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Life and Global Chemical Cycles Micronutrients Elements required in small amounts by all life or moderate amounts by some forms of life Macronutrients.

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Presentation on theme: "Life and Global Chemical Cycles Micronutrients Elements required in small amounts by all life or moderate amounts by some forms of life Macronutrients."— Presentation transcript:

1 Life and Global Chemical Cycles Micronutrients Elements required in small amounts by all life or moderate amounts by some forms of life Macronutrients 24 elements required by all organisms Include the “big six,” which are the building blocks of life Carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur Each plays a special role in organisms Copyright © 2014 by John Wiley & Sons, Inc.

2 Life and Global Chemical Cycles For life to persist elements must be available at the right time, in the right amount, and in right concentrations relative to one another Too much of some elements—can be toxic Too little of some elements—can limit growth and development Neutral—some elements are neutral for life Copyright © 2014 by John Wiley & Sons, Inc.

3 General Aspects of Biogeochemical Cycles Some chemicals cycle quickly and are readily regenerated for biological activity They typically have a gas phase, are soluble and carried by the hydrologic cycle Oxygen and nitrogen are examples Other chemical elements are relatively immobile and returned by geological processes Typically lack a gas phase and are insoluble Phosphorus is an example Copyright © 2014 by John Wiley & Sons, Inc.

4 General Aspects of Biogeochemical Cycles Most required nutrients are light Heaviest is iodine with atomic weight of 53 Since life evolved it has altered biogeochemical cycles The continuation of processes that control biogeochemical cycles is essential for maintenance of life Copyright © 2014 by John Wiley & Sons, Inc.

5 General Aspects of Biogeochemical Cycles Through modern technology transfer rate of elements into air, water, and soil have been altered May benefit society, but may also pose environmental hazard Mankind must recognize the + and – consequences of altering cycles Copyright © 2014 by John Wiley & Sons, Inc.

6 General Aspects of Biogeochemical Cycles Simplest way to view a cycle is a box-and- arrow diagram Boxes represent places where a chemical is stored Donating compartment is a source Receiving compartment is a sink Amount of time an atom spends in any compartment is called its residence time Arrows represent pathways of transfer Flow is the amount moving from one box to another Flux is the rate of transfer Copyright © 2014 by John Wiley & Sons, Inc.

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8 The Hydrologic Cycle The transfer of water from oceans to the atmosphere to the land and back to the oceans Driven by solar energy Evaporation of water from oceans Precipitation of water on land Transpiration of water by plants Evaporation of water from land Runoff from streams, rivers and subsurface groundwater Copyright © 2014 by John Wiley & Sons, Inc.

9 The Hydrologic Cycle Total water on earth = 1.3 billion km 3 97% in oceans 2% in glaciers and ice caps 0.76% is shallow groundwater 0.013% in lakes and rivers 0.001% in atmosphere The rest in fresh water on land Copyright © 2014 by John Wiley & Sons, Inc.

10 The Hydrologic Cycle At the regional and local level, the fundamental unit of the landscape is the drainage basin, a.k.a. watershed or catchment The area that contributes surface runoff to a particular stream or river Vary greatly in size Usually named for main stream or river Copyright © 2014 by John Wiley & Sons, Inc.

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12 The Carbon Cycle Carbon is the element that anchors all organic substances Carbon has a gaseous phase Enters atmosphere (CO 2 and CH 4 ) through respiration, fires and diffusion Removed from the atmosphere by photosynthesis Copyright © 2014 by John Wiley & Sons, Inc.

13 The Carbon Cycle Carbon occurs in the ocean in several forms Dissolved CO 2, carbonate and bicarbonate Marine organisms and their products, CaCO 3 Enters the ocean by Simple diffusion then dissolves Transfer from land in rivers as dissolved carbon Wind Copyright © 2014 by John Wiley & Sons, Inc.

14 The Carbon Cycle Carbon enters the biota through photosynthesis and then returned by respiration or fire When organisms die, decomposition of their remains releases carbon If buried under certain conditions, carbon is not released Transformed into fossil fuels Copyright © 2014 by John Wiley & Sons, Inc.

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17 The Carbon-Silicate Cycle The cycling of carbon intimately involved with the cycling of silicon Weak carbonic acid falls as rain and weathers silicate rich rocks Releases Ca 2+ and HCO 3 - Transferred to oceans and used by marine animals to construct shells Shells deposited on sea floor become part of sedimentary rock layer and return to surface in subduction zones Copyright © 2014 by John Wiley & Sons, Inc.

18 The Carbon-Silicate Cycle Affects the levels of CO 2 and O 2 in the atmosphere Copyright © 2014 by John Wiley & Sons, Inc.

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20 The Nitrogen Cycle N essential to life because it is necessary for the production of proteins and DNA Free N 2 makes up 78% of atmosphere But most organisms can’t use it directly Relatively unreactive element must be converted to NO 3 - or NH 4 + Performed by bacteria Copyright © 2014 by John Wiley & Sons, Inc.

21 The Nitrogen Cycle Nitrogen fixation—process of converting atmospheric N to NO 3 - or NH 4 + Denitrification—process of releasing fixed N back to molecular N Almost all organisms depend on nitrogen-converting bacteria Some have formed symbiotic relationships in the roots of plants or stomach in animals Copyright © 2014 by John Wiley & Sons, Inc.

22 The Nitrogen Cycle Industrial process can now convert molecular N into compounds usable by plants Main component of N fertilizers N in agricultural runoff potential source of water pollution N combines with O at high temperatures Oxides of N are a source of air pollution Copyright © 2014 by John Wiley & Sons, Inc.

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24 The Phosphorus Cycle P one of the “big six” required for life Often a limiting factor for plant and algae growth Does not have a gaseous phase Rate of transfer slow Copyright © 2014 by John Wiley & Sons, Inc.

25 The Phosphorus Cycle Enters biota through uptake as phosphate by plants, algae and some bacteria Returns to soil when plants die or is lost to oceans via runoff Returned to land via ocean-feeding birds’ excrement (guano) Guano deposits major source of P for fertilizers [Insert FIGRE 7.21a Guano Island, Peru.] Copyright © 2014 by John Wiley & Sons, Inc.

26 The Phosphorus Cycle Phosphorous mining creates environmental problems Overabundance of phosphorous in runoff causes pollution problems Unwanted growth of photosynthetic bacteria & algae Oceanic dumping of organic materials high in N & P has produced several hundred “dead zones” Copyright © 2014 by John Wiley & Sons, Inc.

27 The Phosphorus Cycle Copyright © 2014 by John Wiley & Sons, Inc.

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29 Chapter Summary Biogeochemical cycles tend to be complex Earth’s biota has greatly altered the cycling of chemicals through the air, water, and soil Continuation of these processes is essential to the long-term maintenance of life on Earth Copyright © 2014 by John Wiley & Sons, Inc.

30 Chapter Summary There are many uncertainties In measuring the amount of a chemical in storage In determining the rate of its transfer between reservoirs Understanding biogeochemical cycles more completely will help us more fully understand our environment and how to properly manage its resources for now and the future Copyright © 2014 by John Wiley & Sons, Inc.


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