In vascular plants, leaf veins are crucial for such functions as hydraulic conductance and structural reinforcement. Emerging approximately 340 million years ago (MYA) during the Carboniferous Period, the first vascular plants had relatively simple branched vein structures, but beginning around 320 MYA, reticulate (netlike) venation evolved multiple times in different lineages despite greater associated energy costs. Since reticulation is linked to increased robustness against ecological stressors, one hypothesis posits that the relatively dry interglacial climate of the Carboniferous may explain this trait’s evolution.
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Verbal·Craft and Structure·Text Structure and Purpose
mediumWhich choice best states the main purpose of the text?
A
To outline a scientific debate about the timing of various adaptations found in vascular-plant lineages and evaluate the merits of these competing interpretations.
B
To compare the different functions served by two types of venation patterns found in Carboniferous vascular plants and explain why vascular plants are now more common than nonvascular plants are.
C
To provide an overview of the evolutionary history of a particular adaptation found in some leaf venation structures and identify a potential driver of this adaptation.
D
To introduce a hypothesis about the emergence of leaf vasculature in Carboniferous plants and summarize experimental evidence that substantiates the hypothesis.