EXERCISE 4 EVOLUTION OF THE OVULE: GYMNOSPERMS

Seed

It is the synapomorphy for the spermatophytes (gymnosperms and angiosperms) which separates them from the rest of vascular plants.

embryo; nutritive tissue; seed coat

The seed comprises an ___________ surrounded by ______________ and enveloped by a _____________.

gymnosperms; carpel

The ____________ are segregated from the angiosperms by having ovules/seeds not enclosed by a _________.

megasporophylls

The ovules/seeds are instead borne on surface of a leaf-like structure or ___________________ which could be variously modified scales, bracts or fleshy receptacle.

haustorial pollen tube; anemophilous; endosperm; vessels; resin canals; truss; unisexual

Other unifying characters include ___________, mostly _____________ pollination, utilization of primary _________, typical absence of ___________ in secondary wood, presence of ___________, and the reproductive organs borne on ‘_________’ (modified axis) that are typically reduced to pollen sacs and ovules arranged in a _________ strobili — although exceptions can be found

unisexual

Notably, when ‘flower’ is interpreted as a short shoot with specialized leaves (Glover, 2007), logic implies that gymnosperm cones could also be described as a flower, though the organization of the cone is ________ (Ronse De Craene, 2010).

monophyletic; paraphyletic

Analyses of morphological and molecular data showed that extant gymnosperm taxa are clearly ____________, but are considered ______________ when synthesized with numerous and diverse groups of related fossils (e.g. pteridosperms, Bennetittales, etc.)

living fossils

Likewise, paleobotanic records show that gymnosperms have relatively well-conserved morphological features exemplified by the numerous species considered ________________ (e.g. Ginkgo, Wollemia, Welwitschia).

At the end of this module, you should be able to:

1. identify and classify representative species gymnosperms by examining the different morpho-anatomical structures;

2. visually illustrate the relationships of gymnosperms, and

3. know their ecological significance and economic importance

At the end of this module, you should be able to:

1. ________________________________________

2. ________________________________________

3. ________________________________________