Question

Write two or more paragraphs comparing and contrasting the different gymnosperm phyla from each other. Don’t just list the characteristics! You may use slide or live specimens, but make sure to focus on characteristics that will help you in identifying each division/class. What would be some evolutionary advantages that gymnosperms have compared to seedless vascular plants? Why would these be advantages?

Answer 1

COMPARISON OF THE $ PHYLA OF GYMNOSPERMS

Coniferophytes - They are typically tall trees that usually bear scale-like or needle-like leaves. Water evaporation from leaves is reduced by their thin shape and the thick cuticle. Snow slides easily off needle-shaped leaves, keeping the load light and decreasing breaking of branches. A few species are deciduous, losing their leaves in fall. They contain tracheids, but no vessel elements thats why they are soft.

Cycads - Cycads thrive in mild climates. They are often mistaken for palms because of the shape of their large, compound leaves. Cycads bear large cones and may be pollinated by beetles rather than wind, which is unusual for a gymnosperm.

Gingkophytes - Its fan-shaped leaves, unique among seed plants because they feature a dichotomous venation pattern, turn yellow in autumn and fall from the tree. It is planted in public spaces because it is unusually resistant to pollution. Male and female organs are produced on separate plants.

Gnetophytes - They have broad leaves. In tropical and subtropical zones, gnetophytes are vines or small shrubs. All gnetophytes possess vessel elements in their xylem.

(a) Ephedra (b) Gnetum (c) Welwitschia

ADVANTAGES OF GYMNOSPERMS

Gymnosperms were the first seed plants. They do not make flowers or fruits though, so their seeds are unprotected. Wind-dispersed pollen doesn't need water for fertilization. The seed protects the embryo from drying out. The seed gives nutrients to the embryo, which helps early plant growth. Since sperm no longer need water to fertilize the egg, plants with pollen can reproduce at more times during the year and in drier habitats. Using seeds for protection and nutrition means that seed plants can get to a lot more places, since they won't dry out in a day.

THE seedless vascular plants needed moist medium for their gametes to fertilize. They also dried out fast if medium becomes dry and hence get wasted.  Their zygote would remain unprotected. These plants were seasonal breeders.