Multiple Choice
Which type of natural selection removes individuals with average traits, favoring those at both extremes of the phenotypic range?
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1. Introduction to Biology
Natural Selection and Evolution
Multiple Choice
Which of the following is part of a clade believed to have died out, leaving no descendants?
A
Birds
B
Crocodilians
C
Trilobites
D
Mammals
Verified step by step guidance1
Understand the concept of a clade: A clade is a group of organisms that includes a common ancestor and all its descendants. Some clades have living descendants, while others have gone extinct without leaving any living members.
Analyze the options provided: Birds, crocodilians, and mammals are all part of clades that have living descendants today. For example, birds are part of the clade Aves, crocodilians belong to the clade Archosauria, and mammals are part of the clade Mammalia.
Identify the extinct clade: Trilobites are an extinct group of marine arthropods that were highly diverse during the Paleozoic era. They belong to a clade that left no living descendants, as they completely died out during the Permian-Triassic extinction event.
Compare the options: Since trilobites are the only group listed that belong to a clade with no living descendants, they are the correct answer to the question.
Conclude the reasoning: The clade of trilobites is an example of a lineage that has entirely disappeared, unlike the other options, which represent clades with extant members.
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