central case study: vanishing oysters of matter, … 02, 2012 · matter, energy, and ecosystems ......

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© 2012 Pearson Education, Inc.

Chapter 2 - Environmental Systems:Matter, Energy, and Ecosystems• Environmental systems• Environmental chemistry• The molecular building blocks of organisms• Energy and energy flow• Photosynthesis and

respiration• Ecosystems and interactions• Fundamentals of

landscape ecology• Ecosystem services• Carbon, phosphorus, nitrogen, and water cycles


Central Case Study: Vanishing Oysters ofthe Chesapeake Bay

• Chesapeake Bay was theworld’s largest oysterfishery

• Overharvesting, pollution,and habitat destructionruined it

• The economy lost $4billion from 1980 to 2010

• Strict pollution standardsand oyster restorationefforts give reason for hope


The Earth’s systems

• Understanding human impacts on the environmentrequires understanding complex environmental systems– Many issues are multifaceted and interconnected

• System: a network of relationships among componentsthat interact with and influence one another– Exchange of energy, matter, or information– Receives inputs of energy, matter, or information;

processes these inputs; and produces outputs• Feedback loop: a circular process in which a system’s

output serves as input to that same system


Negative feedback loop

• Negative feedback loop: output resulting from a systemmoving in one direction acts as an input that moves thesystem in the other direction– Input and output neutralize one another– Stabilizes the system

• Example: if we get hot, we sweat and cool down• Most systems in nature involve negative feedback loops

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Positive feedback loop• Positive feedback loop: instead of stabilizing a system, it drives

it further toward an extreme• Example: white glaciers reflect sunlight and keep surfaces cool

– Melting ice exposes dark soil, which absorbs sunlight– Causes further warming and melting of more ice

• Runaway cycles of positive feedback are rare in nature– But are common in natural systems altered by humans


Environmental systems interact

• Natural systems are divided into structural spheres• Lithosphere: rock and sediment• Atmosphere: the air surrounding the planet• Hydrosphere: all water on Earth• Biosphere: the planet’s living organisms

– Plus the abiotic (nonliving) parts they interact with• Categorizing systems allows humans to understand

Earth’s complexity– Most systems overlap


The Chesapeake Bay: a systems perspective

• The Chesapeake Bay and rivers that empty into it are aninteracting system:– It receives very high levels of nitrogen and phosphorus from

agriculture from 6 states, and air pollution from 15 states© 2012 Pearson Education, Inc.

Sources of nitrogen and phosphorusentering the Chesapeake Bay

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Eutrophication in the Chesapeake Bay

• Nitrogen and phosphorus enter the Chesapeakewatershed (the land area that drains water into a river),causing….

• Phytoplankton (microscopic algae and bacteria) to grow,then…

• Bacteria eat dead phytoplankton and wastes and depleteoxygen, causing…

• Fish and other aquatic organisms to flee or suffocate• Eutrophication: the process of nutrient overenrichment,

blooms of algae, increased production of organic matter,and ecosystem degradation


Eutrophication in aquatic systems


Global hypoxic dead zones

Nutrient pollution from farms, cities, and industries has ledto more than 400 hypoxic (oxygen-depleted) dead zones


People are changing the chemistry ofEarth’s systems

• Chemistry is crucial for understanding how:– Chemicals affect the health of wildlife and people– Pollutants cause acid precipitation– Synthetic chemicals thin the ozone layer– How gases contribute to global climate change

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Matter

• Matter: all material in the universe that has mass andoccupies space– It can be solid, liquid, or gas

• Law of conservation of matter: matter can betransformed from one type of substance into others– But it cannot be destroyed or created

• Because the amount of matter stays constant– It is recycled in nutrient cycles and ecosystems– We cannot simply wish pollution and waste away


Elements

• Element: a fundamental type of matter– A chemical substance with a given set of properties– Examples: nitrogen, phosphorus, oxygen– 92 natural and 20 artificially created elements exist

• Nutrients: elements needed in large amounts byorganisms– Examples: carbon, nitrogen, calcium


Atoms

• Atoms: the smallest components that maintain anelement’s chemical properties

• The atom’s nucleus (center) has protons (positivelycharged particles) and neutrons (lacking electric charge)– Atomic number: the number of protons

• Electrons: negatively charged particles surrounding thenucleus– Balance the protons’ positive charge


The structure of an atom

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Isotopes and ions

• Isotopes: atoms of an element with differentnumbers of neutrons

• Mass number: the number of protons + neutrons• Isotopes of an element behave

slightly differently• Ions: atoms that gain

or lose electrons– They are electrically

charged


Some isotopes are radioactive and decay

• Radioactive isotopes shed subatomic particles and emithigh-energy radiation– They decay until they become nonradioactive stable

isotopes• Half-life: the amount of time it takes for one-half of the

atoms in a radioisotope to give off radiation and decay– Different radioisotopes have different half-lives ranging

from fractions of a second to billions of years– Uranium-235, used in commercial nuclear power, has a

half-life of 700 million years


Molecules and compounds

• An attraction for each other’s electrons bonds atoms• Molecules: combinations of two or more atoms• Chemical formula: indicates the type and number of

atoms in the molecule (oxygen gas: O2)• Compound: a molecule composed of atoms of two or

more different elements– Water: two hydrogen atoms bonded to one oxygen atom:

H2O– Carbon dioxide: one carbon atom with two oxygen atoms:

CO2


Atoms are held together with bonds

• Ionic bonds: ions of different charges bind together– Table salt (NaCl): the Na+ ion is bound to the Cl– ion

• Covalent bond: atoms without electrical charges“share” electrons– Example: hydrogen atoms share electrons – H2

• Solutions: electrons, molecules and compounds cometogether with no chemical bonding– Air contains O2, N2, H2O, CO2, methane (CH4), ozone

(O3)– Human blood, ocean water, plant sap, metal alloys

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Ionic bonds

Animation: Ionic BondsRight-click / Select “Play” © 2012 Pearson Education, Inc.

Covalent bonds

Animation: Covalent BondsRight-click / Select “Play”


Hydrogen ions determine acidity

• Water can split into H+ and OH–

• The pH scale quantifies theacidity or basicity of solutions

• Acidic solutions: pH < 7– Contain more H+

• Basic solutions: pH > 7– Contain more OH–

• Neutral solutions: pH: 7• A pH of 6 contains 10 times

as many H+ as a pH of 7


Matter is composed of compounds

• Living things depend on organic compounds• Organic compounds: carbon atoms bonded together

– They may include other elements: nitrogen, oxygen,sulfur, and phosphorus

• Carbon can be linked in elaborate chains, rings, otherstructures– Forming millions of different organic compounds

• Inorganic compounds: lack the carbon–carbon bond

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Carbon skeletons

Animation: Carbon SkeletonsRight-click / Select “Play” © 2012 Pearson Education, Inc.

Polysaccharides

Animation: PolysaccharidesRight-click / Select “Play”


Hydrocarbons

• Hydrocarbons: organic compounds that contain onlycarbon and hydrogen– The simplest hydrocarbon is methane (natural gas)

• Fossil fuels consist of hydrocarbons– Crude oil contains hundreds of types of hydrocarbons


Macromolecules are building blocks of life

• Polymers: long chains of repeated organic compounds– Play key roles as building blocks of life

• Three essential types of polymers:– Proteins– Nucleic acids– Carbohydrates

• Lipids are not polymers, but are also essential– Fats, oils, phospholipids, waxes, steroids

• Macromolecules: large-sized molecules essential to life

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Proteins are long chains of amino acids

• Proteins comprise most of an organism’s matter• They produce tissues, provide structural support,

store energy, transport material• Animals use proteins to generate skin, hair, muscles,

and tendons• Some are components of the immune system or

hormones (chemical messengers)• They can serve as enzymes: molecules that promote

(catalyze) chemical reactions


Nucleic acids direct protein production

• Deoxyribonucleic acid (DNA) and ribonucleicacid (RNA) carry hereditary information oforganisms

• Nucleic acids: longchains of nucleotides thatcontain sugar, phosphate,and a nitrogen base

• Genes: regions of DNAthat code for proteins thatperform certain functions


Carbohydrates and lipids

• Carbohydrates: include simple sugars and largemolecules of simple sugars bonded together

• Glucose fuels cells and builds complex carbohydrates• Plants store energy in starch, a complex carbohydrate

– Animals eat plants to get starch• Organisms build structures from complex carbohydrates

– Chitin forms shells of insects and crustaceans– Cellulose found in cell walls of plants

• Lipids do not dissolve in water– Fats and oils (energy), waxes (structure), steroids


Cells compartmentalize macromolecules

• All living things are composed of cells: the most basicunit of organismal organization

• Cells vary in size, shape, and function– They are classified according to their structure

• Eukaryotes: plants, animals, fungi, protists– Contain a membrane-enclosed nucleus– Their membrane-enclosed organelles do specific things

• Prokaryotes: bacteria and archaea– Single-celled, lacking membrane-enclosed nucleus and

organelles

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Energy fundamentals

• Energy: an intangible phenomenon that can change theposition, physical composition, temperature of matter– Involved in biological, chemical, physical processes

• Potential energy: energy of position• Kinetic energy: energy of motion• Chemical energy: potential energy held in the bonds

between atoms• Changing potential into kinetic energy

– Releases energy– Produces motion, action, or heat


Potential vs. kinetic energy

Potential energy stored in our food becomes kineticenergy when we exercise and releases carbon dioxide,water, and heat as by-products

Insert Figure 2.11


Energy is conserved but changes in quality

• First law of thermodynamics: energy can changeform but cannot be created or destroyed

• Second law of thermodynamics: energy changesfrom a more-ordered to a less-ordered state– Entropy: an increasing state of disorder

• Living organisms resist entropy by getting energyfrom food and photosynthesis– Dead organisms get no energy and through

decomposition lose their organized structure


The sun’s energy powers living systems

• Energy that powers Earth’s ecological systems comesmainly from the sun

• The sun releases radiation from the electromagneticspectrum– Some is visible light

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Using solar radiation to produce food

• Autotrophs (producers):organisms that use the sun’senergy to produce their ownfood– Plants, algae, cyanobacteria

• Photosynthesis: the processof turning the sun’s lightenergy into high-qualitychemical energy– Sunlight converts carbon

dioxide and water into sugars


6CO2 + 6H2O + sun’s energy C6H12O6 (sugar) + 6O2

Photosynthesis produces food

• Chloroplasts: organelles where photosynthesis occurs– Contain chlorophyll: a light-absorbing pigment– Light reaction: solar energy splits water and creates high-

energy molecules that fuel the …– Calvin cycle: links carbon atoms from carbon dioxide into

sugar (glucose)


Cellular respiration releases energy

• It occurs in all living things (plants, animals, etc.)• Organisms use chemical energy created by photosynthesis

– Oxygen breaks the high-energy chemical glucose bonds– The energy is used to make other chemical bonds or tasks

• Heterotrophs: organisms that gain energy by feeding onothers– Animals, fungi, microbes– The energy is used for cellular tasks

C6H12O6 (sugar) + 6O2 6CO2 + 6H2O + energy


Ecosystems

• Ecosystem: all organisms and nonliving entities occurringand interacting in a particular area– Animals, plants, water, soil, nutrients, etc.

• Biological entities are tightly intertwined with the chemicaland physical aspects of their environment

• For example, in the Chesapeake Bay estuary (a waterbody where fresh river water flows into salt ocean water):– Organisms are affected by water, sediment, and nutrients

from the water and land– The chemical composition of the water is affected by

organism photosynthesis, respiration, and decomposition

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Energy and matter flow through ecosystems

• Sun energy flows in onedirection through ecosystems

– Energy is processed andtransformed

• Matter is recycled withinecosystems

– Outputs: heat, water flow,and waste


Energy is converted to biomass

• Primary production: conversion of solar energy tochemical energy in sugars by autotrophs duringphotosynthesis

• Gross primary production: total amount of chemicalenergy produced by autotrophs– Most energy is used to power their own metabolism

• Net primary production: energy remaining afterrespiration– Equals gross primary production – cellular respiration– It is used to generate biomass (leaves, stems, roots)– Available for heterotrophs


Primary productivity of ecosystems

• Productivity: rate atwhich autotrophsconvert energy tobiomass

• High net primaryproductivity:ecosystems whoseplants rapidlyconvert solarenergy to biomass


A global map of net primary productivity

NPP increases with temperature and precipitation on land,and with light and nutrients in aquatic ecosystems

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Ecosystems interact across landscapes

• Ecosystems vary greatly in size (puddle, forest, bay, etc.)• The term ecosystem is most often applied to self-

contained systems of moderate geographic extent– Adjacent ecosystems may interact extensively– Ecotones: transitional zones between two ecosystems in

which elements of each ecosystem mix• It may help to view ecosystems on a larger geographic

scale– Encompassing multiple ecosystems– Geographic information systems (GIS) use computer

software to layer multiple types of data together


• Landscape ecology: the study of how landscape structureaffects the abundance, distribution, and interaction oforganisms– Useful for studying migrating birds, fish, mammals– Helpful for planning sustainable regional development

• Patches: ecosystems, communities or habitat formthe landscape and are distributed in complexpatterns (a mosaic)

Landscape ecology

This landscapeconsists of a mosaicof patches of 5ecosystems


Conservation biology

• Conservation biologists: study the loss, protection, andrestoration of biodiversity– Humans are dividing habitat into small, isolated patches– Corridors of habitat can link patches

• Populations of organisms have specific habitatrequirements– They occupy suitable patches of habitat in the landscape

• If a habitat is highly fragmented and isolated– Organisms in patches may perish

• Conservation biologists may use corridors of habitat tolink patches to preserve biodiversity


Modeling helps us understand ecosystems

• Model: a simplified representation of a complicatednatural process– Helps us understand processes and make predictions

• Ecological modeling: constructs and tests models toexplain and predict how ecological systems work– Grounded in actual data and based on hypotheses– Extremely useful in large, intricate systems that are hard to

isolate and study– Example: studying the flow of nutrients into the

Chesapeake Bay and oyster responses to changing waterconditions

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Ecosystems provide vital services

• All life on Earth (including humans) depends on healthy,functioning ecosystems

• Ecosystem services: essential services provided byhealthy, normally functioning ecosystems– When human activities damage ecosystems, we must

devote resources to supply these services ourselves– Example: if we kill off insect predators, farmers must use

synthetic pesticides that harm people and wildlife• One of the most important ecosystem services:

– Nutrients cycle through the environment in intricate ways


Ecological processes provide services


Nutrients circulate through ecosystems

• Nutrients move through the environment in complex ways– Matter is continually circulated in an ecosystem

• Nutrient (biogeochemical) cycle: the movement ofnutrients through ecosystems

• Pool (reservoir): a location where nutrients remain forvarying amounts of time (residence time)

• Source: a reservoir releases more materials than it accepts• Sink: a reservoir that are accepts more than it releases• Flux: the rate at which materials move between reservoirs

– Can change over time


Humans affect nutrient cycling

• Human activities affect nutrient cycling– Altering fluxes, residence times, and amounts of nutrients

in reservoirs

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The water cycle affects all other cycles

• Water is essential for biochemical reactions and isinvolved in nearly every environmental system and cycle

• Hydrologic cycle: the flow of liquid, gaseous, and solidwater through the environment– Less than 1% is available as fresh water

• Evaporation: conversion of liquid to gaseous water• Transpiration: release of water vapor by plants• Precipitation: rain or snow returns water to Earth’s

surface• Runoff: water flows into streams, lakes, rivers, oceans


Water is also stored underground

• Infiltration: water soaks down through rock and soil torecharge aquifers

• Aquifers: underground reservoirs of spongelike regionsof rock and soil that hold …– Groundwater: water found underground beneath layers

of soil• Water table: the uppermost level of groundwater held

in an aquifer• Water in aquifers may be ancient (thousands of years

old)


The hydrologic cycle


Human impacts on the hydrologic cycle

• Humans have affected almost every flux, reservoir, andresidence time in the water cycle

• Damming rivers slows water movement and increasesevaporation

• Removal of vegetation increases runoff and erosionwhile decreasing infiltration and transpiration

• Overdrawing surface and groundwater for agriculture,industry, and domestic uses lowers water tables

• Emitting air pollutants that dissolve in water changesthe nature of precipitation and decreases cleansing

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The carbon cycle

• Carbon cycle: describes carbon’s route in theenvironment– Carbon forms essential biological molecules

• Through photosynthesis, producers move carbon from theair and water to organisms– Respiration returns carbon to the air and water

• Oceans are the second largest reservoir of carbon– Absorb carbon from the air, land, and organisms

• Decomposition returns carbon to the sediment, the largestreservoir of carbon– Ultimately, it may be converted into fossil fuels


The carbon cycle


Humans affect the carbon cycle

• Burning fossil fuels moves carbon from the ground to theair– Since mid-1700s, people have added over 275 billion tons

of carbon dioxide to the atmosphere• Cutting forests and burning fields moves carbon from

organisms to the air– Less carbon dioxide is removed by photosynthesis

• Today’s atmospheric carbon dioxide reservoir is thelargest in the past 800,000 years– The driving force behind climate change


The nitrogen cycle involves bacteria

• Nitrogen makes up 78% of the atmosphere• It is contained in proteins, DNA, and RNA

– It is also essential for plant growth• Nitrogen cycle: describes the routes of nitrogen

through the environment– Nitrogen gas is inert and cannot be used by organisms

• It needs lightning, bacteria, or human intervention tobecome biologically active and available to organisms– Then it is a potent fertilizer

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Nitrogen must become biologically available

• Nitrogen fixation: nitrogen-fixing soil bacteria orlightning “fixes” nitrogen gas into ammonium– Nitrogen-fixing bacteria live in legumes (e.g., soybeans)

• Nitrification: bacteria then convert ammonium ions firstinto nitrite ions then into nitrate ions– Plants can take up these ions

• Nitrite and nitrate also come from the air or fertilizers• Animals obtain nitrogen by eating plants or other animals• Denitrifying bacteria: convert nitrates in soil or water to

gaseous nitrogen, releasing it back into the atmosphere


The nitrogen cycle


Humans greatly affect the nitrogen cycle

• Historically, nitrogen fixation was a bottleneck: limitedthe flux of nitrogen from air into water-soluble forms

• Industrial fixation fixes nitrogen on a massive scale– Overwhelming nature’s denitrification abilities

• Excess nitrogen leads to hypoxia in coastal areas• Nitrogen-based fertilizers strip the soil of other

nutrients– Reducing soil fertility

• Burning forests and fossil fuels leads to acidprecipitation, adds greenhouse gases, and createsphotochemical smog


The phosphorus cycle

• Phosphorus cycle: describes the routes that phosphorustakes through the environment– No significant atmospheric component– Most phosphorus is in rocks

• With naturally low environmental concentrations,phosphorus is a limiting factor for plant growth

• Weathering releases phosphorus into water– Allowing it to be taken up by plants

• Phosphorus is a key component of cell membranes,DNA, RNA, and other biochemical compounds

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The phosphorus cycle


Humans affect the phosphorus cycle

• Fertilizer from lawns and farmlands– Increases phosphorus in soil– Its runoff into water increases phytoplankton blooms and

hypoxia• Wastewater containing detergents releases phosphorus to

waterways


Controlling nutrient pollution in waterways

• Reduce fertilizer use in farms and lawns• Change timing of fertilizer applications to minimize

runoff• Manage livestock manure applications to farmland• Plant vegetation “buffers” around streams to trap

runoff• Restore wetlands and create artificial ones to filter

runoff• Improve sewage-treatment technologies• Restore frequently flooded lands• Reduce fossil fuel combustion


Conclusion

• Life interacts with its abiotic environment in ecosystemsthrough which energy flows and materials are recycled

• Understanding biogeochemical cycles is crucial– Humans are changing the ways those cycles function

• Understanding energy, energy flow, and chemistryincreases our understanding of organisms– How environmental systems function

• Thinking in terms of systems can teach us how to:– Avoid disrupting Earth’s processes and to mitigate any

disruptions we cause

central case study: vanishing oysters of matter, … 02, 2012 · matter, energy, and ecosystems ......

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