A2. FOSSIL FERN
Ferns are familiar, but relatively primitive plants that lack flowers and true seeds. They are among the earliest land plants to appear in the fossil record. Early in their history, ferns were the dominant plants in land-based communities. Many developed thick trunks and grew to great heights. They were the trees of their time. Today, however, ferns are relatively small, bushy plants, commonly found in the understory of temperate and sub-tropical forests. More advanced, flowering plants have replaced them as the dominant plant constituents of most modern terrestrial ecosystems. You have two specimens: a modern fern (Osmunda regalis ); and a fossil fern (Neuropteris hirsutus). Neuropteris is Pennsylvanian in age (315 ma (mille annum, i.e. million years)).
|Modern fern (Osmunda regalis).||Fossil fern (Neuropteris hirsutus).|
Parts of a fern
A2.1 In Osmunda do pinnae on opposite sides of the main axis branch off the axis in pairs or alternately?
A2.2 In Neuropteris do pinnae on opposite sides of the main axis branch off the axis in pairs or alternately?
A2.3 What does your observation imply about the magnitude of evolutionary change in ferns (think: what will the evolutionary advantage of pinnae branching off alternately and loosing one leaf against branching off a single nod and loosing two leaves at the same time)?
©J.A. Chamberlain, Jr. - Brooklyn College - Earth and Environmental Sciences