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Lab 10: Land Plants - An Evolutionary Overview
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Phylogeny of Seed Plants
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Coniferophyta – Conifers
Conifers are the largest and most ecologically and economically important group of
“gymnosperms”. Pines (Pinus spp.),
firs (Abies spp.), cypresses (Cupressus spp.), spruces (Picea spp.), and redwoods (Sequoia and Sequoiadendron spp.) are all familiar and valued trees. Members of this group are called conifers because most bear their seeds in cones, whose woody or leathery scales and bracts protect the ovules and seeds. In some genera, such as Juniperus (junipers), the cone scales are fleshy and often brightly colored, making the cones berry-like.
Conifers date back to the Carboniferous, some 300 million years ago. Today, they remain important in cooler regions of the Earth, such as in the boreal forests of North America and Asia, where species of Pinus, Picea, and Abies are the dominant vegetation over large areas. Some conifer groups, such as the Araucariaceae and Podocarpaceae, are only found in the Southern Hemisphere. Conifers are often referred to as "evergreens" because of the persistent foliage in most species, and as "softwoods" because their wood is softer than that of many anthophyte trees. Conifers generally exhibit monopodial branching, with a dominant central shoot or trunk from which lateral branches arise, as opposed to the dichotomous branching seen in some other groups. Conifers are heterosporous (as are all seed plants), with separate male and female strobili.
Conifers include over 600 species, in 65 genera and 7 families. Four of those families, the Pinaceae, Cupressaceae, Podocarpaceae, and Taxaceae, contain 90% of the species.
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Araucariaceae | ||
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