Increаsed blооd levels оf the hormone ADH increаses urine production.
At оne time grаsslаnds cоvered аbоut 42 percent of the land surface of Earth. In the Northern Hemisphere great expanses of grassland covered the midcontinent of North America and extended across the central part of Eurasia. In the Southern Hemisphere grasses covered much of the southern tip of South America and the high plateau of southern Africa. Today grasslands probably occupy less than 12 percent, for most of them have been plowed under for cropland and degraded by overgrazing. Humans have foolishly broken up grasslands with the plow and converted the most productive of them into the breadbaskets of the world. All grasslands have in common a climate characterized by rainfall between 250 and 800 mm (too light to support a heavy forest and too great to result in a desert), a high rate of evaporation, and periodic severe droughts. They share a rolling to flat terrain. Grazing and burrowing species are the dominant animals. Most grasslands require periodic fires for maintenance, renewal, and elimination of woody growth. Grasses have a mode of growth that adapts them to grazing and fire. The grass plant consists of leafy shoots called tillers. Each shoot has a leaf-like blade or lamina, the base of which has a tube-like sheath. These tillers grow from short, underground stems, which grow upward only when the plant begins flowering. Tillers that group closely about a central stem and buds make up a bunch or tussock grasses. Species that spread lateral buds on underground stems, producing a sod, are sod or turf grasses. Associated with grasses are a verity of legumes and composite plants. (Smith, Robert Leo and Thomas M. Smith. 2000. Elements of Ecology, 4th Ed. p. 397) Which sentence best states the main idea of the passage?