| Asterotheca Temporal range: Carboniferous to Triassic | |
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| Asterotheca cyathea | |
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| Genus: | Asterotheca |
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Asterotheca is a genus of seedless, spore-bearing, vascularized ferns dating from the Carboniferous of the Paleozoic to the Triassic of the Mesozoic.
Asterotheca sp. is a vascularized, seedless fern that reproduces via spores that require the presence of water. This genus of fern lived from the Carboniferous to the Triassic and is an ancestor to all modern seed plants.
The leaves of Asterotheca (and all ferns) are called fronds. [1] Fossilized specimens show large, morphologically complex structures that consist of leaf segments called pinnae. [2] Each pinna consists of four to eight sporangia. Asterotheca fronds are unipinnate because there is only a single row of pinnae on each side of the rachis, or main central stem.
Asterotheca cyathea displays open dichotomous unipinnate segments, each with four to five eusporangia.
In the field of paleobotany, different parts of plant fossils are assigned different taxonomic names based on how they are preserved.
Synonyms for Asterotheca include:
True ferns (Filicales) are vascular plants that reproduce by way of spores that require water to disperse their gametophytes. Families of ferns are classified according to the arrangement and morphology of their sporangia and are generally categorized into two groups: the eusporangia and leptosprangia. Asterotheca exhibited eusporangia that are partially fused within a larger synangium that is most commonly characterized with four to eight sporangia.
The reproduction cycle of Asterotheca, like that of all seedless ferns, is an alternation of generations. In this life cycle, there is an alternation between two different forms (gametophytes and sporophytes) that are alternately sexual and asexual.
The alternation of generations in ferns can be generalized in five steps: [3]
A - Asterotheca. 1, Pinnule bearing 8 synangia. 2, Synangium in side view. 3, In section, magnified.
B - Renaultia. 1, Fertile pinnule, nat size. 2, Sporangium, enlarged.
C - Dactylotheca, as in B.
D - Sturiella. Section of pinnule and synangium. a, Vascular bundle; c, hairs; b, d, annulus, magnified.
E - Oligocarpia. Sorus in surface-view, magnified.
F - Crossotheca. Fertile pinnule, bearing several tufts of microsporangia, magnified.
G - Senftenbergia. Group of annulate sporangia, magnified.
H - Hawlea. Synangium after dehiscence, magnified.
J - Urnatopteris. 1, Part of fertile pinna, nat. size. 2, Sporangia, showing apical pores, magnified.
Of the above. A, D, E, G and H, probably belong to true Ferns; F is the male fructification of a Pteridosperm (Lyginodendron); the rest are of doubtful nature.
The evolution of vascular plants with roots and leaves during the Devonian and early Carboniferous increased the rate of photosynthesis, and, thus, increased the rate of CO2 removal from the Earth's atmosphere by almost a factor of five during the Carboniferous. [3]
Asterotheca, like all seedless ferns, requires an environment with abundant water for survival. Suitable paleoenvironments include tropical everwet, tropical summerwet, warm temperate, and cool temperate biomes. [4]
A gametophyte is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte. The sporophyte can produce haploid spores by meiosis that on germination produce a new generation of gametophytes.
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, fungi and protozoa. They were thought to have appeared as early as the mid-late Ordovician period as an adaptation of early land plants.
A sporangium ; pl.: sporangia) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other groups form sporangia at some point in their life cycle. Sporangia can produce spores by mitosis, but in land plants and many fungi, sporangia produce genetically distinct haploid spores by meiosis.
The ferns are a group of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the branched sporophyte is the dominant phase.
Alternation of generations is the predominant type of life cycle in plants and algae. In plants both phases are multicellular: the haploid sexual phase – the gametophyte – alternates with a diploid asexual phase – the sporophyte.
Bryophytes are a group of land plants, sometimes treated as a taxonomic division, that contains three groups of non-vascular land plants (embryophytes): the liverworts, hornworts, and mosses. In the strict sense, Bryophyta consists of the mosses only. Bryophytes are characteristically limited in size and prefer moist habitats although they can survive in drier environments. The bryophytes consist of about 20,000 plant species. Bryophytes produce enclosed reproductive structures, but they do not produce flowers or seeds. They reproduce sexually by spores and asexually by fragmentation or the production of gemmae. Though bryophytes were considered a paraphyletic group in recent years, almost all of the most recent phylogenetic evidence supports the monophyly of this group, as originally classified by Wilhelm Schimper in 1879. The term bryophyte comes from Ancient Greek βρύον (brúon) 'tree moss, liverwort', and φυτόν (phutón) 'plant'.
The embryophytes are a clade of plants, also known as Embryophyta or land plants. They are the most familiar group of photoautotrophs that make up the vegetation on Earth's dry lands and wetlands. Embryophytes have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of freshwater charophyte green algae as a sister taxon of Charophyceae, Coleochaetophyceae and Zygnematophyceae. Embryophytes consist of the bryophytes and the polysporangiophytes. Living embryophytes include hornworts, liverworts, mosses, lycophytes, ferns, gymnosperms and angiosperms. Embryophytes have diplobiontic life cycles.
In biology, a biological life cycle is a series of stages of the life of an organism, that begins as a zygote, often in an egg, and concludes as an adult that reproduces, producing an offspring in the form of a new zygote which then itself goes through the same series of stages, the process repeating in a cyclic fashion.
A sporophyte is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase.
A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the large leaves of cycads, as well as palms (Arecaceae) and various other flowering plants, such as mimosa or sumac. "Frond" is commonly used to identify a large, compound leaf, but if the term is used botanically to refer to the leaves of ferns and algae it may be applied to smaller and undivided leaves.
Gymnocarpium dryopteris, the western oakfern, common oak fern, oak fern, or northern oak fern, is a deciduous fern of the family Cystopteridaceae. It is widespread across much of North America and Eurasia. It has been found in Canada, the United States, Greenland, China, Japan, Korea, Russia, and most of Europe. It is a seedless, vascular plant that reproduces via spores and have a life cycle with alternating, free-living sporophyte and gametophyte phases.
Microspores are land plant spores that develop into male gametophytes, whereas megaspores develop into female gametophytes. The male gametophyte gives rise to sperm cells, which are used for fertilization of an egg cell to form a zygote. Megaspores are structures that are part of the alternation of generations in many seedless vascular cryptogams, all gymnosperms and all angiosperms. Plants with heterosporous life cycles using microspores and megaspores arose independently in several plant groups during the Devonian period. Microspores are haploid, and are produced from diploid microsporocytes by meiosis.
A prothallus, or prothallium, is usually the gametophyte stage in the life of a fern or other pteridophyte. Occasionally the term is also used to describe the young gametophyte of a liverwort or peat moss as well. In lichens it refers to the region of the thallus that is free of algae.
Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from either parent. Asexual reproduction produces new individuals without the fusion of gametes, resulting in clonal plants that are genetically identical to the parent plant and each other, unless mutations occur.
Sporogenesis is the production of spores in biology. The term is also used to refer to the process of reproduction via spores. Reproductive spores were found to be formed in eukaryotic organisms, such as plants, algae and fungi, during their normal reproductive life cycle. Dormant spores are formed, for example by certain fungi and algae, primarily in response to unfavorable growing conditions. Most eukaryotic spores are haploid and form through cell division, though some types are diploid sor dikaryons and form through cell fusion.we can also say this type of reproduction as single pollination
Ceratopteris is the only genus among homosporous ferns that is exclusively aquatic. It is pan-tropical and classified in the Parkerioideae subfamily of the family Pteridaceae.
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes.
Diplazium australe, commonly known as the Austral lady fern, is a small fern occurring in eastern Australia, New Zealand and Norfolk Island. The habitat is moist shaded areas, often occurring in rainforest.
Asplenium resiliens, the blackstem spleenwort or little ebony spleenwort, is a species of fern native to the Western Hemisphere, ranging from the southern United States south to Uruguay, including parts of the Caribbean. Found on limestone substrates, it is named for its distinctive purplish-black stipe and rachis. A triploid, it is incapable of sexual reproduction and produces spores apogamously. First described by Martens and Galeotti in 1842 under the previously used name Asplenium parvulum, the species was given its current, valid name by Kunze in 1844. Several similar species are known from the tropics; A. resiliens may have arisen from these species by reticulate evolution, but precise relationships among the group are not yet certain.
Asplenium tutwilerae is a rare epipetric fern found only in Hale County, Alabama, United States. A. tutwilerae is a fertile allotetraploid, formed by the chromosomal doubling of a specimen of the sterile diploid A. × ebenoides, a hybrid of A. platyneuron and A. rhizophyllum. Except for its spores, which are fertile rather than malformed, A. tutwilerae is essentially identical to A. × ebenoides and was described as part of that species until 2007. It is named in honor of Julia Tutwiler, who discovered the only known wild population at Havana Glen in 1873.
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