e.g., human arm vs. bat wing). Option 3 is too vague as it just mentions "same features" without the key aspect of common ancestry. Option 4 describes vestigial structures, not homologous ones.

Answer:

structures that are so similar that they imply a common ancestor