| 单词 | gymnosperm |
| 例句 | Edward collected the state’s angiosperms and gymnosperms in an herbarium, and Orra drew and painted them. Mushrooms, Magma and Love in a Time of Science 2018-07-26T04:00:00Z Seed plants are in the Spermatophyte group and consist of gymnosperms and angiosperms. Fundamentals of Biology 2015-01-01T00:00:00Z Like all gymnosperms, pines are heterosporous and produce male microspores and female megaspores. Concepts of Biology 2013-04-25T00:00:00Z This means of pollination is much more efficient than the wind pollination of most gymnosperms. Miller & Levine Biology 2018-01-01T00:00:00Z For example, the unusual gymnosperm Welwitschia mirabilis is the only extant species of an entire order of plants. Environmental Biology 2018-09-06T00:00:00Z They reproduce via seeds, as do the evolutionarily older gymnosperms, which include pine trees, ginkgoes, and others. Exquisite fossils unearthed in Inner Mongolia reveal how peas got their hard coat 2021-05-26T04:00:00Z The lifecycle of bryophytes and pterophytes is characterized by the alternation of generations, like gymnosperms and angiosperms; what sets bryophytes and pterophytes apart from gymnosperms and angiosperms is their reproductive requirement for water. Fundamentals of Biology 2015-01-01T00:00:00Z Like angiosperms, but unlike other gymnosperms, all gnetophytes possess vessel elements in their xylem. Concepts of Biology 2013-04-25T00:00:00Z In gymnosperms and dicots, vascular bundles are arranged in a ring. Miller & Levine Biology 2018-01-01T00:00:00Z "Why isn't there a gradual evolution of the angiosperms? Why can't we see intermediate forms between the gymnosperms - things like conifers - and the flowering plants? And why, when they appear, are they already so diverse?" New light shed on Charles Darwin's 'abominable mystery' 2021-01-22T05:00:00Z Angiosperms evolved from gymnosperms, but how carpels and the second seed coat arose has been a big mystery. Exquisite fossils unearthed in Inner Mongolia reveal how peas got their hard coat 2021-05-26T04:00:00Z The Ginkgoales, a group of gymnosperms with only one surviving species—the Ginkgo biloba—were the first gymnosperms to appear during the lower Jurassic. Fundamentals of Biology 2015-01-01T00:00:00Z What are the four modern-day groups of gymnosperms? Concepts of Biology 2013-04-25T00:00:00Z Other amber specimens from the same ancient forest show pollen from an older group of trees, the gymnosperms—conifers and gingkoes—which today are pollinated largely by wind. Fossils in Burmese amber offer an exquisite view of dinosaur times—and an ethical minefield 2019-05-23T04:00:00Z Other plants, including conifers, ferns and algae, are known as gymnosperms. New light shed on Charles Darwin's 'abominable mystery' 2021-01-22T05:00:00Z Crisscrossing the valley over the past 2 decades, Verma has rescued dozens of fossilized dinosaur nests and hundreds of eggs, along with thousands of other specimens, including rare extinct sharks and a fossilized gymnosperm forest. India’s paleontologists fight destruction of its fossil riches 2018-04-04T04:00:00Z The life cycle of a conifer will serve as our example of reproduction in gymnosperms. Fundamentals of Biology 2015-01-01T00:00:00Z They bear large cones, and unusually for gymnosperms, may be pollinated by beetles, rather than wind. Concepts of Biology 2013-04-25T00:00:00Z The Jurassic was a world dominated by gymnosperm plants, such as conifers, which produced sugary nectar to capture pollen from the air. Butterfly origins pushed back in time 2018-01-10T05:00:00Z Northbound trees were usually gymnosperms, which are mostly conifers in North America. Trees in eastern US head west as climate changes 2017-05-16T04:00:00Z He and his colleagues therefore sequenced just the genes—which are just a small fraction of the total DNA—for 24 gymnosperms and three other plants. Why is your Christmas tree so big? An ancient gift of extra genes 2015-11-20T05:00:00Z Like all gymnosperms, pines are heterosporous and generate two different types of spores: male microspores and female megaspores. Fundamentals of Biology 2015-01-01T00:00:00Z Like cycads — their gymnosperm relatives — and ferns, the ginkgo produces motile sperm. The Female Ginkgo Tree’s Acrid Smell of Success 2015-10-29T04:00:00Z Figure 2: Conifer genomes contain expansions of a diverse set of LTR-RTs. a, Distribution of different classes of transposable elements from six gymnosperm species. The Norway spruce genome sequence and conifer genome evolution 2013-05-29T17:21:22.577Z He explained that data gaps remained: "The coverage of early diverging plants is still from optimal, with many large and important groups still badly sampled - for example, gymnosperms and ferns." Tulip trees are 'molecular fossils' 2013-04-16T07:10:58Z Jensen and Zwieniecki considered only flowering plants, or angiosperms, such as maples and oaks, but not gymnosperms, such as pines and redwoods. Simple Physics May Limit the Size of Leaves 2013-01-04T17:10:00Z The evolution of plants has resulted in widely varying levels of complexity, from the earliest algal mats, to bryophytes, lycopods, and ferns, to the complex gymnosperms and angiosperms of today. Fundamentals of Biology 2015-01-01T00:00:00Z Overall, flowering plants—the angiosperms—were at greater risk than pine trees and their relatives—the gymnosperms. Trees Living on the Edge 2012-11-21T18:00:00Z The xylem tissue of most gymnosperms comprises a single water-transporting cell type, tracheids. The Norway spruce genome sequence and conifer genome evolution 2013-05-29T17:21:22.577Z The oak, apple, beech, etc., are angiosperms, while the pines, spruce, hemlock, and the allied varieties, are gymnosperms. Webster's Unabridged Dictionary 2012-03-24T02:00:23.513Z Some of these relationships date back to 300 million years ago, when the first gymnosperms, the group that includes pines and ginkgos,- appeared. Green Blog: The Tree of Life Gets a Makeover 2011-12-19T21:11:21Z That algal line evolved into the Charophytes, and eventually into the modern mosses, ferns, gymnosperms, and angiosperms. Fundamentals of Biology 2015-01-01T00:00:00Z In many gymnosperms more than two cotyledons are present, and they are arranged in a whorl. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z Two major differences between angiosperms and gymnosperms are their contrasting reproductive development and the development of water-conducting xylem cells. The Norway spruce genome sequence and conifer genome evolution 2013-05-29T17:21:22.577Z In gymnosperms the pollen-tubes, having penetrated a certain distance down the tissue of the nucellus, are usually arrested in growth for a longer or shorter period, sometimes nearly a year. Encyclopaedia Britannica, 11th Edition, Volume 10, Slice 5 "Fleury, Claude" to "Foraker" 2011-04-03T02:00:20.883Z The former are angiosperms, and constitute the principal part of the species; the latter are gymnosperms, and chiefly consist of the Conifer� and Cycadace�. The New Gresham Encyclopedia. Vol. 1 Part 2 Amiel to Atrauli The life cycle of a gymnosperm involves alternation of generations, with a dominant sporophyte in which the female gametophyte resides, and reduced gametophytes. Fundamentals of Biology 2015-01-01T00:00:00Z The endosperm formed in the embryo-sac of angiosperms after fertilization, and found previous to it in gymnosperms, consists of cells containing nitrogenous and starchy or fatty matter, destined for the nutriment of the embryo. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z Figure 2: Conifer genomes contain expansions of a diverse set of LTR-RTs. a, Distribution of different classes of transposable elements from six gymnosperm species. The Norway spruce genome sequence and conifer genome evolution 2013-05-29T17:21:22.577Z They are also called gymnosperms, the seeds in like manner not being inclosed in a pericarp. Principles of Geology or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of Geology We have this principle exemplified in the Carboniferous flora, by the magnitude of its arborescent club-mosses, and the vast variety of its gymnosperms. The Origin of the World According to Revelation and Science Watch this video to see the process of seed production in gymnosperms. Fundamentals of Biology 2015-01-01T00:00:00Z These gymnosperms are also characterized by having such peculiar and inconspicuous flowers that the ordinary observer would hardly apply that term to denote their floral organs. The Contemporary Review, Volume 36, September 1879 I neither care to know or tell whether the shrubs and trees in my evergreen pictures are angiosperms or gymnosperms; we have no 'transportation' for text books for students! The Continental Monthly, Vol. 4, No. 2, August, 1863 Devoted to Literature and National Policy All of the gymnosperms of the northern United States belong to the second order, but representatives of the others are found in the southern and southwestern states. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Phanerogamic plants in their lowest groups of gymnosperm exogens then begin to appear in the Devonian conifers, gradually followed by cycads. Creation and Its Records All angiosperms have seeds that are covered or protected: this feature separates them from the ‘naked seeds’ of gymnosperms. Fundamentals of Biology 2015-01-01T00:00:00Z Their seeds are, from their first appearance, in a very different condition from those of gymnosperms, and their flowers are generally conspicuous. The Contemporary Review, Volume 36, September 1879 This is precisely analogous to the case of gymnosperms, lycopods, etc., where on leaf structures are formed macro and micro sporangia. Scientific American Supplement, No. 531, March 6, 1886 Their flowers are rather more highly differentiated than those of the other gymnosperms, and are said to show some approach in structure to those of the angiosperms. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses It is thought by some that the gymnosperms had their station on the drier plains and higher lands. The Elements of Geology The male and female gametophyte structures are present on separate male and female cones in gymnosperms, whereas in angiosperms, they are a part of the flower. Fundamentals of Biology 2015-01-01T00:00:00Z Lastly, wind plays an important role in pollination in gymnosperms because pollen is blown by the wind to land on the female cones. Fundamentals of Biology 2015-01-01T00:00:00Z The diploid sporophyte of angiosperms and gymnosperms is the conspicuous and long-lived stage of the life cycle. Fundamentals of Biology 2015-01-01T00:00:00Z The first root of the seedling plant continues here as the main root of the plant, as was the case with the gymnosperms, but not with the monocotyledons. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Many of the fernlike forms, however, have distinct affinities with the cycads, of which they may be the ancestors, and some bear seeds and must be classed as gymnosperms. The Elements of Geology In angiosperms, the female gametophyte exists in an enclosed structure—the ovule—which is within the ovary; in gymnosperms, the female gametophyte is present on exposed bracts of the female cone. Fundamentals of Biology 2015-01-01T00:00:00Z Because the pollen is shed and blown by the wind, this arrangement makes it difficult for a gymnosperm to self-pollinate. Fundamentals of Biology 2015-01-01T00:00:00Z Once the seed is ready to be dispersed, the bracts of the female cones open to allow the dispersal of seed; no fruit formation takes place because gymnosperm seeds have no covering. Fundamentals of Biology 2015-01-01T00:00:00Z Each one now divides in precisely the same way as in the ferns and gymnosperms, into four pollen spores. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses These gymnosperms, related to the pines and spruces in structure and fruiting, but palmlike in their foliage, and uncoiling their long leaves after the manner of ferns, culminated in the Jurassic. The Elements of Geology Double fertilization is a key event in the lifecycle of angiosperms, but is completely absent in gymnosperms. Fundamentals of Biology 2015-01-01T00:00:00Z These are named respectively “gymnosperms” and “angiosperms,” and to the first our plant belongs. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Other gymnosperms were related to the yews, and it was by these that many of the fossil nuts found in the Coal Measures were borne. The Elements of Geology |
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