Explain why adaptive benefits depend on the environment
A feature can help in one setting and involve costs in another.
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Recall inherited features, phenotype, diffusion, photosynthesis and transpiration. Diagrams are original schematics; comparison records are invented and use only the stated assumptions.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Why include the environment in an adaptive-feature explanation?
What you will learn
- Link a feature to its environmental context
- Interpret benefits without claiming universal superiority
Original schematic and invented comparison records. Features, environment, inheritance information and measurement limits are stated separately.
| Feature or record | Interpretation |
|---|---|
| Starting groups | 20 birds per feature per environment |
| Cold offspring | Dense 40 / less-dense 28 |
| Warm offspring | Dense 24 / less-dense 32 |
| Means | Cold 2.0 / 1.4; warm 1.2 / 1.6 |
Link a feature to its environmental context
Adaptive benefits depend on conditions. In the stated cold-habitat case, insulation reduces heat loss when the body is warmer than its surroundings. In a warmer setting where heat must be lost, the same insulation can make heat transfer away from the body more difficult. That does not make the inherited feature universally bad or good. Explain the direction of heat transfer and the actual environmental problem instead of ranking organisms as generally superior.
The invented comparison records use equal starting groups of twenty birds per feature per environment. Dense-feather birds produce forty surviving offspring in the cold setting and twenty-four in the warm setting. Less-dense birds produce twenty-eight and thirty-two respectively. Divide offspring by the original twenty birds to compare output per starting bird: 2.0 versus 1.4 in cold conditions, and 1.2 versus 1.6 in warm conditions.
Interpret benefits without claiming universal superiority
These are group totals, not a claim that each individual had a fractional number of offspring. An average of 1.4 offspring per starting bird can result from different whole-number individual outcomes. The records also do not guarantee future outcomes. Age, food, disease, other inherited differences and observation period could affect output unless the case controls them. The dataset illustrates a context-dependent association, not proof from counts alone that feather density caused every difference.
A stronger explanation combines supplied inheritance information, a plausible mechanism and suitable evidence. State which environment favours the feature in this record and avoid moving beyond the record’s scope. Competition and the transmission of alleles over generations belong to the later Selection sequence. Here, the important habit is to give a conditional explanation: a feature may help survival and reproduction under specified conditions while involving a trade-off elsewhere.
Sources for this lesson
Pause and explain
What is 28 surviving offspring from 20 starting birds?
Worked example
Compare the two feather groups’ offspring output per starting bird in each environment.
Show the worked solution
- Divide the cold totals 40 and 28 by their equal starting groups of 20.
- Divide the warm totals 24 and 32 by 20 and compare the order within each environment.
Answer Cold: dense 2.0 and less-dense 1.4 offspring per starting bird. Warm: dense 1.2 and less-dense 1.6. The ranking changes with context; the totals alone do not prove causation.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Find the dense-minus-less-dense difference in offspring per starting bird in the cold record.
Give me a hint
Normalize both totals by twenty first.
Compare my reasoning
- 40/20 = 2.0 and 28/20 = 1.4.
- Subtract 1.4 from 2.0.
The difference is 0.6 offspring per starting bird in this invented cold record.
Look for these in your work
- Equal denominators used
- Difference and context stated
Use the warm totals 24 and 32 to calculate and compare output per starting bird.
Give me a hint
Each group starts with twenty birds.
Compare my reasoning
- 24/20 = 1.2 and 32/20 = 1.6.
- The less-dense group has the larger average by 0.4.
Warm record: dense 1.2 and less-dense 1.6; the less-dense group’s average is higher by 0.4 offspring per starting bird.
Look for these in your work
- Both means correct
- Warm-context comparison
A report says dense feathers cause better reproduction in every habitat because the cold total is higher. Evaluate the claim.
Give me a hint
Check the warm record and the experimental information.
Compare my reasoning
- The warm record has the opposite ordering.
- The records alone do not exclude age, food or other group differences.
The universal claim is contradicted by the warm comparison. A causal claim also needs an appropriate design and controls, beyond these invented totals.
Look for these in your work
- Context reversal identified
- Causal evidence limit
Common mistakes
- Ranking a feature without its environment
- Reading a group average as each bird’s exact output
- Treating invented association as a controlled causal result
What can you explain now?
What is 28 surviving offspring from 20 starting birds?
Compare with the explanation
1.4 offspring per starting bird
28 divided by 20 gives a group average of 1.4.
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Make it stick
Without your notes, link a feature to its environmental context and interpret benefits without claiming universal superiority. Explain the mechanism and keep the stated environment and evidence limits clear.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.