Final answer:
Pollen-producing plants early in their evolution extended their range into drier environments, facilitated by the evolution of the pollen tube. This adaptation enabled gymnosperms like pines to thrive in drier climates and reproduce over larger distances, ensuring their survival in varying habitats that lacked constant water presence.
Step-by-step explanation:
Early in their evolution, pollen-producing plants could extend their range and move to drier environments. This significant adaptation was facilitated by the development of the pollen tube, which allowed the sperm of these plants to reach the ovum without the need for water, a development critical in the gymnosperms around 300 million years ago. This evolutionary step included various gymnosperms like the now-extinct cordaites, as well as cycads, ginkgos (maidenhair trees), and conifers. It allowed these plants to colonize areas that did not have the constant presence of water, thus expanding into drier environments.
The adaptation to drier climates is significant as it opened up a wider range of habitats where these plants could thrive. For example, pine trees, which are a type of conifer, were able to spread widely and inhabit areas that experienced drying conditions. Additionally, the ability for pollen to be wind-dispersed allowed these early plants to reproduce over larger distances, aiding in their expansion into various environments. As a result, areas such as the Near East, which experienced drier conditions and where the earliest evidence of plant domestication is found, could have been colonized by these early seed plants.
Understanding the importance of climate change and the ability of plants to adapt to varying conditions is highlighted by modern observations. For example, changes in temperature and precipitation are affecting the phenology of modern plants, leading to earlier flowering times. This shift could potentially cause issues with pollination, particularly for those plants that rely on insects which may not be present at the earlier flowering times.
In summary, the correct option for the question 'Early in their evolution, pollen-producing plants could extend their range and move to _____?' is option 2) drier environments.