Environmental Science Chapter 2

Front 1

Central Case Study: Vanishing Oysters of the Chesapeake Bay

Back 1

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

Front 2

System

Back 2

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

Front 3

Feedback loop

Back 3

a circular process in which a system’s output serves as input to that same system

Front 4

Negative feedback loop

Back 4

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

Front 5

Positive feedback loop

Back 5

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

Front 6

Lithosphere

Back 6

rock and sediment

Front 7

Atmosphere

Back 7

the air surrounding the planet

Front 8

Hydrosphere

Back 8

all water on Earth

Front 9

Biosphere

Back 9

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

Front 10

The Chesapeake Bay: a systems perspective

Back 10

The Chesapeake Bay and rivers that empty into it are an interacting system:
It receives very high levels of nitrogen and phosphorus from agriculture from 6 states, and air pollution from 15 states

Front 11

Sources of nitrogen and phosphorus entering the Chesapeake Bay - watershed Definition

Back 11

Nitrogen and phosphorus enter the Chesapeake watershed (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 deplete oxygen, causing…
Fish and other aquatic organisms to flee or suffocate

Front 12

Eutrophication

Back 12

the process of
Nutrient over enrichment, blooms of algae, increased production of organic matter, and ecosystem degradation

Front 13

Eutrophication in aquatic systems

Back 13

Front 14

Global hypoxic dead zones

Back 14

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

Front 15

People are changing the chemistry of Earth’s systems

Back 15

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

Front 16

Matter

Back 16

all material in the universe that has mass and occupies space
It can be solid, liquid, or gas

Front 17

Law of conservation of matter

Back 17

: 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 pollution and waste away

Front 18

Element

Back 18

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

Front 19

Nutrients

Back 19

elements needed in large amounts by organisms
Examples: carbon, nitrogen, calcium

Front 20

Atoms

Back 20

the smallest components that maintain an element’s chemical properties

Front 21

protons & neutrons

Back 21

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

Front 22

Atomic number

Back 22

the number of protons

Front 23

Electrons

Back 23

: negatively charged particles surrounding the nucleus
Balance the protons’ positive charge

Front 24

The structure of an atom

Back 24

Front 25

Isotopes

Back 25

atoms of an element with different numbers of neutrons

Front 26

Mass number

Back 26

the number of protons + neutrons
Isotopes of an element behave slightly differently

Front 27

Ions

Back 27

atoms that gain or lose electrons
They are electrically charged

Front 28

Radioactive isotopes

Back 28

Radioactive isotopes shed subatomic particles and emit high-energy radiation.

They decay until they become nonradioactive stable isotopes

Front 29

Half-life:

Back 29

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

Front 30

Molecules and compounds

Back 30

An attraction for each other’s electrons bonds atoms

Front 31

Molecules

Back 31

combinations of two or more atoms

Front 32

Chemical formula

Back 32

indicates the type and number of atoms in the molecule (oxygen gas: O2)

Front 33

Compound

Back 33

: a molecule composed of atoms of two or more different elements
Water: two hydrogen atoms bonded to one oxygen atom: H2O

Front 34

Carbon dioxide

Back 34

one carbon atom with two oxygen atoms: CO2

Front 35

Ionic bonds

Back 35

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

Front 36

Covalent bond

Back 36

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

Front 37

Solutions

Back 37

electrons, molecules and compounds come together with no chemical bonding
Air contains O2, N2, H2O, CO2, methane (CH4), ozone (O3)
Human blood, ocean water, plant sap, metal alloys

Front 38

Hydrogen ions determine acidity

Back 38

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

Front 39

Matter is composed of compounds

Back 39

Living things depend on organic compounds

Front 40

Organic compounds

Back 40

carbon atoms bonded together
They may include other elements: nitrogen, oxygen, sulfur, and phosphorus

Carbon can be linked in elaborate chains, rings, other structures
Forming millions of different organic compounds

Front 41

Inorganic compounds

Back 41

lack the carbon–carbon bond

Front 42

Hydrocarbons

Back 42

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

Front 43

Polymers

Back 43

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

Front 44

Macromolecules

Back 44

large-sized molecules essential to life

Front 45

Proteins are long chains of amino acids

Back 45

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)

Front 46

enzymes

Back 46

They can serve as enzymes: molecules that promote (catalyze) chemical reactions

Front 47

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

Back 47

carry hereditary information of organisms

Front 48

Nucleic acids

Back 48

long chains of nucleotides that contain sugar, phosphate,and a nitrogen base

Front 49

Genes

Back 49

regions of DNA that code for proteins that perform certain functions

Front 50

Carbohydrates

Back 50

: 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 found in cell walls of plants

Front 51

Lipids

Back 51

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

Front 52

cells

Back 52

All living things are composed of cells: the most basic unit of organismal organization

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

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Eukaryotes

Back 53

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

Front 54

Prokaryotes

Back 54

bacteria and archaea
Single-celled, lacking membrane-enclosed nucleus and organelles

Front 55

Energy

Back 55

an intangible phenomenon that can change the position, physical composition, temperature of matter
Involved in biological, chemical, physical processes

Front 56

Potential energy

Back 56

energy of position

Front 57

Kinetic energy

Back 57

energy of motion

Front 58

Chemical energy

Back 58

potential energy held in the bonds between atoms

Changing potential into kinetic energy
Releases energy
Produces motion, action, or heat

Front 59

Potential vs. kinetic energy

Back 59

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

Front 60

First law of thermodynamics

Back 60

energy can change form but cannot be created or destroyed

Front 61

Second law of thermodynamics

Back 61

energy changes from a more-ordered to a less-ordered state

Front 62

Entropy

Back 62

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

Front 63

The sun’s energy powers living systems

Back 63

Energy that powers Earth’s ecological systems comes mainly from the sun
The sun releases radiation from the electromagnetic spectrum
Some is visible light

Front 64

Autotrophs (producers)

Back 64

organisms that use the sun’s energy to produce their own food
Plants, algae, cyanobacteria

Front 65

Photosynthesis ---- Will be on TEST

Back 65

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

Front 66

Photosynthesis produces food

Back 66

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)

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

Front 67

Cellular respiration releases energy

Back 67

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

Front 68

Heterotrophs

Back 68

organisms that gain energy by feeding on others
Animals, fungi, microbes
The energy is used for cellular tasks

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

Front 69

Ecosystem

Back 69

all organisms and nonliving entities occurring and interacting in a particular area
Animals, plants, water, soil, nutrients, etc.
Biological entities are tightly intertwined with the chemical and physical aspects of their environment

For example, in the Chesapeake Bay estuary (a water body 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

Front 70

Energy and matter flow through ecosystems

Back 70

Sun energy flows in one direction through ecosystems
Energy is processed and transformed

Front 71

Energy and matter flow through ecosystems

Back 71

Matter is recycled within ecosystems
Outputs: heat, water flow, and waste

Front 72

Primary production

Back 72

conversion of solar energy to chemical energy in sugars by autotrophs during photosynthesis

Front 73

Gross primary production

Back 73

total amount of chemical energy produced by autotrophs
Most energy is used to power their own metabolism

Front 74

Net primary production

Back 74

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

Front 75

Productivity

Back 75

rate at which autotrophs convert energy to biomass

Front 76

High net primary productivity:

Back 76

ecosystems whose plants rapidly convert solar energy to biomass

Front 77

A global map of net primary productivity

Back 77

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

Front 78

Ecosystems interact across landscapes

Back 78

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

Front 79

Landscape ecology & Patches

Back 79

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

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

This landscape consists of a mosaic of patches of 5 ecosystems

Front 80

Conservation biologists

Back 80

study the loss, protection, and restoration of biodiversity
Humans are dividing habitat into small, isolated patches
Corridors of habitat can link patches
Populations of organisms have specific habitat requirements
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 to link patches to preserve biodiversity

Front 81

Model

Back 81

a simplified representation of a complicated natural process
Helps us understand processes and make predictions

Front 82

Ecological modeling

Back 82

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

Front 83

Ecosystem services

Back 83

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

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

One of the most important ecosystem services:
Nutrients cycle through the environment in intricate ways

Front 84

Ecological processes provide services

Back 84

Front 85

Nutrient (biogeochemical) cycle

Back 85

Nutrients move through the environment in complex ways
Matter is continually circulated in an ecosystem
Nutrient (biogeochemical) cycle: the movement of nutrients through ecosystems

Pool (reservoir): a location where nutrients remain for varying 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

Front 86

Humans affect nutrient cycling

Back 86

Human activities affect nutrient cycling
Altering fluxes, residence times, and amounts of nutrients in reservoirs

Front 87

The water cycle affects all other cycles

Back 87

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

Hydrologic cycle: the flow of liquid, gaseous, and solid water 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

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Water is also stored underground

Back 88

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)

Front 89

The hydrologic cycle

Back 89

Front 90

Human impacts on the hydrologic cycle

Back 90

-Humans have affected almost every flux, reservoir, and residence time in 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

Front 91

Carbon cycle

Back 91

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

Front 92

Humans affect the carbon cycle

Back 92

Burning fossil fuels moves carbon from the ground to the air
-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 the largest in the past 800,000 years
-The driving force behind climate change

Front 93

The nitrogen cycle involves bacteria

Back 93

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

Front 94

Nitrogen must become biologically available

Back 94

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
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

Front 95

Humans greatly affect the nitrogen cycle

Industrial fixation

Back 95

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
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 acid precipitation, adds greenhouse gases, and creates photochemical smog

Front 96

Phosphorus cycle

Back 96

describes the routes that phosphorus takes 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

Front 97

Humans affect the phosphorus cycle

Back 97

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

Front 98

Controlling nutrient pollution in waterways

Back 98

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

Front 99

Conclusion

Back 99

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:
-Avoid disrupting Earth’s processes and to mitigate any disruptions we cause