Distinguish crustaceans and myriapods
Use antenna-pair number and body segmentation while allowing variation in leg count.
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
Which antenna pattern is typical of crustaceans?
What you will learn
- Identify crustacean and myriapod patterns.
- Explain why five leg pairs is not a universal crustacean rule.
Antennae and segments are useful evidence
Crustaceans typically have two pairs of antennae and jointed appendages; many familiar examples live in water and have a body divided into cephalothorax and abdomen. Leg number varies across the group. A crab or lobster often has five walking-leg pairs, but that is not an exception-free rule for every crustacean.
Myriapods have a head followed by many similar body segments with many legs and one pair of antennae. Centipedes usually have one leg pair per leg-bearing segment; millipedes typically have two pairs on many of their apparent body segments.
Avoid literal interpretations of common names
Centipede does not require exactly one hundred legs, nor millipede exactly one thousand. The segment and antenna pattern is more useful than taking the common name as a count. Both groups have the shared arthropod external skeleton and jointed legs.
A woodlouse is a terrestrial crustacean, so living on land does not rule out crustaceans. Use antennae, body organisation and the stated observations; handle an obscured antenna as incomplete evidence rather than proven absence.
Pause and explain
Which combination supports a myriapod?
Worked example
An arthropod has many similar body segments, many leg pairs and one antenna pair. Which group is supported?
Show the worked solution
- The segmented, many-legged pattern supports myriapods.
- One antenna pair is consistent.
- Do not infer a fixed count from the name.
Answer Myriapod.
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.
A stated adult lobster has ten walking legs and two antenna pairs. Convert the walking-leg count and classify.
Give me a hint
Separate legs from pairs.
Compare my reasoning
- 10 ÷ 2 = 5 pairs.
- Two antenna pairs support crustaceans.
- This count describes the supplied lobster, not every crustacean.
5 walking-leg pairs; crustacean.
Look for these in your work
- Correct pair count.
- Keep the count specimen-specific.
Compare a typical centipede and millipede in their leg distribution.
Give me a hint
Compare leg-bearing segments rather than the names.
Compare my reasoning
- Centipede usually has one pair per leg-bearing segment.
- Millipede has two pairs on many apparent segments.
- Both have many segments and one antenna pair.
One versus two pairs on the stated types of segments; both are myriapods.
Look for these in your work
- State the typical pattern with qualification.
- Name the shared group.
A land-dwelling specimen has two antenna pairs and crustacean body features. A student calls it an insect because it is on land. Correct the reasoning.
Give me a hint
Habitat is weaker than the reported structures.
Compare my reasoning
- Insects typically have one antenna pair.
- Two antenna pairs support crustaceans.
- Terrestrial crustaceans exist.
Crustacean features outweigh habitat; land dwelling does not make it an insect.
Look for these in your work
- Use antenna evidence.
- Reject habitat-only classification.
Common mistakes
- Crustacean leg counts vary.
- Habitat and common-name numbers are insufficient alone.
What can you explain now?
Does living on land rule out a crustacean?
Compare with the explanation
No.
Woodlice are terrestrial crustaceans; diagnostic features matter.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Explain the four arthropod groups using leg pairs, antennae and body divisions.
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.