Final answer:
The past climate was most likely warm, as inferred from the predominance of fossil leaves with smooth edges, the presence of subtropical palm fossils in Wyoming, and geological climate records indicating a generally warm and humid Tertiary Period.
Step-by-step explanation:
The students question relates to the past climate condition, which can often be inferred from paleobotanical studies, such as the examination of fossilized leaves. Since 75% of the fossil leaves have smooth edges and 25% are toothed, it implies that the past climate was most likely warm. Smooth-edged leaves are typically associated with warmer climates, while toothed leaves often relate to cooler climates. Therefore, a high percentage of smooth-edged leaves suggests that the climate during the time the plant existed was likely warm and less variable.
The presence of fossils such as the palm trees from the Green River Formation in Wyoming indicates a subtropical climate similar to what Florida is like today. During the Tertiary Period, Earth's climate was generally warm and humid, which allowed the diversification of flowering plants and the evolution of mammals. Geological climate records, such as oxygen isotope records, commonly support this understanding of past warm climates.