[Campbell Biology P.685] The flowchart illustrates the initial steps of the pine life cycle ... | Practice Question

The flowchart illustrates the initial steps of the pine life cycle on land. Considering the overall adaptations discussed for seed plants, what is the most significant evolutionary advantage provided by a pollen grain being released from a cone and then forming a pollen tube upon reaching an ovule?

  • A: It ensures that the male gametes are directly exposed to the external environment, facilitating rapid fertilization.
  • B: It eliminates the need for liquid water for sperm transport, allowing seed plants to reproduce in diverse terrestrial environments.
  • C: It primarily serves to nourish the developing embryo before the seed is formed.
  • D: It enhances genetic diversity by promoting cross-pollination exclusively through animal vectors.

Explanation

The ability of pollen to be transported by wind or animals, and then to form a pollen tube upon reaching the ovule, represents a crucial adaptation that freed seed plants from the need for liquid water for fertilization. This allowed them to colonize a vast array of terrestrial habitats, which was a major step in their evolutionary success.