Recognise fish and amphibian features
Compare adult body covering and gas exchange using the reported life stage.
Section 1.3 · Features of organisms
Exam scope and assessment notes
Core and Extended · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Read the stated observations before choosing a group.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What do the five vertebrate groups share?
What you will learn
- Identify fish from fins, gills and typical scales.
- Distinguish adult amphibians and their life-cycle stages.
Vertebrates share a backbone
Fish, amphibians, reptiles, birds and mammals are vertebrate groups. The shared backbone separates them from arthropods. Fish typically have fins, a scaled body covering and gills for gas exchange in water. Use a combination of the reported features, since a single unusual species may differ from a simple group summary.
Amphibians usually have moist skin without scales. Common examples develop from aquatic larvae using gills to adults with lungs and skin contributing to gas exchange. The adult and larval stages therefore need not have identical features.
Record stage rather than guessing from habitat
An adult frog with moist scaleless skin is consistent with an amphibian. A tadpole with gills should be interpreted using its life-cycle context rather than automatically being classified as a fish. Neither living in water nor laying eggs alone separates all the vertebrate groups.
These summaries give the main syllabus features, not a claim that every member has the same reproductive method. When a question supplies diagnostic observations, prioritise those observations and the stated developmental stage.
Pause and explain
Which observation supports an adult amphibian?
Worked example
A vertebrate has fins, gills and scales and is described as an adult. Which group is supported?
Show the worked solution
- Confirm the backbone places it among vertebrates.
- Use the combination of fins, gills and scales.
- That combination supports fish.
Answer Fish.
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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.
An adult specimen has a backbone, fins, scales and gills. Name the supported group and two features.
Give me a hint
Use the full observed set.
Compare my reasoning
- The backbone confirms a vertebrate.
- Fins and gills support fish.
- Scales provide another typical feature.
Fish; fins and gills, with typical scales.
Look for these in your work
- Correct group.
- Two diagnostic features.
A frog develops from a gill-bearing tadpole into an adult with moist scaleless skin. Explain the classification.
Give me a hint
Keep the stages of one life cycle connected.
Compare my reasoning
- Gills describe the larval stage.
- The adult features fit amphibians.
- The change does not make the stages separate vertebrate groups.
Amphibian, with stage-dependent gas exchange features.
Look for these in your work
- Use the adult skin evidence.
- Explain the stage difference.
A photograph shows a vertebrate in water but no clear covering or gas-exchange structures. What should you inspect next?
Give me a hint
Seek features that separate the groups.
Compare my reasoning
- Habitat gives limited information.
- Look for scales or moist skin, fins and gas-exchange structures.
- Combine the observations with life stage.
Inspect body covering, fins or limbs, gas-exchange structures and life stage.
Look for these in your work
- Avoid a habitat-only answer.
- Name useful structural observations.
Common mistakes
- Water habitat alone is insufficient.
- A larva may differ from its adult group features.
What can you explain now?
Why should a tadpole with gills not automatically be called a fish?
Compare with the explanation
It is a larval amphibian in the stated life cycle.
Classification uses life-cycle context and other features, not gills alone.
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Make it stick
Compare an adult fish with an adult amphibian and explain why life stage matters.
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.