University:
Sam Houston State University
Course:
BIOL 1406 | General Biology I
Academic year:

2022
Views:

225

Pages:

12
Author:

Clint W.

NUTRIENT CYCLES NUTRIENT CYCLES: ECOSYSTEM TO ECOSPHERE   Nutrient cycling occurs at the local level through the action of the biota. Nutrient cycling occurs at the global level through geological processes, such as, atmospheric circulation, erosion and weathering. NUTRIENT CYCLES    The atoms of earth and life are the same; they just find themselves in different places at different times. Most of the calcium in your bones came from cows, who got it from corn, which took it from rocks that were once formed in the sea. The path atoms take from the living (biotic) to the non-living (abiotic) world and back again is called a biogeochemical cycle. Nutrients: The Elements of Life   Of the 50 to 70 atoms (elements) that are found in living things, only 15 or so account for the major portion of living biomass. Only around half of these 15 have been studied extensively as they travel through ecosystems or circulate on a global scale. O OXYGEN K POTASSIUM P PHOSPHORUS C CARBON Si SILICON Cl CHLORINE H HYDROGEN Mg MAGNESIUM Fe IRON N NITROGEN S SULFUR Mn MANGANESE Ca CALCIUM Al ALUMINUM Na SODIUM A GENERALIZED MODEL OF NUTRIENT CYCLING IN AN ECOSYSTEM   The cycling of nutrients in an ecosystem are interlinked by an a number of processes that move atoms from and through organisms and to and from the atmosphere, soil and/or rocks, and water. Nutrients can flow between these compartments along a variety of pathways. Nutrient Compartments in a Terrestrial Ecosystem     The organic compartment consists of the living organisms and their detritus. The available-nutrient compartment consists of nutrients held to surface of soil particles or in solution. The third compartment consists of nutrients held in soils or rocks that are unavailable to living organisms. The fourth compartment is the air which can be found in the atmosphere or in the ground. Uptake of Inorganic Nutrients from the Soil   With the exception of CO2 and O2 which enter though leaves, the main path of all other nutrients is from the soil through the roots of producers. Even consumers which find Ca, P, S and other elements in the water they drink, obtain the majority of these nutrients either directly or indirectly from producers.  E.g. you get calcium from milk which came from the diet of the cow – producers. The Atmosphere Is a Source of Inorganic Nutrients    The atmosphere acts as a reservoir for carbon dioxide (CO2), oxygen (O2) and water (H2O). These inorganic compounds can be exchanged directly with the biota through the processes of photosynthesis and respiration. The most abundant gas in the atmosphere is nitrogen (N2);about 80% by volume. Its entry into and exit from the biota is through bacteria. Some Processes By Which Nutrients Are Recycled   Cycling within an ecosystem involves a number of processes. These are best considered by focusing attention on specific nutrients. CARBON, HYDROGEN AND OXYGEN CYCLES IN ECOSYSTEMS     C, H & O basic elements of life; making up from about 98% of plant biomass. CO2 and O2 enter biota from the atmosphere. Producers convert CO2 and H2O into carbohydrates (CH2O compounds) and release O2 from water. Producers, consumers and decomposers convert CH2O compounds, using O2, back into CO2 and H2O. CARBON, HYDROGEN AND OXYGEN CYCLES IN ECOSYSTEMS   Carbon and oxygen cycle come out of the air as carbon dioxide during photosynthesis and are returned during respiration. Oxygen is produced from water during photosynthesis and combines with the hydrogen to form water during respiration. PHOSPHOROUS CYCLE IN ECOSYSTEMS  Phosphorus, as phosphate (PO4-3), is an essential element of life.  It does not cycle through atmosphere, thus enters producers through the soil and is cycled locally through producers, consumers and decomposers.  Generally, small local losses by leaching are balanced by gains from the weathering of rocks.  Over very long time periods (geological time) phosphorus follows a sedimentary cycle.