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Tundra ecosystems developed in the Northern Hemisphere toward the end of the Pliocene (3.6 ma), prior to this point the Arctic was predominantly covered with forests and shrublands which extended northward to the coastline of the Arctic Ocean. However, during the middle Pleistocene this vegetation pattern shifted to a graminoid tundra steppe. [18]
Plant-animal interactions are important pathways for the transfer of energy within ecosystems, where both advantageous and unfavorable interactions support ecosystem health. [ 1 ] [ 2 ] Plant-animal interactions can take on important ecological functions and manifest in a variety of combinations of favorable and unfavorable associations, for ...
By adapting to these harsh conditions, animals and plants represent iconic characteristics of the tundra. Plants grow in aggregated formations which provide shelter from wind, and ice and also improve seed success. [1] Animals have adapted with specialized organs, such as a rete mirabile, an organ that efficiently transfers heat.
The gallbladder has a capacity of about 50 millilitres (1.8 imperial fluid ounces). [2] The gallbladder is shaped like a pear, with its tip opening into the cystic duct. [4] The gallbladder is divided into three sections: the fundus, body, and neck. The fundus is the rounded base, angled so that it faces the abdominal wall.
The flora of the alpine tundra is characterized by plants that grow close to the ground, including perennial grasses, sedges, forbs, cushion plants, mosses, and lichens. [28] The flora is adapted to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolet radiation, and a short growing season.
Though tundra covers only a minority of the Earth's surface (17-20%), the biodiversity of plant species is important to human nutrition. Of the 20 plant species that make up 80% of human food, 7 of them (35%) originated in this region. [13] Alpine flora at 11,500 feet (3500 m) on the Flat Tops plateau in the Colorado Rocky Mountains U.S.A
The western and eastern Sierra Nevada have substantially different species of plants and animals, because the east lies in the rain shadow of the crest. The plants and animals in the east are thus adapted to much drier conditions. [4] The altitudes listed for the biotic zones are for the central Sierra Nevada.
The mean chain length of an entire web is the arithmetic average of the lengths of all chains in a food web. [42] [14] In a simple predator-prey example, a deer is one step removed from the plants it eats (chain length = 1) and a wolf that eats the deer is two steps removed from the plants (chain length = 2).