Ecosystems: What Are They and How
Do They Work?
G. Tyler Miller’s
Living in the Environment
14th Edition
Chapter 4
Essential Questions / Objectives
Define ecology. List and distinguish among five levels of organization of
matter that are the focus of the realm of ecology
List the characteristics of life
Distinguish among lithosphere, hydrosphere, atmosphere, and ecosphere.
Briefly describe how the sun, gravity, and nutrient cycles sustain life on
Earth. Compare the flow of matter and the flow of energy through the
biosphere
Define soil horizon. Briefly describe 4 soil layers. Using Figure 4-25 on p.
75 in the text, compare soil profiles of five important soil types
Describe a fertile soil. In doing so, be sure to refer to soil texture, porosity,
loam, and acidity
Essential Questions / Objectives
Distinguish between an open system and a closed system. Name and
describe three types of biogeochemical cycles
Define abiotic component of an ecosystem. List three important physical
factors and three important chemical factors that have large effects on
ecosystems
Summarize the law of tolerance. Compare limiting factors in terrestrial and
aquatic ecosystems
Define biotic component of an ecosystem. Distinguish between producers
and consumers. List and distinguish four types of consumers. Distinguish
among scavengers, detritus feeders and decomposers. Distinguish
between photosynthesizers and chemosynthesizers; aerobic respiration
and anaerobic respiration
Essential Questions / Objectives
Distinguish between food chains and food webs; a grazing food web and
detrital food web. Apply the second law of energy to food chains and
pyramids of energy, which describe energy flow in ecosystems. Explain
how there may be exceptions to pyramids of numbers and biomass, but
not energy
Evaluate which ecosystems show the highest average net primary
productivity and which contribute most to global net primary productivity
Briefly describe the historical development and distinguishing features of
three approaches ecologists use to learn about ecosystems: field
research, laboratory research, and systems analysis
Define ecosystem service. List five examples of ecosystem services.
Distinguish among three types of biodiversity. Briefly state two principles
to sustain ecosystems
What is Ecology?
Ecology is the study of the interactions of living organisms
with one another and with their nonliving environment of
matter and energy; study of the structure and functions of
nature
What roles do insects
play?
Ecosystem Organization Overview
Biosphere- Zone of earth where life is found. It consists of
parts of the atmosphere (the troposphere),
hydrosphere (mostly surface water and groundwater),
and lithosphere (mostly soil and surface rocks and
sediments on the bottoms of oceans and other bodies
of water) where life is found. Sometimes called the
ecosphere
Ecosystems- Community of different species interacting
with one another and with the chemical and physical
factors making up its nonliving environment
Communities- Populations of all species living and
interacting in an area at a particular time
Populations- Group of individual organisms of the same
species living in a particular area
Organisms Any form of life (species)- group of organisms
that resemble one another in appearance, behavior,
chemical makeup and processes, and genetic
structure. Organisms that reproduce sexually are
classified as members of the same species only if they
can actually or potentially interbreed with one another
and produce fertile offspring
What are the Characteristics of Life?
All things living have the following
specific properties:
Known species
1,412,000
Cellular organization
Other animals
281,000
Metabolism
Homeostasis
Reproduction
Heredity
Fungi
69,000
Insects
751,000
Prokaryotes
4,800
About 1.4 million species have
been identified, but estimates
of number of species range
from 3.6 million to 100 million
Plants
248,400
Protists
57,700
Cells: The Basic Unit of Life
Energy
Conversion
Mitochondria
Prokaryotic Cell
Nucleus
(information
storage)
Eukaryotic Cell
Protein
construction
and energy
conversion
occur without
specialized
internal
structures
DNA
(information
storage, no
nucleus)
Cell membrane
(transport of
raw materials
and finished
products)
Protein
Construction
ER
Packaging
Golgi Body
Ecosystem Organization Details
Populations- Group of individual organisms of the same species living in a particular
area, but not all populations are exactly the same. Characteristics of populations
include:
Genetic diversity explains why these individuals may not behave nor look exactly alike
Habitat is the place where a population or an individual usually lives
Distribution (range) is the area over which a species may be found.
A population of Monarch butterflies. The geographic
distribution coincides with that of the milkweed plant on
which the larvae feed
The genetic diversity among individuals of one species of
Caribbean Snail is reflected in the variations in shell color
and banding patterns
The Earth’s Life-Support Systems
Atmosphere The whole mass of air
surrounding the earth.
Troposphere Innermost layer of the
atmosphere. It contains about 75%
of the mass of earth's air and
extends about 17 kilometers (11
miles) above sea level.
Stratosphere Second layer of the
atmosphere, extending about 17-48
kilometers (11-30 miles) above the
earth's surface. It contains small
amounts of gaseous ozone (O3),
which filters out about 95% of the
incoming harmful ultraviolet (UV)
radiation emitted by the sun.
Hydrosphere The earth's liquid water
(oceans, lakes, other bodies of
surface water, and underground
water), frozen water (polar ice
caps, floating ice caps, and ice in
soil, known as permafrost), and
water vapor in the atmosphere
Lithosphere Outer shell of the earth, composed
of the crust and the rigid, outermost part of
the mantle outside the asthenosphere;
material found in earth's plates
Natural Capital: Sustaining Life of Earth Flow of Energy to
and from the Earth
From the sun to the Earth
One-way flow of energy from Sun
Cycling of Crucial Elements
Gravity
Flow of Energy to and from the Earth
The amount of energy
received and
topography of a region
determines climate.
Terrestrial parts of the
biosphere are classified
as biomes, areas such
as deserts, forests, and
grasslands.
Aquatic life zones
describe the many
different areas found in
a water environment,
such as freshwater or
marine life zones (coral
reefs, coastal estuaries,
deep ocean).
Fig. 4-9 p. 61
Major Biomes and the Role of Climate
The amount of energy
received and topography
of a region determines
climate.
Terrestrial parts of the
biosphere are classified as
biomes, areas such as
deserts, forests, and
grasslands.
Aquatic life zones
describe the many
different areas found in a
water environment, such
as freshwater or marine
life zones (coral reefs,
coastal estuaries, deep
ocean).
Biomes of the World
Tropic of
Cancer
Equator
Tropic of
Capricorn
Arctic tundra (polar grasslands)
Desert
Boreal forest (taiga), evergreen coniferous
forest (e.g., montane coniferous forest)
Tropical rain forest,
tropical evergreen forest
Semidesert,
arid grassland
Mountains
(complex zonation)
Temperate deciduous forest
Tropical deciduous forest
Ice
Temperate grassland
Tropical scrub forest
Dry woodlands and
shrublands (chaparral)
Tropical savanna,
thorn forest
Aquatic Life Zones-Marine and freshwater portions of the biosphere. Examples include
freshwater life zones (such as lakes and streams) and ocean or marine life zones
High tide
Low tide
Sun
Sea level
50
Euphotic Zone
100
Estuarine
Zone
Continental
shelf
Photosynthesis
0
200
500
Bathyal Zone
1,000
Twilight
Coastal Zone Open Sea
Depth in
meters
1,500
2,000
3,000
Marine Life Zones
4,000
5,000
10,000
Darkness
Abyssal Zone
Ecosystem
Components
The major components of
ecosystems are abiotic
(nonliving) water, air,
nutrients, solar energy, and
biotic (living) plants,
animals, and microbes.
Ecosystem Factors
Ecosystem characteristics include a range of
tolerance to physical and chemical
environments by the ecosystem's
populations Law of tolerance: The
distribution of a species in an ecosystem is
determined by the levels of one or more
physical or chemical factors being within the
range tolerated by that species.
Aquatic life zones can be limited by the
dissolved oxygen (DO) content in the water,
temperature, pH or by the salinity
Sugar Maple
The limiting factor principle
states that too much or too
little of any abiotic factor can
limit or prevent growth of a
population, even if all other
factors are at or near the
optimum range of tolerance.
An abiotic factor such as lack
of water or poor soil can be
understood here
Ecosystem Components
The major biological components of ecosystems
are the producers/autotrophs that are self-feeders
and the consumers/heterotrophs.
Autotrophs photosynthesize making their own
food from compounds in the environment
(organisms such as green plants and algae). A few
specialized producers can convert simple
compounds to more complex compounds without
sunlight, a process called chemosynthesis.
Heterotrophs (consumers) feed on other
organisms or their remains.
Herbivores feed on plants.
Carnivores feed on animals.
Omnivores feed on both plants and animals.
Detritivores feed on dead organic matter and
break it down into smaller molecules
Decomposers (bacteria/fungi) break down
organic detritus into simpler inorganic
compounds.
Detritivores and Decomposer
Detritus feeders
Bark beetle
engraving
Long-horned
beetle holes
Carpenter
ant
galleries
Decomposers
Termite and
carpenter
ant
work
Dry rot fungus
Wood
reduced
to powder
Time progression
Mushroom
Powder broken down by decomposers
into plant nutrients in soil
Ecosystem Components
Glucose and other organic compounds are broken down and energy
released by the process of aerobic respiration, the use of oxygen to
convert organic matter back to carbon dioxide and water. This process
is a net chemical change to that of photosynthesis.
Photosynthesis: CO2 + H2O
Carbon
dioxide
water
CO2 + H2O
Light
C6H12O6 + O2
Glucose
sugar
oxygen
C6H12O6 + O2 Aerobic Respiration
“Cellular Respiration”
Some decomposers are able to break down organic compounds without
using oxygen. This process is called anaerobic respiration, or
fermentation. The end products are compounds such as methane gas,
ethyl alcohol, acetic acid, and hydrogen sulfide.
Matter is recycled; there is a one-way
flow of energy.
Biological Diversity (Biodiversity)
Biodiversity is the amazing variety of earth's genes, species, ecosystems, and
ecosystem processes.
The kinds of biodiversity are:
Genetic diversity: the variety of genetic material with a species or population
Species diversity: the number of species present in different habitats
Ecological diversity: the variety of terrestrial and aquatic ecosystems found in an
area or on the earth
Functional diversity: the biological and chemical processes such as energy flow
and mater cycling needed for the survival of species, communities, and
ecosystems
 Human cultural diversity is included as part of the earth's biodiversity by
some people.
 Biodiversity keeps us alive and supports our economies.
 Biodiversity is a renewable resource as long as humans live off the interest,
not destroy the capital.
Food Chains and Energy Flow in Ecosystems
Food chains and food webs
help us understand how
eaters, the eaten, and the
decomposed are
interconnected in an
ecosystem.
The sequence of organisms as
they are eaten is a food chain.
Food webs are complex
networks of interconnected
food chains. They are maps of
life's interdependence.
Trophic levels are feeding levels for organisms within an ecosystem,(1) Producers
belong to the first trophic level. (2) Primary consumers belong to the second trophic
level.(3)Secondary consumers belong to the (4) third trophic level.Detritivores and
decomposers process detritus from all trophic levels.
Energy flow in a food web/chain decreases at each succeeding organism in a chain or
web. The dry weight of all organic matter within the organisms of a food chain/web is
called biomass.
Tropic Levels
Humans
Blue whale
Ecological efficiency is the
term that describes the
percentage of usable energy
transferred as biomass from
one trophic level to another
and ranges from 2%-40%
with 10% being typical.
Sperm whale
Killer
whale
Elephant
seal
Crabeater seal
Leopard
seal
The greater number of
trophic levels in a food chain,
the greater loss of usable
energy.
Emperor
penguin
Adélie
penguins
Petrel
Squid
Fish
Carnivorous plankton
Herbivorous
zooplankton
Krill
Phytoplankton
Ecological Pyramids
Pyramid of energy flow
The pyramid of energy flow
visualizes the loss of usable
energy through a food
chain. The lower levels of
the trophic pyramid support
more organisms. If people
eat at a lower trophic level
(fruits, vegetables, grains
directly consumed), Earth
can support more people.
There is a large loss of
energy between successive
trophic levels.
Pyramid of biomass
Compares biomass (The dry
weight of all organic matter
within the organisms of a
food chain/web) at each
trophic level
Pyramid of numbers
Compares the total number of organism at each
trophic level
Primary Productivity of Ecosystems
Gross primary productivity (GPP) The rate at which an
ecosystem's producers capture and store a given
amount of chemical energy as biomass in a given
length of time.
Net primary productivity (NPP) Rate at which all the
plants in an ecosystem produce net useful chemical
energy; equal to the difference between the rate at
which the plants in an ecosystem produce useful
chemical energy (gross primary productivity) and the
rate at which they use some of that energy through
cellular respiration.
The three most productive
systems are swamps and
marshes, tropical rain
forests, and estuaries.
The three least productive
are tundra, desert scrub,
and extreme desert.
Figure4-22
p.71
On land - Dark
green highest
GPP / Brown
or White lowest
GPP
At Sea: Red,
Orange, yellow,
green, light
blue, dark blue
(highest GGP
to lowest)
The planet's NPP limits the number of consumers who can survive on Earth.
The highly productive tropical rain forest cannot support agriculture as practiced in
developed countries.
Marshes and swamps do not produce food that can be eaten directly by humans;
they feed other aquatic species that humans consume (fish, shrimp, clams).
Humans are using, wasting, and destroying biomass faster than producers can
make it.
Soils
Importance
Soil provides nutrients needed for plant growth; it helps purify water. It is
a thin covering that is made of eroded rock, minerals, decaying
organic matter, water, air, and billions of living organisms.
Mature soils have developed over a long time, are arranged in soil
horizons (series of horizontal layers), and have distinct textures and
compositions in these layers that vary among different types of soils.
Layers of soil, called soil horizons, vary in number, composition, and
thickness.
Soil Formation and Generalized Soil Profile
Horizons
The top part/layer is the surface litter layer or O horizon. This layer is
brown/black and composed of leaves, twigs, crop wastes, animal
waste, fungi, and other organic material.
The topsoil layer or A horizon is composed of decomposed organic
matter called humus, as well as some inorganic mineral particles.
Thick topsoil layers help hold water and nutrients. These two top
layers teem with bacteria, fungi, earthworms, and small insects.
Air and water fill spaces between soil particles. Plant roots need
oxygen for aerobic respiration.
The B horizon (subsoil) and the C-horizon (parent material) have
most of the soil's inorganic matter—sand, silt, clay, and gravel. The
C-horizon rests on bedrock.
soil texture
Relative amounts of
the different types
and sizes of mineral
particles in a sample
of soil.
soil permeability
Rate at which water
and air move from
upper to lower soil
layers.
porosity
Soil is a complex mixture of inorganic minerals
(clay, silt, pebbles, and sand), decaying organic
matter, water, air, and living organisms
Percentage of space
in rock or soil
occupied by voids,
whether the voids are
isolated or
connected.
Soil Profiles in
Different
Biomes
Dark-brown/black
topsoil is rich in
nitrogen and organic
matter.
Gray, yellow, or red
topsoils need
nitrogen enrichment.
Fig. 4-27, p. 75
Leaf Litter Food Web
Connections: Matter Cycling in
Ecosystems
Biogeochemical cycles
Hydrologic cycle
(H2O)
Carbon Cycle
Nitrogen Cycle
Phosphorous Cycle
Sulfur Cycle
Back to Essential Questions
How Do Ecologists Learn About Ecosystems?
Field research - Ecologists do field research, observing and measuring the
ecosystem structure and function.
Remote sensing - New technologies such as remote sensing and geographic
information systems (GISs) gather data that is fed into computers for
analysis and manipulation of data. Computerized maps may be made of
an area to examine forest cover, water resources, air pollution emissions,
coastal changes, and changes in global sea temperatures.
Laboratory research - Ecologist use tanks, greenhouses, and controlled
indoor and outdoor chambers to study ecosystems
(laboratory research). This allows control of light, temperature, CO2,
humidity, and other variables.
Field and laboratory studies must be coupled together for a
more complete picture of an ecosystem.
Geographic Information System(GIS)
Tracking the 1997-1998 El Niňo
Topex / Poseidon
http://maps.google.com/maps?ie=UTF8&hl=en&tab=wl
Fig. 4-35 p. 84
Systems analysis develops
mathematical and other
models that simulate
ecosystems that are large
and very complex and can't
be adequately studied with
field and laboratory research.
This allows the analysis of
the effectiveness of various
alternate solutions to
environmental problems and
can help anticipate
environmental surprises.
We need baseline data about
components and physical and
chemical conditions in order
to determine how well the
ecosystem is functioning in
order to anticipate and
determine how best to
prevent harmful
environmental changes.
Define objectives
Systems
Measurement
Data
Analysis
Identify and inventory variables
Obtain baseline data on variables
Make statistical analysis of
relationships among variables
Determine significant interactions
System
Modeling
Construct mathematical model
describing interactions
among variables
System
Simulation
Run the model on a computer,
with values entered for
different variables
System
Optimization
Evaluate best ways to
achieve objectives