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Multiple Choice
Which of the following groups of species is a monophyletic group (clade)?
A
All flying animals (bats, birds, and insects)
B
All species of birds (Class Aves)
C
All warm-blooded animals (birds and mammals)
D
All aquatic mammals (whales, dolphins, and seals)
Verified step by step guidance
1
Understand the definition of a monophyletic group (clade): A monophyletic group includes an ancestor and all of its descendants. This means that all members of the group share a common ancestor, and no species outside the group are descended from that ancestor.
Analyze the first option: 'All flying animals (bats, birds, and insects)'. These species do not form a monophyletic group because bats are mammals, birds belong to Class Aves, and insects are arthropods. They do not share a single common ancestor that includes only these species.
Analyze the second option: 'All species of birds (Class Aves)'. Birds are a monophyletic group because they all share a common ancestor and include all descendants of that ancestor. This fits the definition of a clade.
Analyze the third option: 'All warm-blooded animals (birds and mammals)'. Warm-bloodedness (endothermy) is a trait that evolved independently in birds and mammals, so they do not share a single common ancestor that includes only these species. Therefore, this is not a monophyletic group.
Analyze the fourth option: 'All aquatic mammals (whales, dolphins, and seals)'. These species do not form a monophyletic group because seals are more closely related to terrestrial carnivores (like dogs and bears) than to whales and dolphins, which are cetaceans. Thus, they do not share a single common ancestor that includes only these species.