Chapter 3

Environmental Systems:

Chemistry, Energy, and Ecosystems

PowerPoint® Slides prepared by

Jay Withgott and Heidi Marcum

This lecture will help you understand:

• The nature of environmental systems

• The fundamentals of environmental chemistry

• The molecular building blocks of organisms

• Energy and energy flow• Photosynthesis and respiration• Ecosystems and interactions• Fundamentals of landscape

ecology• Carbon, phosphorus, nitrogen, and

water cycles

What is a Dead Zone?

Its Not Just Us

Central Case: The Gulf of Mexico’s “Dead Zone”

• Gulf of Mexico used to bring in 600 million kg/year shrimp, fish, and shellfish

• Gulf “dead zone”: a region of water so depleted of oxygen that marine organisms are killed or driven away

• In 2000, this zone encompassed 22,000 km2 (8,500 mi2) — an area larger than New Jersey.

• Hypoxia: low concentrations of dissolved oxygen water – Caused by fertilizer, runoff, sewage

• The U.S. government proposed that farmers reduce fertilizer use.

The Earth’s systems

• 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

• Feedback loop: a system’s output serves as input to that same system– A circular process

Negative feedback loop• Negative feedback loop: output resulting from a

system moving in one direction acts as an input that moves the system in the other direction– Input and output neutralize one another– Stabilizes the system– Example: body temperature– Most systems in nature

Positive feedback loop• Positive feedback loop: instead of stabilizing a

system, it drives it further toward an extreme• Examples: erosion• Rare in nature

– But are common in natural systems altered by humans

Cntd• Negative Feedback Loop:

A change in which the variable being regulated brings about a response that moves the variable in the "opposite direction". for example you are inside and at normal body temperature(variable) then you go outside into the cold and your body temp begins to decrease(unintended event), your body responds by causing events that raise your temperature(intentional change) "back up to its original value"(raising your temp that was falling). this is mostly seen in homeostasis and you dont have to go outside for your body to do this because it is constantly happening all the time.

Positive Feedback loop:this type of feedback loop accelerates a process and usually has no obvious means of being slowed or stopped. Think of an avalanche that started as a small snowball rolling down a steep hill. One example is child birth in mammals. A positive feedback loop occurs when a baby's head is pushed against the birth canal. the nerve signals from smooth muscle cells of the birth canal send info to the brain which then triggers a hormone release from the petuitary glands. the hormones then cause those "same smooth muscle cells" in the birth canal to contract with more force, which causes more signals to be sent to the brain and so on until the fetus is delivered

Environmental systems interact• Natural systems are divided into

categories– Lithosphere: rock and sediment– Atmosphere: the air surrounding the planet– Hydrosphere: all water on earth– Biosphere: the planet’s living organisms

• Categorizing systems allows humans to understand earth’s complexity.– Most systems overlap

The Gulf of Mexico: a systems perspective

Very high levels of nutrients such as nitrogen and phosphorus from a variety of sources cause the abnormally low levels of oxygen in the Gulf of Mexico.

Where it Begins

Eutrophication in the Gulf of Mexico

• Nutrients (nitrogen and phosphorus) from various Midwestern sources enter the Mississippi River, which causes….

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

• Bacteria eat dead phytoplankton and wastes and deplete oxygen, causing…

• Fish and other aquatic organisms to suffocate

• Eutrophication: the process of nutrient overenrichment, blooms of algae, increased production of organic matter, and ecosystem degradation

Eutrophication

Activity

• Read article Independently and Quietly in class• AFTER everyone in class has completed the

reading assignment, you can work in pairs to complete the writing assignment. We will discuss your points tomorrow in class

• Look at the different projects I have created for you. You will be responsible for completing one on the due date.

Chemistry is crucial for understanding…

• Any environmental issue:– How gases contribute to global climate change– How pollutants cause acid rain– The effects of chemicals on the health of wildlife

and people– Water pollution– Wastewater treatment– Hazardous waste– Atmospheric ozone depletion – Energy issues

Chemical building blocks• Matter: all material in the universe that has

mass and occupies space– Can be transformed from one type of substance

into others– But it cannot be destroyed or created, which is…– The law of conservation of matter

• Helps us understand that the amount of matter stays constant

• Recycled in nutrient cycles and ecosystems

Chemical building blocks

• Element: a fundamental type of matter, with a given set of properties– Chemists recognize 92 elements in nature and

20 artificially created ones.– Elements abundant in nature: carbon, nitrogen,

hydrogen and oxygen– Periodic table of the elements summarizes

information on the elements

Elements are composed of atoms

– Atoms: the smallest components that maintain an element’s chemical properties

– The atom’s nucleus has protons (positively charged particles) and neutrons (particles lacking electric charge).

– Atomic number: the atom’s number of protons– Electrons: negatively charged particles surrounding the

nucleus that balance the positively charged protons – Atoms may also gain or lose electrons to become ions —

electrically charged atoms.

The structure of an atom

Chemical building blocks

• Isotopes: atoms with differing numbers of neutrons– Mass number: the number of

protons and neutrons– Isotopes of an element behave

differently.– Some isotopes are radioactive.

• They decay until they become non-radioactive stable isotopes.

• Emit high-energy radiation

Radioactive decay

• Half-life: the amount of time it takes for one-half of the atoms to give off radiation and decay– Different radioscopes 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• Molecules: combinations of two or more atoms:

Covalently Bonded– Oxygen gas: O2

• Compounds: a molecule composed of atoms of two or more different elements– Water: two hydrogen atoms bonded to one oxygen atom

(H20)

– Carbon dioxide: one carbon atom with two oxygen atoms (CO2)

• Solutions: no chemical bonding, but is a mixture of substances (i.e., blood, ocean water)

Hydrogen ions determine acidity• The pH scale ranges from 0 to 14

and quantifies the acidity or basicity of solutions.– Acidic solutions have a pH less than 7. – Basic solutions have a pH greater than

7.– Neutral solutions have a pH of 7 (i.e.,

pure water).

• A substance with pH of 6 contains 10 times as many hydrogen ions as a substance with pH of 7.

Activity:

• Outline pages 49-56

Organic Compounds• Organic compounds: carbon atoms joined by

bonds that may include other elements – Such as nitrogen, oxygen, sulfur, and phosphorus

• Hydrocarbons: contain only carbon and hydrogen– Make up fossil fuels– The simplest hydrocarbon is methane (natural gas)– Can be a gas, liquid, or solid

Macromolecules: life’s building blocks

• Polymers: long chains of repeated molecules– The building blocks of life

• Macromolecules: large-size molecules– Three types of polymers are essential to life:

• Proteins• Nucleic acids• Carbohydrates

– Lipids are not polymers, but are also essential.

Proteins• Produce tissues, provide structural support,

store energy, and transport substances– Made up of chains of amino acids– Animal proteins generate skin, hair, muscles,

and tendons– Some function as components of the immune

system– Can serve as enzymes — molecules that

promote chemical reactions

A special process involving proteins

• Nucleic acid: directs the production of proteins– Deoxyribonucleic acid (DNA) and ribonucleic acid

(RNA) carry the hereditary information of organisms.• Long chains of nucleotides that contain sugar, phosphate,

and a nitrogen base

• Genes: regions of DNA that code for

proteins that perform certain functions

Carbohydrates and lipids• Carbohydrates: atoms of carbon, hydrogen, and

oxygen– Sugars: simple carbohydrates, 3-7 carbons long

• Glucose: provides energy for cells

– Complex carbohydrates build structures and store energy• Starch: used by plants to store energy• Animals eat plants to acquire starch.• Cellulose of plants and shells of insects

• Lipids: a chemically diverse group of compounds grouped together because they don’t dissolve in water– Energy, cell membranes, structural support, and hormones

Cells compartmentalize macromolecules

• Cell: the basic unit of life’s organization

• Eukaryotes: contain a membrane-enclosed nucleus and various organelles that perform specific functions– Plants, animals, fungi, protists

• Prokaryotes: single-celled organisms lacking organelles and a nucleus– Bacteria and archaea

Activity:

• Testing your comprehension questions #1-4

• Seeking Solutions questions #1 and 5

• Dead Zone Questions/Scenario

Activity: 8/31/12

• After presenting Scenario 1 or 2, Work on the following:

• Kinetic vs. Potential Energy

• Explain how Photosynthesis works

• Relate photosynthesis to Primary Productivity

• Compare Photosynthesis to Cellular Respiration

Energy fundamentals• Energy: an intangible phenomenon that can change the

position, physical composition, or temperature of matter– Potential energy: energy of position

– Kinetic energy: energy of motion

– Chemical energy: potential energy held in the bonds between atoms

• Potential energy is changed into kinetic energy to produce motion, action, and heat.

Energy is conserved...but changes in quality

• First law of thermodynamics: energy can change forms, but cannot be created or destroyed

• Second law of thermodynamics: the nature of energy changes from a more-ordered to a less-ordered state if no force counteracts this tendency– Entropy: an increasing state of disorder– For example, burning a log of firewood transforms the log

from a highly organized product into light and heat energy, gases, smoke, and carbon ash.

The sun’s energy powers life• The energy that powers Earth’s ecological

systems originates mainly from the sun.• The sun releases radiation from the

electromagnetic spectrum.– Some is visible light

Photosynthesis• Autotrophs (producers): produce

their own food from the sun’s energy – Green plants, algae, and cyanobacteria

• Photosynthesis: the process of turning light energy from the sun into chemical energy– Carbon dioxide + water + sun’s energy

is converted into sugars and high-quality energy.

– Low-quality energy is turned into high-quality energy.

Photosynthesis produces food

• Chloroplasts: organelles where photosynthesis occurs– Contain chlorophyll: a light-absorbing pigment– Light reaction: solar energy is used to split water to

form oxygen and a small, high-energy molecule that fuels the….

– Calvin cycle: links carbon atoms from carbon dioxide into sugar (glucose)

6CO2 + 6H20 + the sun’s energy C6H12O6 + 6O2

Cellular respiration releases chemical energy

• Organisms can use chemical energy created by photosynthesis through cellular respiration.– Oxygen is used to convert glucose into water + carbon

dioxide + energy.– Only 2/3 of the original energy input per glucose molecule

is gained in respiration.– Occurs in autotrophs and organisms that feed on others

• Heterotrophs (consumers): organisms that gain energy by feeding on others– Animals, fungi, microbes

C6H12O6 + 6O2 6CO2 + 6H20 + energy

Energy and matter in ecosystems

• Ecosystem: all organisms and non-living entities occurring and interacting in a particular area

–Animals, plants, water, soil, nutrients, etc.

• Energy from the sun flows in one direction through ecosystems.

• Energy is processed and transformed.• Matter is recycled within ecosystems.

• Outputs: heat, water flow, and waste

Energy is converted to biomass

• Primary production: conversion of solar energy to chemical energy by autotrophs – Gross primary production: assimilation of energy by

autotrophs– Net primary production (NPP): energy remaining

after respiration, used to generate biomass– Available for heterotrophs

• Productivity: rate at which autotrophs convert energy to biomass

Net primary productivity of ecosystems

High net primary productivity: ecosystems whose plants rapidly convert solar energy to biomass

A global map of NPP

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

Nutrients can limit productivity

• Nutrients: elements and compounds that organisms consume and require for survival– Stimulate plant production– Lack of nutrients can limit production.– Nitrogen and phosphorus are important for plant and

algal growth.• Oceanic primary productivity is highest in water

near shore.– Over 200 dead zones now exist due to nutrient

pollution.

Nutrient runoff devastates aquatic systems

• Aquatic dead zones result from nutrient pollution from farms, cities, and industry.– Most dead zones are located near Europe and the

eastern U.S. • Scientists are investigating innovative and

economical ways to reduce nutrient runoff.

Phytoplankton blooms off the Louisiana coast.

Ecosystems come in different sizes

• Ecosystems vary greatly in size.

• 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

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

• Patches: ecosystems, communities, or habitat form the landscape and are distributed in complex patterns (a mosaic)

Landscape ecology

This landscape consists of a mosaic of patches of 5 ecosystems.

Conservation biology• If a habitat is distributed in patches, organisms face

danger in traveling from one patch to another.– Patches spaced too far apart prevent travel

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

• Geographic information systems (GIS): computer software that layers multiple types of satellite data to create a complete picture of a landscape– Geology, vegetation, animal species, and human

development

Activity:

• Testing Your Comprehension Questions #5-7

• Calculating Ecological Footprints

• HW: Complete the “Testing Your Comprehension” Questions, 8-10 after reading pages 63-69; Biogeochemical Cycles

Nutrients circulate through ecosystems

• Physical matter is circulated continually in an ecosystem.

• Nutrient (biogeochemical) cycle: the movement of nutrients through ecosystems– Pools (reservoirs): where nutrients remain for

varying amounts of time

– Flux: movement of nutrients among pools• Can change over time

The carbon cycle• Carbon cycle: describes the routes that carbon atoms

take through the environment• Through photosynthesis, producers move carbon from the

air and water to organisms.• Respiration returns carbon to the air and oceans.• Decomposition returns carbon to the sediment, the largest

reservoir of carbon.– Ultimately, it may be converted into fossil fuels.

• The world’s oceans are the second largest reservoir.– Obtain carbon from the air and organisms

The carbon cycle

Humans affect the carbon cycle

• Burning fossil fuels moves carbon from the ground to the air.

• Cutting forests and burning fields moves carbon from organisms to the air.

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

The phosphorus cycle• Phosphorus cycle: describes the routes that

phosphorus atoms take through the environment– No significant atmospheric component– Most phosphorus is within rocks and is released by

weathering.

• 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.

The phosphorus cycle

Humans affect the phosphorus cycle

• Mining rocks for fertilizer moves phosphorus from the soil to water systems.

• Wastewater discharge also releases phosphorus, which boosts algal growth and causes eutrophication.

• May be present in detergents– Consumers should purchase phosphate-free detergents.

The nitrogen cycle• Nitrogen comprises 78% of our atmosphere and

is contained in proteins, DNA, and RNA.

• Nitrogen cycle: describes the routes that nitrogen atoms take through the environment– Nitrogen gas is inert and cannot be used by organisms.

– Needs lightning, bacteria, or human intervention

• Nitrogen fixation: Nitrogen gas is combined (fixed) with hydrogen by nitrogen-fixing bacteria or lightning to become ammonium– Can be used by plants

– Nitrogen-fixing bacteria live in legumes (i.e., soybeans)

Nitrification and denitrification

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

• 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 affect nitrogen cycle• Excess nitrogen leads to hypoxia in coastal areas.• Synthetic fertilizers doubled the rate of Earth’s nitrogen

fixation. • Burning forests and fossil fuels leads to acid precipitation.• Wetland destruction and increased planting of legumes has

increased nitrogen-rich compounds on land and in water.• Increased emissions of nitrogen-containing greenhouse gases• Calcium and potassium in soil are washed out by fertilizers.• Reduced biodiversity of plants adapted to low-nitrogen soils.• Changed estuaries and coastal ecosystems and fisheries

Human inputs of nitrogen into the environment

Fully half of nitrogen entering the environment is of human origin.

A law addressing hypoxia in the Gulf

• The Harmful Algal Bloom and Hypoxia Research and Control Act (1998) called for an assessment of hypoxia in the Gulf and to:– Reduce nitrogen fertilizer use in Midwestern farms– Change timing of fertilizer applications to minimize runoff– Use alternative crops– Manage livestock manure– Restore wetlands and create artificial ones– Improve sewage-treatment technologies– Evaluate these approaches

• This Act has worked, and was reauthorized in 2003.

The hydrologic cycle• Water is essential for biochemical reactions and is involved

in nearly every environmental system.• Hydrologic cycle: summarizes how liquid, gaseous, and

solid water flows through the environment– Oceans are the main reservoir.– Less than 1% is available as fresh water.

• Evaporation: water moves from aquatic and land systems to air

• Transpiration: release of water vapor by plants• Precipitation: condensation of water vapor as rain or snow

returns water from the air to Earth’s surface

Groundwater

– Aquifers: underground reservoirs of spongelike regions of rock and soil that hold …

– Groundwater: water found underground beneath layers of soil

– Water table: the upper limit of groundwater held in an aquifer

– Water may be ancient (thousands of years old).

The hydrologic cycle

Human impacts on hydrologic cycle

• Damming rivers increases evaporation and infiltration into aquifers.

• Altering the surface and vegetation increases runoff and erosion.

• Spreading water on agricultural fields depletes rivers, lakes, and streams and increases evaporation.

• Overdrawing groundwater for drinking, irrigation, and industrial uses depletes groundwater resources.

• Removing forests and vegetation reduces transpiration and lowers water tables.

• Emitting pollutants changes the nature of precipitation.

Activity: 9/4/12• Carbon Cycle- 2

• Phosphorus- 2

• Nitrogen- 4– Nitrification– Denitrificaiton

• Hydrologic- 3

• Create brochure, pamphlet, etc. explaining each in detail.

Conclusion• Life interacts with its abiotic environment in ecosystems

through which energy flows and materials are recycled.• Understanding biogeochemical cycles is crucial.

– Humans are causing significant changes in the ways those cycles function.

• Understanding energy, energy flow, and chemistry increases our understanding of organisms, their environment, and how environmental systems function.

• Thinking in terms of systems can teach us how to avoid disrupting Earth’s processes and how to mitigate any disruptions we cause.

QUESTION: ReviewWhich of the following part of an atom has a positive charge?a) Proton

b) Neutron

c) Electron

d) Hydrogen

e) Neutreno

QUESTION: ReviewWhich of the following consists of a chemically diverse group of compounds that don’t dissolve in water?

a) Nucleic acids

b) Proteins

c) Carbohydrates

d) Lipids

e) Polymers

QUESTION: ReviewSugars, starches, and glucose are all:

a) Lipids

b) Proteins

c) Carbohydrates

d) Nucleic acids

e) Synthetic molecules

QUESTION: ReviewAccording to the first law of thermodynamics:

a) Energy cannot be created or destroyed

b) Things tend to move toward a more disorderly state

c) Matter can be created, but not energy

d) Kinetic energy is the most efficient source of energy

e) Energy is constantly recycled

QUESTION: ReviewWhich of the following organisms is an autotroph?

a) Deep-sea tubeworm

b) Horse

c) Pine tree

d) Human

e) None of these

QUESTION: ReviewA transitional zone between two ecosystems

is a(n):a) Conservation zone

b) Corridor

c) Reservoir

d) Ecotone

e) Patch

QUESTION: ReviewHumans have affected the nitrogen cycle in all of the following ways EXCEPT:

a) Doubling the rate of nitrogen fixation

b) Increasing emissions of greenhouse gases

c) Lowering water tables

d) Changing estuaries and coastal ecosystems

e) Reducing diversity of plants adapted to nitrogen-poor soils

QUESTION: Weighing the Issues

Who should be responsible for reducing nitrogen pollution and eutrophication off coastal waters?

a) Fishermen, since they reap the benefits of fishing

b) Farmers, since they are causing much of the problem

c) Taxpayers, since they are getting both fish and food

d) The federal government, since it’s job is to protect American citizens and the environment

QUESTION: Interpreting Graphs and Data

A molecule of the hydrocarbon ethane contains:

a) 10 carbon atoms and 8 hydrogen atoms

b) 8 carbon molecules and 10 hydrogen enzymes

c) 2 carbon atoms and 6 hydrogen atoms

d) 2 different ions

QUESTION: Interpreting Graphs and Data

Which is the most basic material?

a) Lemon juice

b) Acid rain

c) Rainwater

d) Seawater

e) Soft soap

QUESTION: Interpreting Graphs and Data

According to this graph, which ecosystem has the lowest amount of biomass?

a) Temperate grassland

b) Boreal forest c) Savannad) Tropical

rainforest