Chapter. Environmental Systems: Matter, Energy, and Ecosystems. Lecture Questions prepared by Reggie Cobb Nash Community College

Transcription

1 Chapter 2 Environmental Systems: Matter, Energy, and Ecosystems Lecture Questions prepared by Reggie Cobb Nash Community College

2 This lecture will help you understand: Environmental systems Fundamentals of matter and chemistry Energy and energy flow Photosynthesis and cellular respiration Ecosystems and interactions Fundamentals of landscape ecology Ecosystem services Various chemical cycles

3 Central Case Study: The Vanishing Oysters of the Chesapeake Bay Chesapeake Bay was the world s largest oyster fishery Overharvesting, pollution, and habitat destruction ruined it The economy lost $4 billion from 1980 to 2010 Strict pollution standards and oyster restoration efforts give reason for hope

4 Earth s environmental systems Understanding human impacts on the environment requires understanding complex environmental systems A system A network of relationships among components that 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

5 Environmental systems interact Structural spheres of Earth s systems 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

6 Systems involve feedback loops Feedback loop A circular process in which a system s output serves as input to that same system Negative feedback loop Stabilizes a system: output that results when the system moves in one direction acts as an input that moves the system in the other direction When balanced, the system is in dynamic equilibrium Positive feedback loop Drives a system further toward an extreme instead of stabilizing it

7 Systems involve feedback loops (Cont d) Negative feedback loop Example: If we get hot, we sweat; sweating cools down the body Most systems in nature involve negative feedback loops that allow them to maintain homeostasis

8 Systems involve feedback loops (Cont d) Positive feedback loop Example Runaway cycles of positive feedback are rare in nature but are common in natural systems altered by humans

9 Frequently Asked Question But isn t positive feedback good and negative feedback bad?

10 Environmental systems interact The Chesapeake Bay and rivers that empty into it are an interacting system It receives agricultural runoff from 6 states containing very high levels of nitrogen and phosphorus, and it receives air pollution from 15 states in its airshed

11 Sources of nitrogen and phosphorus entering the Chesapeake Bay

12 Eutrophication in the Chesapeake Bay Eutrophication The process of nutrient overenrichment; characterized by blooms of algae, increased production of organic matter, and ecosystem degradation Example Nitrogen and phosphorus enter the Chesapeake Bay, causing Phytoplankton (microscopic algae and bacteria) to grow; then Bacteria eat dead phytoplankton and wastes and deplete oxygen, causing Fish and other aquatic organisms to flee or suffocate

13 Eutrophication in aquatic systems

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

15 Matter, chemistry, and the environment Matter All material in the universe that has mass and occupies space It can be solid, liquid, or gas Chemistry Study of types of matter and their interactions 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

16 Matter, chemistry, and the environment (Cont d) Law of conservation of matter Matter can be transformed 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 away pollution and waste

17 Atoms and elements are chemical building blocks Element A chemical substance with a given set of properties Examples: nitrogen, phosphorus, oxygen 92 natural and 20 artificially created elements exist Nutrients Elements that organisms need in large amounts Examples: carbon, nitrogen, calcium

18 Atoms and elements are chemical building blocks (Cont d) Atom Smallest component of an element The atom s nucleus (center) includes Protons (positively charged particles) Neutrons (lacking electric charge) Surrounding the nucleus are Electrons (negatively charged particles) Atomic number The number of protons Mass number Protons plus neutrons (particles in nucleus)

19 The structure of an atom

20 Isotopes and ions Isotopes Atoms of an element with different numbers of neutrons Different mass numbers Isotopes of an element behave slightly differently Ions Atoms that gain or lose electrons They are electrically charged

21 Some isotopes are radioactive and decay Radioisotopes Shed subatomic particles and emit high-energy radiation 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

22 Atoms bond to form molecules and compounds Molecules Combinations of two or more atoms Compound A molecule composed of atoms of two or more different elements Chemical formula Indicates the type and number of atoms in a molecule or compound Examples Oxygen gas: O 2 Water: H 2 O Carbon dioxide: CO 2

23 Atoms are held together with bonds Ionic bonds Ions of different charges bind together Example: table salt (NaCl) Covalent bond Atoms without electrical charges share electrons Example: hydrogen gas (H 2 )

24 Atoms are held together with bonds (Cont d) Solutions Elements, molecules, and compounds come together with no chemical bonding Examples Air is a solution containing O 2, N 2, H 2 O, CO 2, methane (CH 4 ), ozone (O 3 ) Human blood, ocean water, plant sap, metal alloys

25 Hydrogen ions determine acidity Water can split into H + and OH - The ph scale quantifies the acidity 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

26 Matter is composed of organic and inorganic 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, other structures Inorganic compounds Lack the carbon carbon bond

27 Matter is composed of organic and inorganic compounds (Cont d) Hydrocarbons Organic compounds that contain only carbon and hydrogen The simplest hydrocarbon is methane (natural gas) Fossil fuels consist of hydrocarbons Crude oil contains hundreds of types of hydrocarbons

28 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 they are also essential Fats, oils, phospholipids, waxes, steroids Macromolecules Large-sized molecules essential to life

29 Macromolecules are building blocks of life (Cont d) Proteins Long chains of amino acids Comprise most of an organism s matter Produce tissues, provide structural support, store energy, transport material Some are components of the immune system or hormones (chemical messengers) Can serve as enzymes Molecules that catalyze (promote) chemical reactions Animals use proteins to generate skin, hair, muscles, and tendons

30 Macromolecules are building blocks of life (Cont d) Nucleic acids Long chains of nucleotides that contain sugar, phosphate, and a nitrogen base Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) carry hereditary information of organisms Genes Regions of DNA that code for proteins that perform certain functions

31 Macromolecules are building blocks of life (Cont d) Carbohydrates Include simple sugars and large molecules 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 is found in cell walls of plants Lipids Do not dissolve in water Fats and oils (energy), waxes (structure), steroids

32 Organisms use cells to compartmentalize macromolecules Cells Most basic unit of organismal organization Simplest component of all living things Vary in size, shape, and function Classified according to their structure Eukaryotes: plants, animals, fungi, protists Contain a membrane-enclosed nucleus Membrane-enclosed organelles do specific things Prokaryotes: bacteria and archaea Single-celled, lacking membrane-enclosed nucleus and organelles

33 Energy fundamentals Energy An intangible phenomenon that can change the position, 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

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

35 Energy is always conserved, but changes in quality First law of thermodynamics Energy can change form but cannot be created or destroyed Second law of thermodynamics Energy changes from a more-ordered to a less-ordered state Entropy: an increasing state of disorder Living organisms resist entropy by getting energy from food and photosynthesis Dead organisms get no energy and through decomposition lose their organized structure

36 Light energy from the sun powers most living systems Energy that powers Earth s ecological systems comes mainly from the sun The sun releases radiation from the electromagnetic spectrum Some is visible light

37 Light energy from the sun powers most living systems (Cont d) Autotrophs (producers) Organisms that use the sun s energy to produce their own food Plants, algae, cyanobacteria Photosynthesis The process of turning the sun s light energy into high-quality chemical energy Sunlight converts carbon dioxide and water into sugars Moving to lower entropy

38 Photosynthesis produces food Photosynthesis occurs in chloroplasts Chloroplasts contain chlorophyll (a light-absorbing pigment) Two stages of photosynthesis Light reactions Solar energy splits water and creates high-energy molecules that fuel the Calvin cycle Calvin cycle Links carbon atoms from carbon dioxide into sugar (glucose) Photosynthesis chemical reaction 6CO 2 + 6H 2 O + the sun s energy C 6 H 12 O 6 (sugar) + 6O 2

39 Cellular respiration releases chemical energy Cellular respiration Occurs in all living things (plants, animals, etc.) Organisms use chemical energy created by photosynthesis Oxygen breaks the high-energy chemical glucose bonds Energy is used to make other chemical bonds or tasks Heterotrophs (consumers) Organisms that gain energy by feeding on others Animals, fungi, microbes Cellular respiration reaction C 6 H 12 O 6 (sugar) + 6O 2 6CO 2 + 6H 2 O + energy

40 Ecosystems Ecosystem All organisms and nonliving entities occurring and interacting in a particular area Animals, plants, water, soil, nutrients, etc. Biological entities Tightly intertwined with the chemical and physical aspects of their environment Example: the Chesapeake Bay estuary 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

41 Energy flows and matter cycle through ecosystems Sun energy flows in one direction through ecosystems Energy is processed and transformed Matter is recycled within ecosystems Outputs: heat, water flow, and waste

42 Energy is converted to chemical energy in biomass Primary production Conversion of solar energy to chemical energy in sugars by autotrophs during photosynthesis Gross primary production Total amount of chemical energy produced by autotrophs Most energy is used to power their own metabolism Net primary production Energy remaining after respiration Equals gross primary production minus cellular respiration It is used to generate biomass (leaves, stems, roots) Available for heterotrophs

43 Net primary productivity of ecosystems Productivity Rate at which autotrophs convert energy to biomass High net primary productivity Ecosystems whose plants rapidly convert solar energy to biomass

44 Ecosystems interact across landscapes Ecotones Transitional zones between two ecosystems in which elements of each ecosystem mix Landscape ecology The study of how landscape structure affects the abundance, distribution, and interaction of organisms Useful for studying migrating birds, fish, mammals Helpful for planning sustainable regional development Geographic information systems (GIS) Use computer software to layer multiple types of data together Help to view ecosystems on a larger geographic scale

45 Ecosystems interact across landscapes (Cont d) Patches Ecosystems, communities, or habitat form the landscape and are distributed in complex patterns (a mosaic) Conservation biologists Study the loss, protection, and restoration of biodiversity They have a great interest in landscape ecology Corridors of habitat can link patches to preserve biodiversity Humans are responsible for dividing habitats into small, isolated patches

46 Ecosystems interact across landscapes (Cont d) This landscape consists of a mosaic of five ecosystems

47 Weighing the Issues Ecosystems Where You Live Think about the area where you live, and briefly describe the region s ecosystems. How do they interact? Does any water pass from one to another? Describe the boundaries of watersheds in your region. If one ecosystem were greatly modified, what impacts on nearby systems might result?

48 Modeling helps us understand ecosystems Model A simplified representation of a complicated natural process Helps us understand processes and make predictions Ecological modeling Constructs and tests models to explain 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 water conditions

49 Modeling helps us understand ecosystems (Cont d) Ecological modelers Observe relationships among variables in nature and then construct models to explain those relationships and make predictions

50 Ecosystems services sustain our world All life on Earth (including humans) depends on healthy, functioning ecosystems Ecosystem services Essential services provided by healthy, 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

51 Ecosystems services sustain our world (Cont d)

52 Nutrients circulate through ecosystems in biochemical cycles Nutrients move through the environment in complex ways Matter is continually circulated in an ecosystem Nutrient (biogeochemical) cycle The movement of nutrients through ecosystems Involves two main types of pools (reservoirs) Source Sink

53 Nutrients circulate through ecosystems in biochemical cycles (Cont d) Pool (reservoir) a location where nutrients remain for varying amounts of time (residence time) Source a reservoir that releases more materials than it accepts Sink a reservoir that accepts more than it releases Flux the rate at which materials move between reservoirs; can change over time

54 The water cycle affects all other cycles Water is essential for biochemical reactions and is involved in nearly every environmental system and cycle Hydrologic cycle The flow of liquid/gaseous/solid water through environment More than 97% of water is in oceans Less than 1% is readily available fresh water Evaporation conversion of liquid to gaseous water Transpiration release of water vapor by plants Precipitation return of water to Earth s surface in the form of rain/snow

55 Water is also stored underground Infiltration Water soaks down through rock and soil to recharge aquifers Aquifers Underground reservoirs of spongelike regions of 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)

56 The water (hydrologic) cycle Gray arrows represent fluxes among reservoirs

57 Human impact on the water cycle Humans have affected almost every aspect of the water cycle Damming rivers slows water movement and increases evaporation Removal of vegetation increases runoff and erosion while decreasing infiltration and transpiration Overdrawing surface and groundwater for agriculture, industry, and domestic uses lowers water tables Emitting air pollutants that dissolve in water changes the nature of precipitation and decreases cleansing

58 The carbon cycle circulates a vital organic nutrient Carbon cycle Describes carbon s route in the environment Carbon forms essential biological molecules Through photosynthesis, producers move carbon from the air 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 largest reservoir of carbon Ultimately, it may be converted into fossil fuels

59 The carbon cycle

60 Human impact on the carbon cycle Burning fossil fuels moves carbon from the ground to the air Since mid-1700s, people have added over 276 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 the largest in the past 800,000 years The driving force behind anthropogenic global climate change

61 The nitrogen cycle involves specialized 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 to become biologically active and available to organisms Then it is a potent fertilizer

62 The nitrogen cycle involves specialized bacteria (Cont d) Nitrogen fixation Nitrogen-fixing soil bacteria or lightning fixes nitrogen gas into ammonium Nitrogen-fixing bacteria live in legumes (e.g., soybeans) Nitrification Bacteria then convert ammonium ions first into nitrite ions then into nitrate ions that plants can take up Animals obtain nitrogen by eating plants or other animals Denitrification completes the nitrogen cycle Denitrifying bacteria convert nitrates in soil or water to gaseous nitrogen, releasing it back into the atmosphere

63 The nitrogen cycle

64 We have greatly influenced the nitrogen cycle Historically, nitrogen fixation was a bottleneck: limited the flux of nitrogen from air into water-soluble forms Industrial fixation fixes nitrogen on a massive scale Human alteration of nitrogen cycle Overwhelms nature s denitrification abilities Excess nitrogen leads to hypoxia in coastal areas Nitrogen-based fertilizers strip the soil of other nutrients, thereby reducing soil fertility Burning forests and fossil fuels leads to acid precipitation, adds greenhouse gases, and creates photochemical smog

65 The phosphorus cycle circulates a limited nutrient Phosphorus cycle Describes the routes that phosphorus takes through the environment No significant atmospheric component Most phosphorus is in rocks Weathering releases phosphorus into water Allows it to be taken up by plants With naturally low environmental concentrations, phosphorus is a limiting factor for plant growth Phosphorus is a key component of cell membranes, DNA, RNA, and other biochemical compounds

66 The phosphorus cycle

67 Humans impact on 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 into waterways

68 Tackling nutrient enrichment requires diverse approaches Reduce fertilizer use on farms and lawns Change timing of fertilizer applications to minimize rainy-season runoff Manage manure applications to farmland Plant vegetation buffers around streams to trap nutrient and sediment runoff Construct wetlands to filter stormwater and runoff Restore wetlands along waterways Improve sewage-treatment technologies Upgrade stormwater system to capture runoff Reduce fossil fuel combustion

69 Tackling nutrient enrichment requires diverse approaches (Cont d) The cost per pound of reducing nitrogen inputs into the Chesapeake Bay varies widely.

70 Weighing the Issues Nutrient Pollution and Its Financial Impacts Large amount of nitrogen and phosphorous entering the Chesapeake Bay originates from farms and other sources far from the bay. People leaving near the bay, such as oystermen, bear many of the negative impacts. Who do you believe should be responsible for addressing the problems? Should environmental policies on this issue be developed and enforced by state governments, federal governments, both, or neither? Explain the reasons for your answer.

71 A systematic approach to restoration offers hope for the Chesapeake Bay Collaborative efforts of concerned citizens, advocacy organizations, EPA, and state governments After 25 years of failed pollution control agreements and $6 billion spent on cleanup efforts, the Chesapeake Bay Foundation (CBF) sued the EPA in January 2009 In late 2010 a pollution budget was developed and implemented by EPA with assistance of seven states around the Bay Reducing nutrient and sediment inputs into the bay and limiting harvests of oysters, crabs, and fish are already yielding some evident improvements to the bay s health

72 Conclusion Life interacts with its abiotic environment in ecosystems through 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 chemistry increases our understanding of organisms How environmental systems function Thinking in terms of systems Can teach us how to void disrupting Earth s processes and to mitigate any disruptions we cause