Interpret speciation evidence
Interpret speciation evidence using supplied evidence and a solved model.
About 25 minutes, plus any extended practice
Supplied materials
- All measurements and observations below are supplied classroom examples. They are not data from actual learners or a claim about a particular real site.
- Paper or a browser document for a labeled drawing, table or explanation.
- Worked problem inputs: Separated populations later reunite and exchange genes readily. Was geographic separation alone proof of distinct species?
- Assessment case 1: A mountain separates two populations, but reproductive exchange has not been tested. What is warranted? Which inference or prediction is best supported?
- Assessment case 2: Which scientific label fits the specifically described step or feature? Supplied case: Mating barrier reduces gene exchange.
- Assessment case 3: Which scientific label fits the specifically described step or feature? Supplied case: Sequences differ more over generations.
- Assessment case 4: Which scientific label fits the specifically described step or feature? Supplied case: Only a map is supplied.
- Assessment case 5: Which scientific label fits the specifically described step or feature? Supplied case: Timing barrier prevents reproductive overlap.
- Assessment case 6: Separated groups later reunite and exchange genes readily. What does this limit? Which inference or prediction is best supported?
Learn the idea
Reproductive isolation can reduce gene exchange between diverging populations. Geographic separation alone does not prove separate species. Species concepts have strengths and limitations, especially for fossils and asexual organisms.
Geographic separation means populations occupy disconnected places. Reproductive isolation means gene exchange is reduced by reproductive barriers. Divergence means populations accumulate differences. Evidence limit means supplied records cannot establish species status.
For the supplied mechanism problem, Separated populations later reunite and exchange genes readily. Was geographic separation alone proof of distinct species? No. Geographic isolation can allow divergence, but continued gene exchange is evidence relevant to reproductive isolation. Species status needs an appropriate concept and more evidence.
- Read the supplied problem and mark the structures, processes or quantities named: Separated populations later reunite and exchange genes readily. Was geographic separation alone proof of distinct species?
- Draw the relevant boundary, pathway or comparison and label it using the scientific ideas above.
- Write a causal explanation or calculation, showing how each observation supports the result.
- Compare your reasoning with the worked solution; name a condition that would change or limit the inference.
See the method in action
Worked supplied problem: Separated populations later reunite and exchange genes readily. Was geographic separation alone proof of distinct species? Solution: No. Geographic isolation can allow divergence, but continued gene exchange is evidence relevant to reproductive isolation. Species status needs an appropriate concept and more evidence. This conclusion uses the stated observations and the mechanism explained above; it does not establish every unmeasured feature of a real organism, device or place.
Check your reasoning
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Helpful tips
- Use the feature “populations occupy disconnected places” to justify geographic separation; do not sort by the name alone.
- Distinguish reproductive isolation (gene exchange is reduced by reproductive barriers) from a different process occurring in the same situation.
See the answer and explanation
Geographic separation can permit divergence but alone does not prove distinct species.
Isolation is a condition, while species inference requires appropriate additional evidence.
Take it further
New case: two populations share territory but mate at nonoverlapping times in the supplied model. Expected: a temporal reproductive barrier can reduce gene exchange even without geographic separation.
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More practice: try new cases
Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.
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Check the subject sources
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