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- Analyses with outgroups screened to avoid long branches consistently identify all gymnosperms as a monophyletic sister group to angiosperms.
www.pnas.org/doi/full/10.1073/pnas.97.8.4092Phylogeny of seed plants based on all three genomic ... - PNAS
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By far the largest group of living gymnosperms are the conifers (pines, cypresses, and relatives), followed by cycads, gnetophytes (Gnetum, Ephedra and Welwitschia), and Ginkgo biloba (a single living species). About 65% of gymnosperms are dioecious, [5] but conifers are almost all monoecious. [6]
- Conifers
- Cycads
- Gingkophytes
- Gnetophytes
Conifers are the dominant phylum of gymnosperms, with the greatest variety of species (Figure 2). Typical conifers are tall trees that bear scale-like or needle-like leaves. Water evaporation from leaves is reduced by their narrow shape and a thick cuticle. Snow easily slides off needle-shaped leaves, keeping the snow load light, thus reducing brok...
Cycadsthrive in mild climates, and are often mistaken for palms because of the shape of their large, compound leaves. Cycads bear large strobili or cones (Figure 3), and may be pollinated by beetles rather than wind, which is unusual for a gymnosperm. Large cycads dominated the landscape during the age of dinosaurs in the Mesozoic, but only a hundr...
The single surviving species of the ginkgophytes group is Ginkgo biloba (Figure 4). Its fan-shaped leaves—unique among seed plants because they feature a dichotomous venation pattern—turn yellow in autumn and fall from the tree. For centuries, G. bilobawas cultivated by Chinese Buddhist monks in monasteries, which ensured its preservation. It is pl...
The phylogenetic position of the gnetophytes is not currently resolved. Their possession of vessel elements suggests they are the closest relative to modern angiosperms. However, molecular analysis places them closer to the conifers. The three living genera are quite dissimilar: Ephedra, Gnetum, and Welwitschia (Figure 5), which may indicate that t...
All gymnosperms are heterosporous. The male and female reproductive organs can form in cones or strobili. Male and female sporangia are produced either on the same plant, described as monoecious (“one home” or bisexual), or on separate plants, referred to as dioecious (“two homes” or unisexual) plants.
Oct 31, 2023 · Gymnosperms produce both male and female cones, each making the gametes needed for fertilization; this makes them heterosporous. Megaspores made in cones develop into the female gametophytes inside the ovules of gymnosperms, while pollen grains develop from cones that produce microspores.
All gymnosperms are heterosporous. The male and female reproductive organs can form in cones or strobili. Male and female sporangia are produced either on the same plant, described as monoecious (“one home” or bisexual), or on separate plants, referred to as dioecious (“two homes” or unisexual) plants.
Gymnosperms, meaning “naked seeds,” are a diverse group of seed plants. According to the “anthophyte” hypothesis, the angiosperms are a sister group of one group of gymnosperms (the Gnetales), which makes the gymnosperms a paraphyletic group.
Gymnosperms. Gymnosperms (“naked seed”) are a diverse group of seed plants and are paraphyletic. Paraphyletic groups do not include descendants of a single common ancestor. Gymnosperm characteristics include naked seeds, separate female and male gametes, pollination by wind, and tracheids, which transport water and solutes in the vascular ...
