Pedogenesis - Organisms

Organisms

The organisms living in and on the soil form distinct soil types. Coniferous forests have acidic leaf litter and form what are known as inceptisols. Mixed or deciduous forests leave a larger layer of humus, changing the elements leeched and accumulated in the soil, forming alfisols. Prairies have very high humus accumulation, creating a dark, thick A horizon characteristic of mollisols.

For example three species of land snails in the genus Euchondrus in the Negev desert are noted for eating lichens growing under the surface limestone rocks and slabs (endolithic lichens). They disrupt and eat the limestone. Their grazing resulting in the weathering of the stones, and the subsequent formation of soil. They have a significant effect on the region: the total population of snails is estimated to process between 0.7 and 1.1 metric ton per hectare per year of limestone in the Negev desert.

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Phylogenetic Nomenclature - Definitions
... the meaning of the name is fixed the ancestor and all organisms which are its descendants are included in the named taxon ... Listing all these organisms (i.e ... Different hypotheses lead to different organisms being thought to be included in the named taxon, but do not affect what organisms the name actually applies to ...

Famous quotes containing the word organisms:

    The white man regards the universe as a gigantic machine hurtling through time and space to its final destruction: individuals in it are but tiny organisms with private lives that lead to private deaths: personal power, success and fame are the absolute measures of values, the things to live for. This outlook on life divides the universe into a host of individual little entities which cannot help being in constant conflict thereby hastening the approach of the hour of their final destruction.
    Policy statement, 1944, of the Youth League of the African National Congress. pt. 2, ch. 4, Fatima Meer, Higher than Hope (1988)