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Multiple Choice
Which of the following statements is consistent with the assertion that protists are paraphyletic?
A
Protists include some, but not all, descendants of their most recent common ancestor.
B
All protists share a single, unique common ancestor not shared with any other group.
C
Protists form a monophyletic group that includes all eukaryotes.
D
Protists are defined by a single, shared derived trait (synapomorphy).
Verified step by step guidance
1
Understand the term 'paraphyletic': A paraphyletic group includes some, but not all, descendants of a common ancestor. This contrasts with a monophyletic group, which includes all descendants of a common ancestor.
Analyze the first statement: 'Protists include some, but not all, descendants of their most recent common ancestor.' This aligns with the definition of a paraphyletic group, as it explicitly states that not all descendants are included.
Evaluate the second statement: 'All protists share a single, unique common ancestor not shared with any other group.' This implies a monophyletic group, which contradicts the assertion that protists are paraphyletic.
Examine the third statement: 'Protists form a monophyletic group that includes all eukaryotes.' This is incorrect because protists are not monophyletic; they do not include all descendants of their common ancestor (e.g., plants, animals, and fungi are excluded).
Consider the fourth statement: 'Protists are defined by a single, shared derived trait (synapomorphy).' Protists are highly diverse and lack a single shared derived trait, which further supports their classification as a paraphyletic group.