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CAIE IGCSE Biology 1.2 Concept and Uses of Classification Systems Questions

Practise defining species, using binomial names and keys, and interpreting molecular evidence for evolutionary relationships.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • Classify organisms by shared morphological, anatomical, phenotypic or biochemical features.
  • Define a species by interbreeding to produce fertile offspring, and use genus/species rules in binomial names.
  • Follow paired contrasting statements in dichotomous keys to identify an organism from observable features.
  • Compare DNA or amino-acid sequences and branching points to infer shared ancestry and closer or more distant relationships.

Covered syllabus points

1.2.1—Organisms can be classified into1.2.2—Species as a group of organisms that1.2.3—Binomial species names1.2.4—Dichotomous keys based on identifiable1.2.5—Classification systems aim to reflect1.2.6—DNA base sequences for classification1.2.7—Groups of organisms which share a more

Question 1

[Maximum number: 1]

Viruses can cause diseases.

Fig. 6.1 shows four different viruses.

Fig. 6.1

Fig. 6.1

Suggest one feature that could be used to classify viruses into groups.

Question 2

[Maximum number: 2]

Fig. 3.3 shows the parts of two flowers from two different plants of the same species.

Fig. 3.3

Fig. 3.3

Describe what is meant by the term species.

Question 3

[Maximum number: 1]

Fig. 6.1 shows a boreal toad, Anaxyrus boreas. This toad is listed as an endangered species.

Fig. 6.1

Fig. 6.1

State the genus of the boreal toad.

Question 4

[Maximum number: 2]

Fig. 1.1 shows four arthropods.

Fig. 1.1

Fig. 1.1

Fig. 1.2 is a dichotomous key for the arthropods shown in Fig. 1.1.

Complete Fig. 1.2 by writing suitable statements in:
- box 2 to identify species B
- box 3 to separate species C and A.

Fig. 1.2

Fig. 1.2

Question 5

[Maximum number: 1]

Two animals have an identical sequence of amino acids in one of the proteins found in their cells.

What does this indicate about these animals?

A

They have been eating the same types of food.

B

They have not been exposed to substances that cause mutation.

C

They must be members of the same genus.

D

They share an ancestor.

Question 6

[Maximum number: 1]

What is used as a means of classification?

A

the number of strands of mRNA

B

the shape of DNA molecules

C

the sequence of bases in DNA

D

the types of bases in DNA

Question 7

[Maximum number: 4]

A DNA molecule has two strands as shown in Fig. 6.1.

Fig. 6.1

Fig. 6.1

Question (a)

(a)

The most closely related species have the fewest differences between their DNA sequences.

State which two plant species shown in Table 6.1 are most distantly related to each other.

[ 1 ]

Question (b)

(b)

The most closely related species have the shortest distance from a branching point on a classification tree.

Use the information in Table 6.1 to complete the classification tree in Fig. 6.3. Write the letter corresponding to species B, C, D and G in the box next to the correct branch of the classification tree.

Fig. 6.3

Fig. 6.3

[ 3 ]
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