QCE Biology Paper 2 free practice questions with answers

Question 1 (7 marks) [Biodiversity]

(a) Explain why the platypus has been used as an outgroup.

(a) Answer: It is a related mammal that is not a marsupial, so its characters represent the ancestral state against which derived characters in the marsupials can be identified.

• 1 mark: related but outside the group.
• 1 mark: shows the ancestral characters.

(b) Identify a derived characteristic shared by all four marsupials and name the clade it defines.

(b) Answer: The pouch; it defines the clade of marsupials.

• 1 mark: the pouch.
• 1 mark: marsupial clade.

(c) Use the data to determine which two marsupials are most closely related and justify your answer.

Use shared derived characters and the outgroup to build a cladogram.