Ecosystems: What Are
They and How Do They
Work?
Chapter 3
Importance of Insects

Pollination

Pest control

Important roles in
biological community
Fig. 4-A, p. 64
Nature of Ecology

What is ecology?

Organisms

Cells

Species

Microbes rule!
Fig. 3-2, p. 37
Populations, Communities, and
Ecosystems

Populations

Genetic diversity

Biological community

Ecosystems

Biosphere
Population of Monarch
Butterflies
Fig. 4-3, p. 63
Genetic Diversity in One Snail
Species
Fig. 4-3, p. 63
What Sustains Life on Earth?

Troposphere

Stratosphere

Hydrosphere

Lithosphere

Biosphere
Fig. 3-2, p. 42
Earth’s Life-Support Systems

One way flow of
high-quality energy

Cycling of matter

Gravity
Fig. 3-6, p. 39
Flow of Solar Energy to and from
the Earth

Greenhouse gases

Greenhouse effect
Fig. 3-3, p. 42
Flow of Solar Energy to and from
the Earth
Solar
radiation
Energy in = Energy out
Reflected by
atmosphere (34%)
UV radiation
Radiated by
atmosphere
as heat (66%)
Lower Stratosphere
(ozone layer)
Absorbed
by ozone
Visible
light
Troposphere
Greenhouse
effect
Heat
Absorbed
by the
earth
Heat radiated
by the earth
Fig. 3-3, p. 42
Why is the Earth so Favorable
for Life?

Liquid water

Temperature

Gravity

Atmosphere
Ecosystem Components

Biomes

Aquatic life zones

Freshwater life zones

Ocean or marine life zones

Abiotic and biotic components

Range of tolerance

Law of tolerance
Major Biomes
Average annual precipitation
100–125 cm (40–50 in.)
75–100 cm (30–40 in.)
50–75 cm (20–30 in.)
25–50 cm (10–20 in.)
below 25 cm (0–10 in.)
4,600 m (15,000 ft.)
3,000 m (10,000 ft.)
1,500 m (5,000 ft.)
Coastal mountain
ranges
Coastal chaparral
and scrub
Sierra Nevada
Mountains
Great American
Desert
Coniferous forest
Rocky
Mountains
Desert
Great
Plains
Coniferous forest
Mississippi
River Valley
Prairie grassland
Appalachian
Mountains
Deciduous forest
Fig. 3-8, p. 41
Major Components of Freshwater Ecosystems
Sun
Producers (rooted plants)
Producers (phytoplankton)
Primary consumers (zooplankton)
Secondary consumers (fish)
Tertiary
consumers
(turtles)
Dissolved
chemicals
Sediment
Decomposers (bacteria and fungi)
Fig. 3-9, p. 42
Major Components of a Field
Ecosystem
Oxygen (O2)
Sun
Producer
Carbon dioxide (CO2)
Primary consumer
(rabbit)
Falling leaves
Precipitation
and twigs
Secondary consumer
(fox)
Producers
Soil decomposers
Water
Soluble mineral nutrients
Fig. 3-10, p. 42
Range of Tolerance
Lower limit
of tolerance
Few
organisms
Abundance of organisms
Few
organisms
No
organisms
Population Size
No
organisms
Upper limit
of tolerance
Zone of
intolerance
Low
Zone of
physiological stress
Optimum range
Temperature
Zone of
Zone of
intolerance
physiological stress
High
Fig. 3-11, p. 43
Factors Limiting Population Growth

Limiting factors

Limiting factor principle

Excess water or water shortages for terrestrial organisms

Excess or lack of soil nutrients

Dissolved oxygen for aquatic organisms

Salinity for aquatic organisms
Major Biological Components of
Ecosystems

Producers (autotrophs)

Photosynthesis

Chemosynthesis

Consumers (heterotrophs)
Consumers: Feeding and
Respiration

Decomposers

Omnivores

Detritivores

Aerobic respiration
Detritivores
Detritus feeders
Long-horned
beetle holes
Bark beetle
engraving
Carpenter
ant
galleries
Termite and
carpenter
ant
work
Decomposers
Dry rot fungus
Wood
reduced
to powder
Time progression
Mushroom
Powder broken down by decomposers
into plant nutrients in soil
Fig. 3-8, p. 45
Main Structural Components of
an Ecosystem
Heat
Abiotic chemicals
(carbon dioxide,
oxygen, nitrogen,
minerals)
Heat
Solar
energy
Heat
Producers
(plants)
Decomposers
bacteria, fungi)
Heat
Consumers
(herbivores,
carnivores)
Heat
Fig. 3-9, p. 46
Biodiversity
Fig. 3-14, p. 45
Examples of Biodiversity
Fig. 3-15, p. 46
Food Chains and Food Webs

Food chain

Trophic level

Food web
Model of a Food Chain
First Trophic
Level
Producers
(plants)
Heat
Second Trophic
Level
Third Trophic
Level
Fourth Trophic
Level
Primary
consumers
(herbivores)
Secondary
consumers
(carnivores)
Tertiary
consumers
(top carnivores)
Heat
Heat
Solar
energy
Heat Heat
Heat
Heat
Detritivores
decomposers and detritus feeders)
Heat
Fig. 3-10, p. 47
Food Web in the Antarctic
Humans
Sperm whale
Blue whale
Elephant
seal
Killer whale
Crabeater seal
Leopard
seal
Adélie
penguins
Petrel
Emperor
penguin
Fish
Squid
Carnivorous plankton
Herbivorous
zooplankton
Krill
Phytoplankton
Fig. 3-11, p. 48
Energy Flow in an Ecosystem

Biomass

Ecological efficiency

Pyramid of energy flow
Pyramid of Energy Flow
Heat
Heat
Tertiary
consumers
(human)
Decomposers
Heat
10
Secondary
consumers
(perch)
100
1,000
10,000
Usable energy
available at
each tropic level
(in kilocalories)
Heat
Primary
consumers
(zooplankton)
Heat
Producers
(phytoplankton)
Fig. 3-12, p. 49
Biomass Productivity

Gross primary productivity (GPP)

Net primary productivity (NPP)

NPP and populations
Differences between GPP and NPP
Sun
Respiration
Gross primary
production
Growth and reproduction
Energy lost and
unavailable to
consumers
Net primary
production
(energy
available to
consumers)
Fig. 3-19, p. 49
Net Primary Productivity in Major
Life Zones and Ecosystems
Terrestrial Ecosystems
Swamps and marshes
Tropical rain forest
Temperate forest
Northern coniferous forest
(taiga)
Savanna
Agricultural land
Woodland and shrubland
Temperate grassland
Tundra (arctic and alpine)
Desert scrub
Extreme desert
Aquatic Ecosystems
Estuaries
Lakes and streams
Continental shelf
Open ocean
800
1,600
2,400
3,200
4,000
4,800
5,600
6,400
7,200
8,000
8,800 9,600
Average net primary productivity (kcal/m2/yr)
Fig. 3-13 p. 49
Soils

Origins of soils

Soil horizons: O, A, B, and C

Soil profiles

Infiltration and leaching
Soil Formation and Horizons
Oak tree
Wood
sorrel
Lords and
ladies
Dog violet
Earthworm
Fern
Millipede
Honey
fungus
Mole
Grasses and Organic debris
small shrubs builds up
Moss and Rock
fragments
lichen
O horizon
Leaf litter
A horizon
Topsoil
Bedrock
B horizon
Subsoil
Immature soil
Regolith
Young soil
Pseudoscorpion
Mite
C horizon
Parent
material
Nematode
Root system
Mature soil
Red earth
Springtail
Fungus
mite
Bacteria
Actinomycetes
Fig.10-A, p. 209
Soil Profiles
from Different
Ecosystems
Fig. 3-22, p. 52
Soil Profiles from Different
Ecosystems
Mosaic
of closely
packed
pebbles,
boulders
Alkaline,
dark,
and rich
in humus
Weak humusmineral mixture
Dry, brown to
reddish-brown, with
variable accumulations
of clay, calcium
carbonate, and
soluble salts
Desert Soil
(hot, dry climate)
Clay,
calcium
compounds
Grassland Soil
(semiarid climate)
Fig. 3-22a, p. 52
Soil Profiles from Different
Ecosystems
Forest litter
leaf mold
Acidic
lightcolored
humus
Humus-mineral
mixture
Light-colored
and acidic
Light, grayishbrown, silt loam
Iron and
aluminum
compounds
mixed with
clay
Tropical Rain Forest Soil
(humid, tropical climate)
Acid litter
and humus
Humus and
iron and
aluminum
compounds
Dark brown
Firm clay
Deciduous Forest Soil
(humid, mild climate)
Coniferous Forest Soil
(humid, cold climate)
Fig. 3-22b, p. 52
pH

Acidity or alkalinity of water or water-bearing samples

Scale 0-14

Acidic: pH 0-6.9

Neutral pH 7.0

Alkaline (basic): pH 7.1-14
The pH Scale
Fig. 3-23, p. 192
Matter Cycling in Ecosystems:
Biogeochemical Cycles

Nutrient (biogeochemical) cycles

Hydrologic (water) cycle

Carbon cycle

Nitrogen cycle

Phosphorus cycle

Sulfur cycle
Simplified Hydrologic (Water) Cycle
Condensation
Rain clouds
Transpiration
Precipitation
Precipitation
to land
Transpiration
from plants
Rapid
Surface runoff
(rapid)
Evaporation
Evaporation
From
land
Precipitation
Evaporation
From
ocean
Precipitatio
n
to ocean
Surface
runoff
(rapid)
Infiltration and
percolation
Groundwater movement (slow)
Ocean storage
Fig. 3-14, p. 51
Human Intervention in the
Hydrologic Cycle

Large withdraw of surface and ground waters

Clearing vegetation

Pollution
The Carbon Cycle (Marine)
Diffusion between
atmosphere and ocean
Carbon dioxide
dissolved in
ocean water
photosynthesis
Combustion of fossil fuels
aerobic
respiration
Marine food webs
Producers, consumers,
decomposers, detritivores
incorporation
death,
into sediments sedimentation
uplifting over
geologic time
sedimentation
Marine sediments, including
formations with fossil fuels
Fig. 3-15 p. 53
The Carbon Cycle (Terrestrial)
Atmosphere
(most carbon is in carbon dioxide)
Combustion
of fossil
fuels
volcanic action
Terrestrial
rocks
weathering
photosynthesis
aerobic
respiration
Land food webs
Producers, consumers,
decomposers,
detritivores
combustion of
wood (for clearing
land; or fuel)
deforestaion
Soil water
(dissolved carbon)
death, burial, compaction over geologic time
Peat,
fossil fuels
leaching,
runoff
Fig. 3-15, p. 53
Human Interference in the Global
Carbon Cycle
High
projection
Low
projection
Fig. 3-26, p. 56
The Nitrogen Cycle
Gaseous Nitrogen (N2)
in Atmosphere
Nitrogen
Fixation
by industry
for agriculture
Food Webs
on Land
Fertilizers
uptake by
autotroph
s
excretion, death,
decomposition
uptake by
autotroph
s
Nitrogen Fixation
bacteria convert N2 to
ammonia (NH3); this
dissolves to form
ammonium (NH4+)
NH3, NH4+
in Soil
loss by
leaching
Nitrogenous Wastes,
Remains in Soil
Ammonification
NO3–
in Soil
by bacteria
2. Nitrification
bacteria, fungi convert the
residues to NH3; this
dissolves to form NH4+
bacteria convert NO2–
to nitrate (NO3–)
1. Nitrification
NO2–
in Soil
bacteria convert NH4+
to nitrite (NO2–)
Denitrification
loss by
leaching
Fig. 3-16 p. 54
Human Interference in the Global
Nitrogen Cycle
Nitrogen fixation by natural processes
Nitrogen
Fig. 3-28, p. 58
The Phosphorus Cycle
mining
Fertilizer
Guano
excretion
agriculture
uptake by
autotrophs
Marine
Food Webs
uptake by
autotrophs
Dissolved
in Ocean
Water
leaching, runoff
Dissolved
in Soil Water,
Lakes, Rivers
death,
decomposition
sedimentation
Land
Food
Webs
weathering
weathering
settling out
uplifting over
geologic time
Marine Sediments
Rocks
Fig. 3-17, p. 55
The Sulfur Cycle
Water
Sulfur trioxide
Ammonia
Ammonium sulfate
Oxygen
Sulfur dioxide
Acidic fog and precipitation
Sulfuric acid
Hydrogen sulfide
Plants
Volcano
Dimethyl sulfide
Animals
Industries
Ocean
Sulfate salts
Metallic
Sulfide
deposits
Decaying matter
Sulfur
Hydrogen sulfide
Fig. 3-18, p. 56
How Do Ecologists Learn
about Ecosystems?

Field research

Remote sensing

Geographic information system (GIS)

Laboratory research

Systems analysis
Geographic Information System (GIS)
Critical nesting site locations
Private
owner 1
USDA
Forest Service
USDA Forest Service
Private owner 2
Topography
Forest
Wetland
Habitat type
Lake
Grassland
Real world
Fig. 3-31, p. 61
Stages of Systems Analysis
Systems
Measurement
Define objectives
Identify and inventory variables
Obtain baseline data on variables
Data
Analysis
Make statistical analysis of relationships among variables
System
Modeling
Construct mathematical model
describing interactions among variables
System
Simulation
System
Optimization
Determine significant interactions
Run the model on a computer, with
values entered for different variables
Evaluate best ways to achieve objectivesStepped
Art
Fig. 3-32, p. 61
Importance of Baseline
Ecological Data

To understand nature, current conditions must
be known

Baseline data are lacking

Long-term sustainability