Final answer:
A second-year pine cone is the mature stage of a pine cone in its second year of growth when the cone scales have opened up to release the seeds for dispersal.
Step-by-step explanation:
A second-year pine cone refers to the stage of development that a pine cone reaches in its second year of growth. In the first year, pine cones are known as seed cones and are small and green. In the second year, the cone matures and becomes larger and brown in color. The scales of the cone open up, releasing the seeds for dispersal. The structure of a second-year pine cone varies depending on the species of pine, but generally, it consists of cone scales that protect the seeds.