Interpret a bird-foot schematic using supplied habitat evidence
Describe the visible membrane, then use the stated information to explain its role.
Section B17.2 · Selection
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
What feature is visible in the original schematic?
What you will learn
- Describe a feature from a labelled image
- Build a supported mechanism from image and information
Original schematic and invented comparison records. Features, environment, inheritance information and measurement limits are stated separately.
| Feature or record | Interpretation |
|---|---|
| View | Original top-view foot schematic |
| Visible feature | Membrane between three forward toes |
| Supplied motion | Backward water push supports forward propulsion |
| Not shown | Allele, speed or universal advantage |
Describe a feature from a labelled image
When interpreting an image, start with a description that another reader can check. The original top-view foot schematic shows three forward toes connected by a membrane. Calling it a large foot is less precise than identifying the membrane between the toes. This is a schematic of a swimming-bird case, not a photograph, anatomical scale measurement or identification key for a named species. The labels indicate the structures that the explanation must use.
The case information states that spreading the connected toes increases the area pushing against water during the backward stroke. The water is pushed backwards and the resulting force helps propel the bird forwards. The habitat is a pond where movement helps the birds reach food and breeding sites. Connect the image’s membrane with the supplied movement mechanism and those contextual benefits instead of saying that webbing is useful because the bird swims.
Build a supported mechanism from image and information
Not every consequence can be seen. The drawing does not reveal an allele, show breeding records, measure swimming speed or demonstrate that webbing is best for every activity. The case stipulates that this feature is inherited; that claim comes from information, not toe shape. Walking on land and movement through water can involve different demands, so avoid a universal assertion that a broader membrane improves every form of movement.
For an unfamiliar image, follow the same method: describe, connect, qualify. Identify the visible feature, use the supplied environment or functional observations, and state the limit. If the image changes viewpoint or lacks a scale bar, do not invent dimensions. The written activity practises interpretation and explanation; it does not certify practical skill, the ability to identify every bird species or whole-qualification mastery.
Sources for this lesson
Pause and explain
Which explanation uses both structure and mechanism?
Worked example
Explain the membrane’s adaptive role using the schematic and the supplied pond case.
Show the worked solution
- Describe the membrane joining the three forward toes and the increased area when spread.
- Use the stated backward water push to explain forward propulsion and access to food and breeding sites.
Answer The inherited webbing in this case creates a broader paddle surface, helping propulsion through pond water and access to resources and breeding sites. The drawing alone does not establish inheritance or speed.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
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.
Describe the adaptive feature visible in the labelled top-view foot model.
Give me a hint
Name the connection between the toes.
Compare my reasoning
- Identify the three forward toes.
- Describe the membrane connecting them rather than an unmeasured size.
A membrane joins the three forward toes, making a broader surface when they spread.
Look for these in your work
- Visible structure named
- No invented measurement
Use the supplied backward-stroke information to connect the webbing with pond movement.
Give me a hint
Trace structure to water push to propulsion.
Compare my reasoning
- The spread membrane presents a broader surface to water.
- Pushing water backwards helps move the bird forwards toward food and breeding sites.
In the stipulated pond case, the webbed surface helps push water backwards and propel the bird forwards, supporting access to food and breeding sites.
Look for these in your work
- Motion mechanism
- Environmental benefit
A learner identifies the bird’s allele and exact swimming speed from the schematic. Explain why those conclusions fail.
Give me a hint
Check what information an external outline contains.
Compare my reasoning
- The drawing shows structure but no genetic sequence or breeding evidence.
- It includes neither distances and times nor speed measurements.
Neither conclusion follows. Genotype needs genetic or inheritance evidence, and speed needs appropriate movement measurements; the schematic provides neither.
Look for these in your work
- Genetic evidence limit
- Measurement evidence limit
Common mistakes
- Giving only a vague size description
- Reading genotype or speed directly from a drawing
- Giving a benefit with no structural mechanism
What can you explain now?
Which explanation uses both structure and mechanism?
Compare with the explanation
The spread webbed surface pushes more water during the stated stroke
It connects the drawn membrane to the supplied motion context.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Without your notes, describe a feature from a labelled image and build a supported mechanism from image and information. 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.