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	Trophic levels
		Trophic levels are the feeding position in a food chain such as primary producers, herbivore, primary carnivore, etc. Green plants form the first trophic level, the producers.
		Trophic levels and the energy flow from one level to the next, can be graphically depicted using an ecological pyramid.
		An energy pyramid shows clearly that the energy transfer from one trophic level to the next is accompanied by a decrease due to waste and the conversion of potential energy into kinetic energy and heat energy.
	www.botany.uwc.ac.za /sci_ed/grade10/ecology/trophics/troph.htm (546 words)

	[No title]
		Trophic levels are abstractions which group together all species in a food web that occupy the same position in the food chain.
		Trophic level analysis provides an opportunity to compare different communities because this type of analysis is free of the specific differences in species composition and vegetation type, e.
		Comparison of trophic levels: pyramid of numbers One of the first attempts to analyze trophic relationships and arrive at a generalized picture of community structure involved relating the different trophic levels to the number of individuals found in each level.
	www.holycross.edu /departments/biology/whealy/notes_text/bt.text (1978 words)

	Trophic level - Wikipedia, the free encyclopedia
		This is why trophic levels are usually portrayed as a triangle, one that places grass on the bottom and mountain lions on top---the top is always much smaller than the bottom.
		In the ocean, phytoplankton is the primary producer (the first level in the food chain or the first trophic level).Phytoplankton converts inorganic carbon into protoplasm.
		A compelling sidenote to the discussion of trophic levels is the incongruence of low-level trophic efficiency and the upward trophic movement of species described in evolutionary theory.
	en.wikipedia.org /wiki/Trophic_level (1118 words)

	The Daily Star Web Edition Vol. 4 Num 170 (Site not responding. Last check: 2007-10-12)
		Trophic level is the position of an organism in the food chain, determined by the number of transfers of energy that occur between the non-living energy source and that position.
		Among these, all plants belong to trophic level 1 and other trophic levels (2-4 or 5) are functioned with the animals as the members of the ecosystem.
		In the figure trophic level 3 has been marked with 3+x, because a member of trophic level 3 may become the member of trophic level 2 (when feeds on plants) at the same time when feeds on other phytophagous animals or carnivorous animals then it could be of trophic level 4 or 5.
	www.thedailystar.net /2003/11/14/d31114180197.htm (1864 words)

	Glossary: Trophic level
		A trophic level of an organism is its position in a food chain.
		Levels are numbered according to how far particular organisms are along the chain from the primary producers [plants] at level 1, to herbivores (level 2), to predators (level 3), to carnivores or top carnivores (level 4 or 5).
		Fish at higher trophic levels are typically of higher economic value.
	www.greenfacts.org /glossary/tuv/trophic-level.htm (101 words)

	Trophic Levels
		The term trophic level originally came from ecology, denoting the position in the food chain, as determined by the number of energy-transfer steps to that level.
		The simplest forms of social trophic levels are in economy, where it denotes the distance from direct physical sustenance.
		The maximum number of trophic levels depends on factors of available technology (the number needs to increase if it is highly specialised and many middle-men needed to combine it, while general assembly lowers it) and information processing (the available information processing limits the efficiency and manageability of economic interactions, limiting the maximum number of levels).
	www.orionsarm.com /civ/trophic_levels.html (527 words)

	Fishing down aquatic food webs
		Fish that normally consume zooplankton were assigned a trophic level of three, because zooplankton (with a trophic level of two) normally consume phytoplankton (trophic level of one).
		In the northwest Atlantic, for example, trophic level plunged from a peak of nearly 3.7 in 1965 to 2.8 in 1997 (the last year for which statistics are available), while in the northeast Atlantic it fell from about 3.6 to 3.4.
		Maybe the shift toward lower values of average trophic level simply reflects an increase in number of plankton feeders in many places, perhaps species that are now thriving from the coastal plankton blooms that take place when fertilizer leached from farmers' fields is carried to the ocean by rivers and streams.
	www.seafriends.org.nz /issues/fishing/pauly0.htm (3774 words)

	GEO Year Book 2003
		Levels are numbered according to how far particular organisms are along the chain from the primary producers at level 1, to the top predators at the highest level.
		Within marine systems, large predators such as sharks and saithe, are at a high trophic level, cod and sardines are in the middle, and shrimp are at a low trophic level with microscopic plants (mainly phytoplankton) at the bottom sustaining marine life.
		Monitoring the average trophic level of fish catches can show when stocks of larger predatory fish are beginning to collapse.
	www.unep.org /GEO/yearbook/yb2003/098.htm (507 words)

	9. TROPHIC LEVEL EFFICIENCY AND THE THIRD TROPHIC LEVEL
		It should be pointed out that the higher value of trophic level efficiency is derived in the simpler way by merely taking the number of generations and not the lengthened generations.
		The production at the third trophic level may be estimated by taking 1 per cent of the primary production or 10 per cent of the secondary production by both of the estimates used.
		To account for part of the invertebrate third trophic level, 9 per cent of the secondary production is taken, and the tertiary production would then amount to about 120 M tons or ca 210 M tons at a 15 per cent conversion rate.
	www.fao.org /docrep/89204e/89204e0a.htm (1346 words)

	Trophic Pyramids
		The descriptive device used to explore this facet of the trophic structure of an ecosystem is called a trophic pyramid.
		The purpose of a trophic pyramid is to graphically represent the distribution of biomass or energy among the different trophic levels of the ecosystem.
		The tertiary consumer level is much smaller still, etc. This relative size relationship exists in both bioimass and energy trophic pyramids, but it is much more exaggerated in energy pyramids than biomass pyramids.
	www.cod.edu /people/faculty/fancher/TrophicPyramids.htm (634 words)

	Chapter 54 Student Interactive Guide
		Food chain is the pathway along which food is transferred from trophic level to trophic level, beginning with primary producers.
		The transfer of energy from one trophic level to another is not 100%.
		The amount of energy available to each trophic level is determined by NPP and the efficiencies with which food energy is converted to biomass in each link of the food chain.
	www.niles-hs.k12.il.us /jacnau/chpt54.html (6156 words)

	How Pervasive is "Fishing Down Marine Food Webs"? -- Caddy et al. 282 (5393): 1383 -- Science
		Trophic level trends (A) in Cuban landings from the Western Central Atlantic (FAO area 31, 1966 to 1996) and in Gulf of Thailand trawl survey data, 1966 to 1982 (4); (B) in global marine fisheries, 1984 to 1996 (from FAO landings, also shown), after removal of mariculture production data.
		It is based on 39 highly aggregated trophic level estimates from an earlier contribution of D. Pauly and V. Christensen [Nature 374, 255 (1995)], rather than on the more than 200 estimates of trophic level we used for our report (1) and made available through www.fishbase.org.
		Further, it suggests trophic level values for aquaculture as a whole to be increasing from 1.55 in 1984 to about 1.7 to 1.8 in the 1990s.
	www.sciencemag.org /cgi/content/full/282/5393/1383a (2800 words)

	Zooplankton
		The efficiency with which the biomass of one trophic level is transferred to the biomass of the next trophic level is known as the transfer efficiency.
		This means that for each successive trophic level, there is an 80 to 90% energy loss through respiration and motion.
		Lower population numbers suggest lower total mass (standing stock) for higher trophic levels, but due to their larger size and longer generation times, standing stocks of trophic levels in a food chain remain fairly constant, within an order of magnitude.
	www-ocean.tamu.edu /~wormuth/zooplankton.html (659 words)

	Trophic Dynamics (Site not responding. Last check: 2007-10-12)
		Trophic cascade models suggest that interactions can flow up or down the trophic structure and that organisms on any level can have dramatic effects on the composition of the community.
		Fourth trophic level - a specialist predatory beetle Tarsobaenus letourneauae, whose larvae live in the hollow petioles and kill adult ants and ant broods.
		Letourneau and Dyer conducted a manipulative experiment in which levels of top-predatory were altered and effects on successive lower trophic levels were monitored.
	www.utoronto.ca /env/jah/C61_lc78.htm (3394 words)

	Food Web - MSN Encarta
		Secondary carnivores, which are predators that feed on predators, belong to the fourth trophic level.
		At the second and higher levels, decomposers of the available materials function as herbivores or carnivores depending on whether their food is plant or animal material.
		Most of the energy assimilated at the second trophic level is again lost as heat in respiration; a fraction becomes new biomass.
	encarta.msn.com /encyclopedia_761557485/Food_Web.html (530 words)

	Trophic Level Index
		The Trophic Level Index (TLI) is an indicator of lake water quality.
		High levels of water-bound nitrogen and phosphorus most often come from agricultural runoff and urban wastewater, but can also come from geothermal inputs and deep springs that leach phosphorus from the rock geology.
		Trophic level bands are grouped into trophic states for quantitative description, microtrophic to hypertrophic as shown below.
	www.envbop.govt.nz /water/lakes/trophic-level-index.asp (722 words)

	pmcHT
		The presentations on higher trophic levels components were mixed; some were reviews of past studies in Florida Bay, some were proposed studies/models to be done in Florida Bay, and some were reviews of studies (or models) conducted elsewhere that might have applicability to Florida Bay.
		The development of the research plan for higher trophic levels seems to be more a reaction to reviews by the oversight panel and less pro-active consideration of important elements based on a strong conceptual model.
		Until a comprehensive conceptual model is developed, and funding for key elements is secure, the higher trophic level work will continue to be an eclectic collection that reflects the 'art of the possible', rather than what is truly needed to address the issue at hand.
	www.aoml.noaa.gov /flbay/pmcht.html (5178 words)

	Quick Draw - Habitats - Elementary Teachers - Curriculum Guide and On-line Activities - Great Sand Dunes National Park ...
		Trophic levels are simply a way for ecologists to describe the food chain.
		It is important to note that trophic levels are visualized as pyramidal in shape.
		Because energy is lost in the form of heat at each level, the quantity of life that can be supported becomes smaller at each level.
	www.nps.gov /archive/grsa/resources/curriculum/elem/lesson37.htm (744 words)

	lect25
		Trophic Level: Every level in the food production or consumption in the food chain or food web is called a trophic level.
		The higher up the trophic level the less energy is present.
		Only 5-20% of energy is passed from one trophic level to the next.
	www.gpc.edu /~pahanotu/lect25.htm (1263 words)

	A World of Diversity
		The first trophic level is the primary consumers or herbivores, these animals only eat living plants, and the primary consumers are eaten by the secondary consumers, which are the carnivores and parasites.
		The suns energy is essential to all life in an ecosystem and is harnessed by the photosynthetic organisms, which are then eaten by the primary consumers and secondary consumers which are decomposed by the decomposers.
		At each trophic interaction energy is lost, usually in the form of heat, this energy is then radiated back into space.
	library.thinkquest.org /C007506/trophic.html (255 words)

	Ecorisk Fundamentals: 1.4 Trophic Levels and Food Webs
		The trophic level designation for a carnivore is determined by the trophic level of the animal it eats.
		This figure also identifies trophic levels for the types of organisms indicated, although many of the organisms could be identified as belonging to more than one trophic level.
		An important aspect of the transfer of organic matter and energy from one trophic level to the next is the loss of energy during each transfer.
	web.ead.anl.gov /ecorisk/fundamentals/html/ch1/1.4.htm (802 words)

	Amazon Life - Ecology - Energy Flow
		The fourth trophic level is constituted by tertiary consumers, that is, carnivorous that feed on carnivorous.
		The sequence of trophic levels represents the path in which energy is transferred in an ecosystem.
		In each trophic level energy is used in various activities and is dissipated in heat form.
	library.thinkquest.org /20248/fe.html (901 words)

	Fish culture in undrainable ponds A manual for extension
		At times the pondwater is supersaturated with oxygen during the day, which is a highly unstable state, while during the night, a greater proportion of oxygen is used up for their respiration, thereby reducing the availability of oxygen to fish.
		Since considerable amount of energy is lost in successive trophic levels of the food chain, efficient fish culture always aims at making the chain as short as possible.
		Proper stocking rate for a pond is that optimum level which results in a given time, usually a year, in a production which is highest in quantity and quality of fish, and most profitable.
	www.fao.org /docrep/003/T0555E/T0555E02.htm (2891 words)

	Trophic level (Site not responding. Last check: 2007-10-12)
		This means so many units of grass can only support a much smaller number of units of rabbits, who can only support a smaller group of bobcats, who can only support a smaller group of cougars.
		This is why trophic levels are usually portrayed as a triangle, one that places grass on the bottom and cougars on top---the top is always much smaller than the bottom." Each level implies a loss of Energy and efficiency and less life that can be supported by the sun.
		Producers (autotrophs) utilise Energy from the sun and nutrients from the abiotic environment (carbon dioxide from the air or water, other nutrients from the soil or water) to perform photosynthesis and grow.
	trophic-level.iqnaut.net (798 words)

	Botany online: Ecosystems - Flow of Energy in Ecosystems - Productivity, Food Chain, Trophic Level
		As was explained in the last subchapter, the flow of energy is an essential feature of every ecosystem, since all living systems are open systems.
		The amount of biomass decreases drastically from one trophic level to the next one as the flow of energy is a directed process and as an optimal ten percent of the biomass of the previous tropic level can be used in the next higher one.
		A theoretically optimal 80 percent of this energy can be used by the organisms of the next higher trophic level.
	www.biologie.uni-hamburg.de /b-online/e54/54c.htm (1452 words)

	Energy Lecture
		trophic level (different from glossary): the order in which organisms receive solar energy.
		Parasitic plants are on the second trophic level.
		Ecological or food chain efficiency: The proportion of productivity in one trophic level which is actually converted into productivity at the next tropic level.
	www.okstate.edu /artsci/botany/bisc3034/lnotes/energy.htm (586 words)

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