S1 Science: Classification And Dichotomous Keys (Paper 1 (basics))

S1 Science: Classification and Dichotomous Keys (Paper 1 (basics))

2026-11-14

← Back to the Secondary Science chapter index

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 1 (basics))

This paper covers the basic unit of classification, the seven ranks, the form of a scientific name and the basic use of a dichotomous key.

Direct answers　The species is the basic unit, features increase going down the ranks, and each key step splits on one observable 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)

FoundationWhat is the basic unit of biological classification?
FoundationWhat are the seven main ranks of classification, from largest to smallest?
FoundationWhat two parts make up a scientific name?
IntermediateHow many choices does each step of a dichotomous key offer?
IntermediateA dichotomous key has 4 steps. At most how many kinds can it separate?
IntermediateInto which five groups are vertebrates divided?
ChallengeWhich pair is more closely related: two species in one genus, or two species in one family but different genera?
ChallengeSix kinds must all be separated by a dichotomous key. What is the minimum number of steps?
ChallengeA bat has wings and flies, so why is it a mammal rather than a bird?
Error redoA student says every member of one family must belong to the same genus. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	The species	Members of one species can interbreed naturally and produce fertile offspring.
2	Kingdom, phylum, class, order, family, genus and species, seven ranks in all	From kingdom down to species the shared features increase while the members decrease.
3	A genus name followed by a specific epithet, in Latin and printed in italics	The genus name begins with a capital and the specific epithet is all lower case.
4	Two	Each step splits the specimens into two groups by one observable feature, hence dichotomous.
5	16 kinds	Each extra step doubles the number of endpoints, and 2 to the power 4 is 16.
6	Fish, amphibians, reptiles, birds and mammals	Classification uses body structure and reproduction rather than where the animal lives.
7	The pair in the same genus	Genus is one rank below family, and a lower rank means more shared features and closer kinship.
8	3 steps	n steps give at most 2 to the power n endpoints, so 8 endpoints are needed for 6 kinds.
9	It has fur, gives birth to live young and feeds them milk	Classification follows body structure and reproduction rather than the ability to fly.
10	A family is larger than a genus, so one family may contain several genera	A higher rank contains more organisms, so sharing a family does not mean sharing a genus.

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.