Liverwort Prothallus

A prothallium, or prothallus; from Latin pro = forwards and Greek θαλλος (thallos) = twig; is usually a pteridophyte, i.e. spore-bearing plant, (almost exclusively ferns) in gametophyte stage in the alternation of generations cycle. Occasionally the term is also used to describe the young gametophyte of a liverwort or peat moss as well. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... The pteridophytes are vascular plants (plants with xylem and phloem) that neither flower nor produce seeds. ... Classes Psilotopsida Equisetopsida Marattiopsida Polypodiopsida A fern is any one of a group of about 20,000 species of plants classified in the phylum or division Pteridophyta, also known as Filicophyta. ... In plants that undergo alternation of generations, a gametophyte is the structure, or phase of life, that contains only half of the total complement of chromosomes: The sporophyte produces spores, in a process called meiosis. ... Sporic or diplohaplontic life cycle. ... Orders Haplomitriales Sphaerocarpales Marchantiales Metzgeriales Monocleales Jungermanniales Takakiales Liverworts are non-vascular plants, also called hepatics (scientific name Hepaticophyta). ... Species See text. ...

The prothallium of a pteridophyte forms from a spore that has fallen from the sporophyte stage and germinated. It is a short-lived and inconspicuous heart-shaped structure typically 2-5 millimeters wide, with a number of rhizoids (root-like hairs) growing underneath, and the sex organs: archegonium (female) and antheridium (male). Appearance varies quite a lot between species. Some are green and conduct photosynthesis while others are colorless and nourish themselves underground as saprotrophs. This article is about a biological reproductive structure; for the video game, see Spore (video game). ... In plants that undergo alternation of generations, a sporophyte is the structure, or phase of life, that contains a total complement of chromosomes: The sporophyte produces spores, in a process called meiosis. ... Sunflower seedlings, just three days after germination Germination is the process where growth emerges from a period of dormancy. ... Rhizoids, in fungi, are small branching hyphae that grow downwards from the stolons that anchor the fungus. ... An archegonium (pl: archegonia) (from the Greek arche = beginning and gonos = born) is a multicellular structure or organ of the gametophyte phase of certain plants producing and containing the ovum or female gamete. ... Diagram of antheridium anatomy An antheridium (plural: antheridia) is a structure or organ of the gametophyte phase of certain plants producing and containing the spermatids or male gametes. ... The leaf is the primary site of photosynthesis in plants. ... A Saprotroph (or saprobe) is an organism that obtains its nutrients from non-living organic matter, usually dead and decaying plant or animal matter, by absorbing soluble organic compounds. ...

Prothallus of the tree fern Dicksonia antarctica (note new moss plants for scale)

Image File history File linksMetadata Size of this preview: 766 × 599 pixel Image in higher resolution (1449 × 1134 pixel, file size: 316 KB, MIME type: image/jpeg) Prothallus of Dicksonia antarctica File links The following pages on the English Wikipedia link to this file (pages on other projects are not... Image File history File linksMetadata Size of this preview: 766 × 599 pixel Image in higher resolution (1449 × 1134 pixel, file size: 316 KB, MIME type: image/jpeg) Prothallus of Dicksonia antarctica File links The following pages on the English Wikipedia link to this file (pages on other projects are not... Binomial name Dicksonia antarctica Dicksonia antarctica, known commonly as the Tasmanian Tree Fern, Soft Tree Fern, or the Man Fern, is an evergreen tree fern native to parts of Australia, namely New South Wales, Tasmania, and Victoria. ... Subclasses Sphagnidae Andreaeidae Tetraphidae Polytrichidae Archidiidae Buxbaumiidae Bryidae Mosses are small, soft plants that are typically 1-10 cm tall, occasionally more. ...

Alternation of Generations

Spore-bearing plants, like all plants, go through a life-cycle of alternation of generations. The fully grown sporophyte, what the layman refers to as the fern, produces genetically unique spores in the sori by meiosis. The haploid spores fall from the sporophyte and germinate by mitosis, given the right conditions, into the gametophyte stage, the prothallus. The prothallus then develops independently for several weeks; it grows sex organs and produces ova and flagellated sperm. After rainfall, the sperm are able to swim to the ova for fertilization to form a diploid sporophyte cell. This cell divides by mitosis and grows out of the gametophyte into a new fern, which will produce new spores that will grow into new prothallia etc., thus completing the life cycle of the organism. The pteridophytes are vascular plants (plants with xylem and phloem) that neither flower nor produce seeds. ... Sporic or diplohaplontic life cycle. ... In plants that undergo alternation of generations, a sporophyte is the structure, or phase of life, that contains a total complement of chromosomes: The sporophyte produces spores, in a process called meiosis. ... Classes Psilotopsida Equisetopsida Marattiopsida Polypodiopsida A fern is any one of a group of about 20,000 species of plants classified in the phylum or division Pteridophyta, also known as Filicophyta. ... This article is about a biological reproductive structure; for the video game, see Spore (video game). ... Sori on the underside of a curling fern. ... Not to be confused with miosis. ... Haploid (meaning simple in Greek) cells have only one copy of each chromosome. ... Mitosis divides genetic information during cell division. ... In plants that undergo alternation of generations, a gametophyte is the structure, or phase of life, that contains only half of the total complement of chromosomes: The sporophyte produces spores, in a process called meiosis. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... The signifier sperm can refer to: (mass noun, from Greek sperma = seed) a substance which consists of spermatozoa and which is a component of semen (mass noun) semen itself (informally, count noun with plural sperm or sperms) a single spermatozoon (= sperm cell) sperma ceti (Latin ceti, genitive of cetus = whale... Categories: Biology stubs ... Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ... In plants that undergo alternation of generations, a sporophyte is the structure, or phase of life, that contains a total complement of chromosomes: The sporophyte produces spores, in a process called meiosis. ... In plants that undergo alternation of generations, a gametophyte is the structure, or phase of life, that contains only half of the total complement of chromosomes: The sporophyte produces spores, in a process called meiosis. ... This article or section does not cite its references or sources. ...

Advantages of Alternation of Generations

There are two important evolutionary advantages to the alternation of generations plant life-cycle. Firstly, by forming a haploid gametophyte, there is only one allele for any genetic trait. Thus, all alleles will be expressed because no allele may be masked by a dominant counterpart (there is no counterpart). The benefit of this is that any mutation that causes a lethal, or harmful, trait expression cannot be masked and will cause the gametophyte to die; thus, the trait cannot be passed on to future generations, preserving the strength of the gene pool. Also, crossing-over during meiosis in the formation of spores, and sexual reproduction in the gametophytes, allows for genetic diversity, which also inhibits harmful recessive genes from "surfacing" and being expressed. Sporic or diplohaplontic life cycle. ... For the hard rock band, see Allele (band). ... This article or section does not adequately cite its references or sources. ... In genetics, dominant allele refers to a genetic feature that hides the recessive allele. ... Not to be confused with miosis. ... Not to be confused with miosis. ...   Sexual reproduction is a type of reproduction that results in increasing genetic diversity of the offspring. ... This article or section does not adequately cite its references or sources. ...

External links

• Liverwort Sporophyte
• Fern Life-Cycle