S1 Science: Classification And Dichotomous Keys (Paper 4 (error Clinic))

S1 Science: Classification and Dichotomous Keys (Paper 4 (error clinic))

2026-11-14

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Tutor Prep Guide · The order of classification ranks, the five kingdoms, binomial names and step by step identification with a dichotomous key

S1 Science: Classification and Dichotomous Keys (Paper 4 (error clinic))

This paper reworks the commonest wrong answers, including the basic unit, name capitalisation, powers of two, and the grouping of bats and whales.

Direct answers　Error clinic practice should separate a faulty concept, a reversed rank direction and a habitat mistaken for a feature.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S1 Science: Classification and Dichotomous Keys
Level	S1

02　Questions (10 items)

FoundationError: a student answered that the basic unit of classification is the family. What is correct?
FoundationError: a student wrote the name in full capitals, PANTHERA LEO. What is the correct form?
FoundationError: a student said each step of a dichotomous key has three choices. How many are there?
IntermediateError: a student said a four step key separates at most 8 kinds. What is the maximum?
IntermediateError: a student called a bat a bird because it has wings. What is the correct group?
IntermediateError: a student called a whale a fish because it lives in the sea. What is the correct group?
ChallengeError: a student said all members of a family share one genus. What is correct?
ChallengeError: a student said two steps can separate six kinds. What is the minimum number?
ChallengeError: a student said shared features decrease from kingdom down to species. What is the correct direction?
Error redoError: a student used living in water as the first feature of a key. What should be used instead?

03　Answers and one-line notes

#	Answer	One-line note
1	The species	The species is the basic unit, while the family sits several ranks above it.
2	Panthera leo, with the genus capitalised and the epithet in lower case	The form of a scientific name follows an international convention and is not a free choice.
3	Two	Dichotomous means only two routes are offered at each step.
4	16 kinds	Each added step doubles the endpoints, and 2 to the power 4 is 16.
5	Mammals, since bats have fur, give birth to live young and feed them milk	Classification uses body structure and reproduction rather than flight.
6	Mammals, which breathe with lungs and give birth to live young	Habitat is not a classification criterion.
7	A family may contain several genera, since a family is larger than a genus	A higher rank holds more members.
8	3 steps	Two steps give only 4 endpoints, too few for six kinds, while three give 8.
9	Shared features increase while the number of members decreases	The species is the most specific unit, so it carries the most shared features.
10	Observable body structures such as a backbone, fins or body covering	Key features must be stable, mutually exclusive and open to direct checking.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

For classification questions ask three things: is the feature observable, are the two options mutually exclusive, and is the question about rank order or about relatedness.Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.