[Campbell Biology P.698] According to the passage, what is the primary hypothesized reason w... | Practice Question

According to the passage, what is the primary hypothesized reason why bilateral flower symmetry is associated with increased rates of speciation in plants?

  • A: Bilateral flowers attract a wider range of generalist pollinators, increasing genetic diversity.
  • B: The unique landing position required for nectar collection in bilateral flowers leads to highly specific pollen transfer.
  • C: Bilateral flowers produce more pollen grains than radially symmetrical flowers, enhancing fertilization success.
  • D: Radial flowers are evolutionarily older and thus have slower speciation rates compared to bilateral flowers.

Explanation

The passage explains that in bilaterally symmetrical flowers, an insect pollinator can obtain nectar only when landing in a certain position. This constraint ensures that pollen is placed on a specific part of the insect's body, which then contacts the stigma of another flower of the same species. This 'specificity of pollen transfer reduces gene flow between diverging populations and could lead to increased rates of speciation.'