Ecosystems: What Are They and How
Do They Work?
G. Tyler Miller’s
Living in the Environment
14th Edition
Chapter 4
Key Concepts
Basic ecological principles
Major components of ecosystems
Matter cycles and energy flow
Ecosystem studies
Principles of Sustainability
The Nature of Ecology
•
•
•
Oilos “place to live” and logos “study of”
The study of how organisms interact with
each other and their environment.
Organism: any form of life.
Cell types: Eukaryotic = membrane bound
nucleus, Prokaryotic = first cell no
membrane bound nucleus.
Microbes: invisible rulers of the
earth
• Mostly Prokaryotes but some Eukaryotes.
• Microbes are ubiquitous… that means
EVERYWHERE.
• Billions in your body, on your skin, in the soil…
EVERYWHERE.
• Bacteria (prokaryotes), protozoan, fungi, etc. Most
are too small for us to see.
• Bad things microbes are usually known for:
infectious disease, fungal infections, malaria.
• Good things: vital role in producing many foods:
bread,cheese, yogurt, vinegar, sauerkraut, beer.
Microbes: invisible rulers of the
earth
• Bacteria the “fix” nitrogen needed for protein
production.
• Decompose waste… think of all of the dead
things that would still be around without
decomposition.
• Digest your food, provide nutrients, some
antibiotics are microbes.
• Control disease… take care of “bad” bacteria.
The Nature of Ecology
Ecosystem organization
Organisms
Populations
Communities
Ecosystems
Biosphere
Fig. 4-2 p. 57
Organism
• Organism: any form of life..
• Cell is basic unit of life
– Eukaryotic Cell: membrane bound organelles w/ nucleus.
Protists, fungi, plants, animals,
– Prokaryotic Cell: no distinct nucleus. Bacteria
• Species: group of organisms with similar appearance,
behavior, chemistry and genetic makeup. Produce
fertile offspring.
– Asexual reproduction: binary fission, budding
– Sexual: combine haploid gametes to produce offspring.
Population
• Group of interacting individuals of the same
species.
• Populations respond to changes in
environment: 1. Size. 2. Age distribution. 3.
Density. 4. Genetic composition.
• Communities: Complex interacting
populations.. Including plants, animals, fungi,
protists, and bacteria.
• Ecosystem: all biotic and abiotic components
are interacting
– Communities of different species interacting with
one another and their non-living environment.
– Range in size from a puddle to entire forest. Define
the “system.”
• Biosphere: all of the earth’s interacting
ecosystems.
The Earth’s Life-Support Systems
Troposphere
Stratosphere
Hydrosphere
Lithosphere
Biosphere
Fig. 4-7 p. 60
Major Parts of Earth’s Life Support
• Atmosphere: thin envelope of air around the
planet.
– Troposphere: inner layer about 17 kilometers
above sea level.
– Stratosphere: 17-48 kilometers. Lower portion
contains enough ozone O3 to filter most of the
Sun’s harmful Ultraviolet radiation.
• Hydrosphere: Earth’s liquid water (surface and
underground), ice (polar, icebergs), and ice
frozen in the soil, and water vapor in the
atmosphere.
Major Parts of Earth’s Life Support
• Lithosphere: Earth’s crust and upper mantle
– Contains nonrenewable fossil fuels and minerals
– Contains renewable soil nutrients needed for plant
life.
• Biosphere: portion of Earth where living
(biotic) organisms exist and interact with one
another.
– Includes most of the hydrosphere, lower parts of
the atmosphere, and the upper lithosphere.
– Reaches from the deepest ocean floor to the tops of
the highest mountains.
Goal of Ecology is to understand the
interactions in this thin, lifesupporting global skin or membrane
of air, water, soil, and organisms.
Natural Capital: Sustaining Life of
Earth
 One-way flow
of energy from Sun
Through livingorganisms
 Cycling of
Crucial Elements
 Atoms, ions, molecules
through the biosphere.
 Gravity allows the Earth
to hold on to the atomosphere
and causes downward
movement of chemicals in
matter cycles.
Fig. 4-8 p. 60
Solar Capital: Flow of Energy to and
from the Earth
•Lights and warms the planet
•Supports photosynthesis
•Powers the cycling of matter
•Drive the climate and weather systems that distribute heat and freshwater.
•Gigantic fireball of hydrogen and helium.
•Temperatures and pressures in its inner core cause fusion of hydrogen releasing
enormous amounts of energy.
Fig. 4-9 p. 61
Giant Thermonuclear Reactor
• Radiates in all directions
• Radiation moves at the
speed of light (EMS) and
makes the 150 million
kilometer (93 million
miles) trip in slightly more
than 8 minutes.
• What happens to the solar
radiation?
• 1 billionth received by
Earth.
• Most energy reflected or
absorbed by chemicals in
the atmosphere.
Natural Capital: Major Biomes
 Biomes
 Role of
climate
 Aquatic
life zones
Fig. 4-10 p. 62
Components of Ecosystems

Abiotic chemicals

Photosynthesis:removes CO and water



and adds Oxygen and glucose 6H2O + 6CO2
+ energy C6H12O6 + 6O2
Producers (autotrophs)
Consumers (heterotrophs)
Aerobic
cellular respiration


C6H12O6 + 6O2 6H2O + 6CO2 + energy
Decomposers
Fig. 4-17 p. 67
Ecosystem Factors
Abiotic factors Range of tolerance
Limiting factors
Biotic factors
Fig. 4-13 p. 64
Range of Tolerance
• Law of Tolerance: The distribution of a
species in an ecosystem is determined by the
levels of one or more physical or chemical
factors.
• Tolerance Limits: too much or too little of any
abiotic factor can limit or prevent growth of a
populations, even if all other factors are at or
near an optimum range of tolerance.
Respiration: Getting Energy
• Producers & Consumers use chemical energy
stored in glucose and other organic
compounds to fuel life processes.
• Aerobic Respiration: uses oxygen to convert
organic nutrients back into carbon dioxide and
water.
• C6H12O6+ O2  CO2 + H2O + energy
• Anaerobic respiration (fermentation): releasing
of energy w/out oxygen.
Biodiversity: the amazing variety of earth’s genes, species,
ecosystems, and ecosystem processes.
 Genetic diversity: variety in genetic make-up among
individuals in a species
 Species diversity: Variety among species or distinct types of
living organisms.
 Ecological diversity: Variety of forests, deserts, grasslands,
streams, lakes, oceans, coral reefs, wetlands, and other biological
communities.
 Functional diversity: Biological and chemical processes or
functions such as energy flow and matter cycling needed for the
survival of species and biological communities.
Connections: Energy Flow in
Ecosystems
 Food chains: sequence of organisms each of which is a
food source for the next.
 Trophic Levels: feeding step.. Producers are the first
level always.
 Food webs: complex network of interconnected food
chains … most species participate in several different
food chains.
Trophic Levels
Autotroph (producer): first trophic level
Primary consumer (herbivore): second trophic level
Secondary consumer (carnivore): third trophic level
Tertiary consumer: fourth trophic level
 Omnivore eats producers and consumers.
 Detritivores and scavengers: all trophic levels… they do not care.
 Decomposers
Connections: Food Webs and Energy
Flow in Ecosystems
Food chains
Food webs
Fig. 4-18 p. 77; Refer to Fig. 4-19 p. 78
Human
Blue whale
Sperm whale
Killer
whale
Elephant
seal
Crabeater seal
Leopard
seal
Emperor
penguin
Adélie
penguins
Petrel
Squid
Fish
Carnivorous plankton
Herbivorous
zooplankton
Krill
Phytoplankton
Figur
Ecological Pyramids
 Pyramid of
energy flow
 Ecological
efficiency
 Pyramid of
biomass
 Pyramid of
numbers
Fig. 4-21 p. 70
Primary Productivity of Ecosystems

Gross primary productivity (GPP): rate at which an ecosystem’s producers convert
solar energy into chemical energy.

Net primary productivity (NPP): Producers need energy to survive. What is
left or available for use as food b other organisms in an ecosystem.
Fig. 4-25 p. 81
73%
Not used by humans
It is estimated that humans
use, waste, or destroy about 1.
27% of the earth’s total NPP
and about 2. 40% of the
earth’s NPP of terrestrial
systems. What will happen
when population doubles in
the next 40-50 years?
3%
Used directly
8%
Lost or degraded land
16%
Altered by human activity
Figur
Soil Profiles in Different Biomes
Fig. 4-27, p. 75
Soils
Origins
Importance
Maturity and Horizons
Variations with Climate and Biomes
Variations in Texture and Porosity
Connections: Matter Cycling in
Ecosystems
 Biogeochemical cycles
 Hydrologic cycle (H2O)
 Carbon cycle
 Nitrogen cycle
 Phosphorus cycle
 Sulfur cycle
Hydrologic (Water) Cycle
Fig. 4-28 p. 76
Condensation
Rain clouds
Transpiration
Transpiration
from plants
Precipitation to
land
Precipitation
Runoff
Surface runoff
(rapid)
Evaporation
Precipitation
Evaporation
from land
Evaporation
from ocean
Precipitation to
ocean
Surface
runoff
(rapid)
Infiltration and
Percolation
Groundwater movement (slow)
Ocean storage
Hydrological Cycle
The Carbon Cycle (Marine)
Fig. 4-29, p. 78
The Carbon Cycle (Terrestrial)
Fig. 4-29, p. 79
The Nitrogen Cycle
Fig. 4-31 p. 80
The Phosphorus Cycle
Fig. 4-33 p. 82
The Sulfur
Cycle
Fig. 4-34 p. 83
How Do Ecologists Learn About
Ecosystems?
Field research
Remote sensing
Geographic information systems (GIS)
Laboratory research
Systems analysis
Geographic Information System
(GIS)
Fig. 4-35 p. 84
Systems Analysis
Fig. 4-36 p. 85