Living organisms in any biome interact through a variety of relationships. Organisms compete for food, water, and other resources. Predators hunt their prey. Some organisms coexist in mutually beneficial relationships (symbiosis), while others harm organisms for their own benefit (parasitism). Still others benefit from a relationship that neither helps nor harms the other organism (commensalism).
Animals found in the Arctic tundra include herbivorous mammals (lemmings, voles, caribou, arctic hares, and squirrels), carnivorous mammals (arctic foxes, wolves, and polar bears), fish (cod, flatfish, salmon, and trout), insects (mosquitoes, flies, moths, grasshoppers, and blackflies), and birds (ravens, snow buntings, falcons, loons, sandpipers, terns, and gulls). Reptiles and amphibians are absent because of the extremely cold temperatures. While many of the mammals have adaptations that enable them to survive the long cold winters and to breed and raise young quickly during the short summers, most birds and some mammals migrate south during the winter
A closed system is a system that makes no physical or chemical exchanges with its environment. Of these systems provided as choices (tree, human, clock, car), only a clock does not make exchanges with the environment, except for energy. Therefore, of that list, only a clock would be a closed system. Hope that helped! =)
In an ecosystem, energy is transferred from one organism in a trophic level to another organism in another trophic level. Organisms called PRODUCERS are capable of deriving energy from the sun. However, when fed upon by PRIMARY CONSUMERS, only about 10% of the energy is transferred to them because most of the energy (90%) is lost as heat.
Hence, in this case where the producers had 6,000 kcal of energy, 10% i.e. 10/100 of 6000 = 600 kcal of energy will be transferred to the primary consumers.
