User:Allisonk444/Spore

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In biology, a spore is a unit of sexual (in fungi) 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.

Classification of Spores

Spores can be classified in several ways such as by their spore producing structure, function, origin during life cycle, and mobility.

Below is a table listing the mode of classification, name, identifying characteristic, examples, and images of different spore species.

Mode of Classification	Name		Identifiying Characteristic	Example Spore Containing Organism	Image
Spore Producing Structure	Sporangiospore		Produced by sporangium	Zygomycetes	Sporangium of Fungi
	Zygospores		Produced by zygosporangium	Zygomycetes	Zygospores on Rhizopus
	Ascospores		Produced by ascus	Ascomycetes	Ascospores of Didymella Rabiei
	Basidiospores		Produced by basidium	Basidiomycetes	Typical reproductive structure of a basidiomycete, including the basidiospore and basidium
	Aecispores		Produced by aecium	Rusts and Smuts	Aceium on foilage
	Urediniospores		Produced by uredinium	Rusts and Smuts	Uredinospores
	Teliospores		Produced by teilum	Rusts and Smuts	Microscopic image of teliospores
	Oospores		Produced by oogonium	Oomycetes	Oospores of Phytophthora agathidicida
	Carpospores		Produced by carposophorophyte	Red Algae	Light microscopy of Polysiphonia showing a carpospores and carposporophyte inside
	Tetraspores		Produced by tetrasphorophyte	Red Algae	Tetraspores of Polysiphonia
Function	Chalmydospore		Thick-walled resting spores of fungi produced to survive in unfavorable conditions	Asomycota	Pseudohyphae, chlamydospores and blastospores of Candida yeast.
	Parasitic Fungal Spore	Internal Spores	Germinate within a host		A parasitic pink fungi on a Lichen tree
		External (Environmental) spores	Spores released by the host to infest other hosts
Origin During Life Cycle	Meiospores	Microspores	Produced sexually through meiosis, and give rise to a male gametophyte	Pollen in seed plants	In plants, microspores, and in some cases megaspores, are formed from all four products of meiosis.
		Megaspores (macrospores)	Produced sexually through meiosis, and give rise to a female gametophyte	Ovule in seed plants	In contrast, in many seed plants and heterosporous ferns, only a single product of meiosis will become a megaspore (macrospore), with the rest degenerating.
	Mitospores		Produced asexually though mitosis	Ascomycetes	Ascomycete containing mitospores
Mobility	Zoospores		Mobile through flagella	Some algae and fungi	Microscopic image of a Zoospore
	Aplanospores		Immobile, however still produce flagella
	Autospores		Immobile spores that do not produce flagella		Autospores of a strain of Jenufa aeroterrestrica
	Ballistospores		Forcibly discharged from the fungal fruiting body due to internal force (such as built up pressure)	Basidiospores and/or part of the genus Pilobus	Ballistospore mechanism of dispersal from fungi
	Stratismospores		Forcibly discharged from the fungal fruting body due to external force (such as raindrops or passing animals)	Puffballs	Puff Balls containing Stratismospores

External Anatomy

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Under high magnification, spores often have complex patterns or ornamentation on their exterior surfaces. A specialized terminology has been developed to describe features of such patterns. Some markings represent apertures, places where the tough outer coat of the spore can be penetrated when germination occurs. Spores can be categorized based on the position and number of these markings and apertures. Alete spores show no lines. In monolete spores, there is a single narrow line (laesura) on the spore. Indicating the prior contact of two spores that eventually separated. In trilete spores, each spore shows three narrow lines radiating from a center pole. This shows that four spores shared a common origin and were initially in contact with each other forming a tetrahedron. A wider aperture in the shape of a groove may be termed a colpus. The number of colpi distinguishes major groups of plants. Eudicots have tricolpate spores (i.e. spores with three colpi).

Origin

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Spores have been found in microfossils dating back to the mid-late Ordovician period. Two hypothesized initial functions of spores relate to whether they appeared before or after land plants. The heavily studied hypothesis is that spores were an adaptation of early land plant species, such as embryophytes, that allowed for plants to easily disperse while adapting to their non-aquatic environment. This is particularly supported by the observation of a thick spore wall in cryptospores. These spore walls would have protected potential offspring from novel weather elements. The second more recent hypothesis is that spores were an early predecessor of land plants and formed during errors in the meiosis of algae, a hypothesized early ancestor of land plants.

Whether spores arose before or after land plants, their contributions to topics in fields like paleontology and plant phylogenetics have been useful . The spores found in microfossils, also known as cryptospores, are well preserved due to the fixed material they are in as well as how abundant and widespread they were during their respective time periods. These microfossils are especially helpful when studying the early periods of earth as macrofossils such as plants are not common nor well preserved. Both cryptospores and modern spores have diverse morphology that indicate possible environmental conditions of earlier periods of Earth and evolutionary relationships of plant species.