Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability. These areas tend to fall upon degraded soils, and their health and functioning are key necessities of regulating ecosystems’ atmospheric components.
A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-arid climates, depending on variables such as temperature, and they give rise to different biomes.
An aridity index (AI) is a numerical indicator of the degree of dryness of the climate at a given location. The American Meteorological Society defined it in meteorology and climatology, as "the degree to which a climate lacks effective, life-promoting moisture". Aridity is different from drought because aridity is permanent whereas drought is temporary. A number of aridity indices have been proposed (see below); these indicators serve to identify, locate or delimit regions that suffer from a deficit of available water, a condition that can severely affect the effective use of the land for such activities as agriculture or stock-farming.
MultiCam is a camouflage pattern designed for use in a wide range of environments and conditions which was developed and is produced by American company Crye Precision. The pattern has found extensive adoption globally. Variants of it, some unlicensed, are in use with militaries worldwide, particularly with special forces/special operations forces units.
The pattern is also available for purchase for civilian usage. Derived from the original standard pattern, additional specified variants were developed and later introduced in late 2013, those are "Arid", "Tropic", "Alpine" and "Black".
The mammalian kidneys are a pair of excretory organs of the urinary system of mammals, being functioning kidneys in postnatal-to-adult individuals (i. e. metanephric kidneys). The kidneys in mammals are usually bean-shaped or externally lobulated. They are located behind the peritoneum (retroperitoneally) on the back (dorsal) wall of the body. The typical mammalian kidney consists of a renal capsule, a peripheral cortex, an internal medulla, one or more renal calyces, and a renal pelvis. Although the calyces or renal pelvis may be absent in some species. The medulla is made up of one or more renal pyramids, forming papillae with their innermost parts. Generally, urine produced by the cortex and medulla drains from the papillae into the calyces, and then into the renal pelvis, from which urine exits the kidney through the ureter. Nitrogen-containing waste products are excreted by the kidneys in mammals mainly in the form of urea.
The structure of the kidney differs between species. The kidneys can be unilobar (a single lobe represented by a single renal pyramid) or multilobar, unipapillary (a single or a common papilla), with several papillae or multipapillary, may be smooth-surfaced or lobulated. The multilobar kidneys can also be reniculate, which are found mainly in marine mammals. The unipapillary kidney with a single renal pyramid is the simplest type of kidney in mammals, from which the more structurally complex kidneys are believed to have evolved. Differences in kidney structure are the result of adaptations during evolution to variations in body mass and habitats (in particular, aridity) between species.