Homologous structures: Similar structures that perform different functions. These are seen in organisms that are closely related.
Give an example of a homologous structure from this activity:
Possible answers: ulna, radius, carpal, metacarpal, phalange, humerus
Vestigial structures: remnant structures that were once important in the organism’s ancestors, but are no longer used in the same way.
Below are vestigial structures found in humans. For each, hypothesize what its function may have been.
Wisdom teeth larger jaw, replace rotten teeth
Appendix Supplies bacteria to gut to digest leaves
Muscles for moving ear used for directional hearing (hear from different directions)
Body hair body covered in lots of hair for warmth
Little toe used for balance Give an example of a vestigial structure from this activity:
Possible answers: appendix, muscles to move ear, body hair, little toe, wisdom teeth
How do homologous and vestigial structures suggest an evolutionary relationship between species?
Homologous structures show that humans, cats, bats, crocodiles, birds, and whales all have similar bones with different functions, so they must have a common ancestor.
Vestigial structures tell us that humans have structures leftover from an ancient ancestor that are no longer used for their original purpose.
Molecular (DNA) Biology
Molecular (DNA) biologist: A scientist that studies the molecular basis of biological activity, particularly DNA sequences and biochemistry.
Below are sequences of letters that stand for portions of the genes that code for α and β hemoglobin (blood) proteins in different primates.
Compare the DNA sequences from the α hemoglobin for the thick-tailed bushed baby and humans. Circle any differences in base pairs from the human sequence and record the total differences in the data table on this page.