The Origin and Evolution of Plants 108 Exercise D: Seed Plants Ginkgo There is o

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The Origin and Evolution of Plants 108 Exercise D: Seed Plants Ginkgo There is only one species of ginkgo present on Earth perplexing group of plants. Gne (Ginkgo biloba), and it appears nearly identical to Ginkgo trees (Class Ginkgoopsida) are living fossils Gnetophiytes (Class Gnetopsida) are a very of three genera, which are highly variable in their Is 270 million years old. Ginkgo biloba is the only overall morpholoey and distribution. Perhaps the strangest plant on the planet is the welwitschia example of a broad-leafed, deciduous gymnosperm tree. All other gymnosperm trees are needle-like, evergreen conifers. Interestingly, we believe that ginkgos became extinct in the wild, but monks in eastern China protected the lineage of this living (Welwitschio mirabilis) It is considered a living fossil with a very strange growth habit. Following germination, the two cotyledons (seed leaves) give rise to two true leaves. Those leaves continue to fossil by cultivating them in their monasteries. There grow throughout the life of the plant reaching are a few populations of ginkgos that exist in the wild upwards of 6 meters, and no new leaves are presently. However, the genetic variation of these produced populations is very limited, indicating they may be populations that have taken a hold from just a few U trees. It is hypothesized that monks may have planted the parental trees, naturalizing these semi- wild populations. nlike all other gymnosperms, gnetophytes have vessel elements. Vessel elements are vascular tissue that are much more efficient at transporting water than tracheids. While all vascular plants have tracheids, only gnetophytes and flowering plants (Angiosperms) have vessel elements (Fig. 2). This similarity in morphology led early botanists to assume that flowering plants are all descendants of gnetophytes. Also similar to flowering plants, some species of gnetophytes (i.e. welwitschia) are pollinated by insects attracted to nectar in the male and female strobili. All other gymnosperms are wind- pollinated. However, modern genetic analysis suggests that gnetophytes are not closely related to angiosperms, regardless of these morphological and ecological relationships 17. Draw a ginkgo leaf and seed. 18a. What morphological characteristic do gnetophytes share with flowering plants? Conifers Conifers (Class Pinopsida) are a diverse group of gymnosperms with linear or scaly evergreen leaves that bear seeds within cones. Most conifers are large trees, but a few are shrubs. The world's tallest tree is a conifer known as coastal redwood (Sequoia sempervirens), and it can grow more than 100 meters. The oldest living tree (estimated to be 4,700 years old ) is also a conifer known as Great Basin Bristlecone Pine (Pinus longaeva). This particular tree germinated around the construction of the very first Egyptian stone pyramids! It's location is kept secret. 18b. What ecological characteristic do gnetophytes share with flowering plants? http://thebiologyprimer.com/the-origin-and-evolution-of-plan

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18. a.

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