Conifers Encased Sperm in Pollen Grains, Allowing Them to Flourish in Dry Habitats
In the previous section, the technique of reproduction would involve transferring egg and sperm through water. This technique lasted millions of years.
Carboniferous Period: 360 million to 286 million years ago.
During this period, the climate was warm and moist. It had many stretched of land covered with forests of giant tree ferms and club mosses. They produced swimming sperm.
Permian Period: This was the period between 286 and 245 million years ago. Some plants inhabiting regions that were dry started to evolve reproductive strategies. These strategies did not depend on water (like the other plants). These were conebearing plants.
conifers - conebearing plants mentioned above that had their eggs retained in their parent plant and the sperm encased in drought-resistant pollen grains that the wind blew from plant to plant. It is a member of a class of tracheophtes (Coniferophyta) that repoduces by means of seeds formed inside cones and that retains its leaves throughout the year.
The pollen releases sperm eggs directly into living tissue, eliminating the need for a film of water.
About 250 Million Years Ago: Swamps began to drain. The moist climates became dry. Many plants that used swimming sperm became extinct. The confifers, which didn't depend on water for reproduction, spread. The conifers florished on the dry land.
FOR YOUR INFORMATION:Today forests of conifer trees are called pinetums. To the right is a drawing of a group of conifer trees from .