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| | + | [[Image:Fern spores P1180804.jpg|thumb|Fern sori, clusters of meiosporangia on the underside of the leaf]] |
| | [[Image:Sporic meiosis.png|thumb|Spores produced in a sporic life cycle.]] | | [[Image:Sporic meiosis.png|thumb|Spores produced in a sporic life cycle.]] |
| | + | A simple reproductive body, usually composed of a single detached cell, and containing no [[embryo]].{{SCH}} |
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| − | In [[biology]], a '''spore''' is a [[reproduction|reproductive]] structure that is adapted for [[biological dispersal|dispersion]] and surviving for extended periods of time in unfavorable conditions. Spores form part of the [[Biological life cycle|life cycles]] of many [[plant]]s, [[algae]], [[fungus|fungi]] and some [[protozoan]]s.
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| − | Spores are usually [[haploid]] and [[unicellular]] and are produced by [[meiosis]] in the [[sporophyte]]. Once conditions are favorable, the spore can develop into a new [[organism]] using [[mitosis|mitotic]] division, producing a [[multicellular]] [[gametophyte]], which will eventually go on to produce [[gamete]]s. Two gametes fuse to create a new sporophyte. This cycle is known as [[alternation of generations]] however "Biological Life Cycle" is a better term as there may be more than one phase and it cannot therefore be an "alteration" of anything. Haploid spores produced by [[mitosis]] (known as [[mitospore]]s) are used by many fungi for asexual reproduction.
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| − | It is useful to contrast spores with gametes: spores are the units of ''asexual'' reproduction as a single spore develops into a new organism; gametes are the units of ''sexual'' reproduction as two gametes need to fuse to create a new organism.
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| − | The term ''spore'' may also refer to the dormant stage of some [[bacterium|bacteria]] or [[archaea]]; however these are more correctly known as [[endospore]]s and are not truly spores in the sense discussed in this article. The term can also be loosely applied to some [[animal]] resting stages. Fungi that produce spores are known as ''sporogenous'', and those that do not are ''asporogenous''.
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| − | The term derives from the [[ancient Greek]] word σπορα, meaning [[seed]].
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| − | ==Classification of spores==
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| − | Spores can be classified in several manners.
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| − | ===By function===
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| − | [[Image:Fern spores P1180804.jpg|thumb|Fern sori, clusters of meiosporangia on the underside of the leaf]]
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| − | [[Diaspores]] are dispersal units of [[fungi]], [[moss]]es, [[fern]]s, [[fern allies]], and some other [[plant]]s. In fungi, [[chlamydospore]]s are thick-walled resting spores, and [[zygospores]] are thick-walled resting spores (hypno[[zygote]]s) of [[zygomycete|zygomycetous]] fungi which are produced by sexual gametocystogamy and can give rise to a conidiophore ("zygosporangium") with asexual conidiospores.
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| − | ===By spore-producing structure===
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| − | In fungi and fungus-like organisms, spores are often classified by the structure in which meiosis and spore production takes place, such as a [[telium]], [[ascus]], [[basidium]], or [[oogonium]], which produce [[teliospore]], [[ascospores]], [[basidiospores]], and [[oospores]], respectively. Since fungi are often classified according to their spore-producing structures, these spores are often characteristic of a particular taxon of the fungi, such as [[Ascomycota]] or [[Basidiomycota]].
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| − | ===By origin during [[Biological life cycle|life cycle]]===
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| − | [[Image:Macrospore-formation.svg|thumb|200px|right|[[Macrospore|Megaspore]] ('''macrospore''') formation in [[plant]]s.]]
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| − | [[Image:Microspore-formation.svg|thumb|200px|right|[[Microspore]] formation in [[plant]]s.]]
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| − | [[Meiospore]]s are the product of [[meiosis]] (the critical cytogenetic stage of [[sex]]ual reproduction), meaning that they are [[haploid]], and will give rise to a haploid daughter cell(s) or a haploid individual. An example is the parent of [[gametophyte]]s of the higher vascular plants ([[Flowering plant|angiosperms]] and [[gymnosperm]]s)—the '''microspores''' (give rise to [[pollen]]) and '''megaspores''' (or '''macrospores''') (give rise to [[ovule]]s) found in [[flower]]s and [[Conifer cone|cones]]; these plants accomplish dispersal by means of [[seed]]s.
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| − | A [[mitospore]] ([[conidium]], conidiospore) is an asexually produced propagule, the result of [[mitosis]]. Mos
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| − | t [[fungi]] produce mitospores. Mitosporic fungi are also known as anamophic fungi (compare [[teleomorph]] or [[deuteromycota|deuteromycetes]]).
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| − | ===By [[motility]]===
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| − | Spores can be differentiated by whether they can move or not. [[Zoospore]] can move by means of one or more [[flagellum]] and can be found in some [[algae]] and [[fungi]]. [[Aplanospore]] cannot move, but may potentially grow flagella. [[Autospore]] cannot move and do not have the potential to ever develop any flagella. [[Ballistospore]] are actively discharged from the body of a fungal fruit (such as a [[mushroom]]). [[Statismospore]] are not actively discharged from the fungal fruit body, similarly to a [[puffball]].
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| − | ==Parlance==
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| − | In common parlance, the difference between "spore" and "[[gamete]]" (both together called [[gonite]]s) is that a spore will germinate and develop into a [[sporeling]], while a gamete needs to combine with another gamete before developing further. However, the terms are somewhat interchangeable when referring to gametes.
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| − | A chief difference between spores and seeds as [[Biological dispersal|dispersal units]] is that spores have very little stored food resources compared with seeds, and thus require more favorable conditions in order to successfully germinate. Spores, therefore, are more resistant to harsh conditions and require less [[energy]] to start [[mitosis]]. Spores are usually produced in large numbers to increase the chance of a spore surviving.
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| − | The [[endospores]] of certain bacteria are often incorrectly called spores, as seen in the [[2001 anthrax attacks]] where ''anthrax endospores'' were incorrectly called ''anthrax spores'' by the media. Several key differences between bacterial endospores and eukaryotic spores exist: they are primarily a survival mechanism, not a reproductive method, and a bacterium only produces a single endospore.
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| − | ==Diaspores==
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| − | In the case of spore-shedding [[vascular plant]]s such as [[fern]]s, wind distribution of very light spores provides great capacity for dispersal. Also, spores are less subject to animal predation than seeds because they contain almost no food reserve; however they are more subject to fungal and bacterial predation. Their chief advantage is that, of all forms of progeny, spores require the least energy and materials to produce.
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| − | Vascular plant spores are always [[haploid]] and vascular plants are either '''''homosporous''''' or '''''heterosporous'''''. Plants that are ''homosporous'' produce spores of the same size and type. ''Heterosporous'' plants, such as [[spikemoss|spikemosses]], [[quillwort]]s, and some aquatic ferns produce spores of two different sizes: the larger spore in effect functioning as a "[[female]]" spore and the smaller functioning as a "[[male]]".
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| − | Under high [[magnification]], spores can be categorized as either '''monolete spores''' or '''trilete spores'''. In monolete spores, there is a single line on the spore indicating the axis on which the mother spore was split into four along a vertical axis. In trilete spores, all four spores share a common origin and are in contact with each other, so when they separate each spore shows three lines radiating from a center pole.
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| − | == See also ==
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| − | *[[Media:Fungus_spore_ejection.ogg|A video of spores being ejected by fungus]]
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| − | *[[Alternation of generations]]
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| − | *[[Sporophyte]]
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| − | *[[Endospore]]
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| − | *[[Fern]]
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| − | *[[Auxillary cell]]
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| − | [[Category:Plant reproduction]] <!--both; until unicellular cat splits off-->
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| − | [[Category:Biological reproduction]]
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| − | [[Category:Germ cells]]
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| − | [[Category:Fungal morphology and anatomy]]
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