Environmental Science: Toward a
Sustainable Future
Richard T. Wright
Chapter 2
Ecosystems: What They Are
PPT by Clark E. Adams
The Organization of Ecosystems




A description of ecosystems
The structure of ecosystems
The relationship between ecosystems and biomes
Human impacts on ecosystem structure
Ecosystem Types in the United States






Coasts and oceans
Farmlands
Forests
Fresh waters
Grasslands and shrub lands
Urban and suburban areas
Ecosystems: A Description




Biotic communities: grouping or assemblage of
plants, animals, and microbes
Species: different kinds of plants, animals, and
microbes in the community
Populations: number of individuals that make up
the interbreeding, reproducing group
Associations: how a biotic community fits into the
landscape
How Ecosystems Are Formed
Abiotics (moisture and temperature)
predict
Plants (+ moisture = forest)
(temperature = forest type)
predict
Animals (lynx or bobcat)
Ecosystems

A grouping of plants, animals, and microbes
occupying an explicit unit of space and interacting
with each other and their environment
Ecotone: transitional region between different
ecosystems


Shares many of the
species and characteristics
of both ecosystems
May also include unique
conditions that support
distinctive plant and animal
species
Ecotone: transitional region between different
ecosystems


Shares many of the
species and characteristics
of both ecosystems
May also include unique
conditions that support
distinctive plant and animal
species
Topics on Ecosystem Structure




Trophic categories
Trophic relationships: food chains, food webs,
trophic levels
Nonfeeding relationships: symbiosis
Abiotic factors
Autotrophs = Producers = Self feeders
Inorganic and Organic

Inorganic
 Oxygen
 Carbon dioxide
 Nitrogen
 Water
 pH

Organic
 All living things
 Products of living
things
Consumers = Heterotrophs




Primary consumers = herbivores = rabbits: eat
plant material
Secondary consumers = carnivores = predators =
coyotes: prey are herbivores and other animals
Parasites = predator = either plant or animal: prey
are plants or animals
Detritus feeders and decomposers = bacteria and
fungi: prey are plants or animals
Trophic Categories
Trophic Levels: Food Chain
Third-order Consumer
Secondary Consumer
Primary Consumer
Producer
Match Organisms with Trophic Level(s)
Trophic Levels
Organisms
Secondary
Consumer
ThirdOrder
Consumer
Snakes
X
X
Owls
X
X
X
X
Plants
Producer
X
Rabbits
Bacteria
Primary
Consumer
X
X
X
Match Organisms with Trophic Level(s)
Trophic Levels
Organisms
Producer
Autotrophs
X
Herbivores
Primary
Consumer
Secondary
Consumer
Third-Order
Consumer
X
X
X
Carnivores
Omnivores
X
X
X
Parasites
X
X
X
Trophic Relationships among Producers and
Consumers
Food Webs
Trophic Level Energy Flow
Third-order Consumer 1 Kcal
- 10x
Secondary Consumer 10 Kcal
- 10x
Primary Consumer 100 Kcal
- 100x
Producer 10,000 Kcal
Trophic Levels: Pyramid of Biomass
5
4
3
2
1
Which level is occupied by:
producers?
primary consumers?
secondary consumers?
third-order consumers?
Trophic Levels: Pyramid of Energy
5
4
3
2
1
Which level is occupied by:
producers?
primary consumers?
secondary consumers?
third-order consumers?
Symbiosis: Living Together


+ and + = Mutualism. Both species benefit by the
interaction between the two species: yucca plant and
Pronuba moth
+ and 0 = Commensalism. One species benefits from
the interaction and the other is unaffected: remora fish
and shark
Symbiosis: Living Together


+ and – = One species benefits from the interaction and
the other is adversely affected. Examples are
predation, parasitism, and disease.
– and – = Competition. Both species are adversely
affected by the interaction.
Resource Partitioning
Law of Limiting Factors
Application of the Law of Limiting Factors

Compare the “tolerance” differences for a trout and
a catfish using water:



temperature (cold or warm).
oxygen concentration (high or low).
salinity (high or low).
From Ecosystems to Global Biomes




The role of climate
Microclimate and other abiotic factors
Biotic factors
Physical barriers
Climate and Major Biomes
Identify Biomes A to E Based on Temperature
and Precipitation Levels: Answers on Next Slide
High
A
D
C
B
Low
E
Precipitation
High
Answers to Previous Slide





A has high temperature and low moisture = hot
desert
B has low temperature and low moisture = cold
desert (tundra with permafrost)
C has medium temperatures and moisture =
grassland
D has high temperature and moisture = rain forest
E has low temperature and high precipitation =
arctic poles
Abiotic Effects of Latitude and Altitude
The Human Factor

Three revolutions



Neolithic
Industrial
Environmental
How Humans Modify Their Physical
Environments to Meet Their Needs





Produce abundant food
Control water flow rate and direction
Overcome predation and disease
Construct our own ecosystems
Overcome competition with other species
End of Chapter 2