Why gymnosperms are largest and oldest plants

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Search for:. Animal Cells. Transcription and translation. Prokaryotic cells. Molecules of life. Genetic inheritance. Introduction to Biology. They are typically slow to reproduce; up to a year may pass between pollination and fertilization, and seed maturation may require 3 years. All gymnosperms are heterosporous and have two types of cones: male, which are smaller and female, which tend to be larger. Seeds: structure formed by the maturation of the ovule in seed plant; in fact the seeds represent a portion of the life cycle involving 3 generations of plants mother sporophyte, megagametophyte, and new sporophyte or embryo.

The oldest known seedlike structures are from the late Devonian period around million years ago. Seeds seem to be one of the factors responsible for the dominance of seed plants in today's flora. Disadvantages, when compared to pteridophytes, include 1 expensive to make, so fewer are produced and 2 heavier, so not as easily dispersed.

Thus, the loss of flagella on sperm is lost eventually within the gymnosperms. With the exception of the cycads and some gnetophytes, gymnosperms are pollinated by wind. Palm-like plants found mainly in tropical and subtropical regions. First appeared about million years ago during the Carboniferous; were so numerous during the Mesozoic that is it often called the Age of Cycads and Dinosaurs.

Many have a distinct trunk, with the functional leaves at the top - these being large megaphylls, often dissected. Reproduction structures are reduced leaves with sporangia attached loosely or tightly clustered into conelike structures near the apex of the plant. Species are either dioecious male and female sporangia on different plants or monoecious male and female sporangia on same plant. Plants are often toxic with neurotoxins and carcinogenic compounds.

One species: Ginkgo biloba ; the maidenfern tree no longer living in the wild, and only found in cultivation. The tree was preserved in temple grounds in China and Japan. The genus is known from fossils that date back nearly million years and are nearly identical to present-date trees.

It is easily recognized by its fan-shaped leaves and dichotomous pattern of vein; the leaves on the spur shoots are more or less entire, whereas the those on the long shoots and seedlings are deeply lobed. Unlike most of gymnosperms, this is a deciduous tree. The species is dioecious: the ovulate trees produce an abundance of trees which have a particularly obnoxious odor. One of few species of plants known to have sex chromosomes.

First brought over to the U. The species is also widely used in the ethnomedicinal trade. Vessel-bearing gymnosperms, but apparently the vessels are convergent with angiosperms. Molecular systematic evidence is suggesting these are closely related if not imbedded in conifers, rather than close to angiosperms as usually assumed.

Three families each with a single genus, none of which are found in Wisconsin. Gnetum : 30 species of trees and climbing vines, with large leathery leaves that resemble dicots Ephedra or mormon tea with about 35 species, profusely branched shrubs with small scalelike leaves Welwitschia is one of the most bizarre organisms - most of the plant is buried in sandy soil of the coastal desert of southwestern Africa.

The exposed part consists of a massive woody, concave disk that produces only two strap-shaped leaves with the cone bearing branches arising from meristematic tissue on the margin of disk.

Known from the late Carboniferous, some million years ago. Now dominant only in boreal forests and often found in higher elevations, but as a group they also do well in dry environments. Pines, spruces, and firs are of great commercial value. The tallest coastal redwood , most massive giant sequoia , and oldest bristle cone pine are members of this group.

All 3 families and 13 species of gymnosperms found in Wisconsin belong to this group:. Cupressaceae - cypress family. This is a misnomer. Ferns do not bear seeds. These plants were some of the earliest gymnosperms which have long been extinct. The gymnosperms include the oldest and largest trees known. The Bristle Cone Pines, some over years old are the oldest living plants. The Giant Redwoods are over m tall - the tallest plants known.

Both are native to California.