Evidence of Evolution
Evolution is not one observation but a convergence of independent evidence, and Topic 7.6 is where you learn to read the lines that all point to the same conclusion: common ancestry. The fossil record lays out change through time — transitional forms and the ordered appearance of groups in rock layers. Comparative anatomy adds homologous structures, like the shared bone plan of a human arm, a whale flipper, and a bat wing, which make sense only if these species inherited one ground plan from a common ancestor. Molecular biology pushes deeper: shared DNA, RNA, and protein sequences — even a nearly universal genetic code — track relatedness, so the more sequence two species share, the more recently they diverged. And biogeography shows how the geographic distribution of species mirrors their evolutionary history and the movement of landmasses.
The sharpest distinction to hold onto is homologous versus analogous. Homologous structures share a common ancestor and underlying anatomy even when they do different jobs; analogous structures — a bird wing and an insect wing — do the same job but evolved independently and signal convergent evolution, not close kinship. Confuse the two and you will read similarity as relatedness when it is really similar selective pressure. Keep function separate from ancestry.
Interactive · Evidence of Evolution
Move across the four lines of evidence — fossils, anatomy, molecules, and biogeography — and see how each independently points to common ancestry. Sort structures as homologous or analogous, and watch how shared ancestry and convergent evolution produce similarity for entirely different reasons.
Evidence of Evolution · Open the full sandbox →The mistakes here cluster around a few failure modes. Students imagine evolution is just a guess or an unproven hunch because it is "only a theory" — but in science a theory is a well-supported, testable explanation backed by convergent evidence, not a casual guess (U7-BIO13). They treat any similarity as proof of close relatedness, mistaking analogous structures produced by convergent evolution for homologous ones (U7-BIO12). And they assume a single line of evidence stands alone, when the strength of the case comes from fossils, anatomy, molecular data, and biogeography independently converging on the same tree (U7-BIO13). Every scenario in this topic asks you to weigh the evidence for common ancestry and to keep ancestry separate from mere resemblance.
The work
3 ways in · any order
Lesson
Evidence of Evolution
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Four independent lines of evidence — the fossil record, homologous anatomy, shared molecular and genetic sequences, and biogeography — converge on common ancestry. The lesson walks the ways students misread that: taking "theory" to mean a guess, mistaking analogous structures for homologous ones, and treating a single line of evidence as the whole case. It closes with a ten-scenario applet that asks you to weigh the evidence and keep ancestry separate from resemblance.
Diagnostic
10-item topic check
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Ten items on the evidence for evolution — that a scientific "theory" is a well-supported explanation, not a guess (U7-BIO13); that analogous structures from convergent evolution are not proof of close relatedness the way homologous structures are (U7-BIO12); and that the case rests on fossils, anatomy, molecular data, and biogeography independently converging, not on any one line alone (U7-BIO13). Take it cold to surface which of these are still tangled, or after the lesson to confirm they hold.
Targeted Practice
Drill a single misconception
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Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears the misconception and moves you to the next.