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Ecosystems
Chapter 30
Bye-Bye Bayou
• Louisiana’s coastal wetlands
are disappearing
• Global warming contributes
to wetland’s demise
• Sea levels rising worldwide
• Burning fossil fuels raises
global temperature
Impacts, Issues Video
Bye-Bye, Blue Bayou
Ecosystem
An array of organisms and their physical
environment, interconnected through a
one-way flow of energy and cycling
of raw materials
Modes of Nutrition
• Photoautotrophs
– Capture sunlight or chemical energy
– Primary producers
• Heterotrophs
– Extract energy from other organisms or
organic wastes
– Consumers, decomposers, detritivores
Simple
Ecosystem
Model
Energy
input from
sun
Producers
Autotrophs (plants and other
self-feeding organisms)
Nutrient
Cycling
Consumers
Heterotrophs (animals, most fungi,
many protists, many bacteria)
Energy output (mainly metabolic heat)
Simple Ecosystem Model
The role of organisms in an ecosystem
Consumers
• Herbivores
• Carnivores
• Parasites
SPRING
fruits
insects
rodents,
rabbits
birds
• Omnivores
• Decomposers
• Detritivores
SUMMER
fruits
rodents,
rabbits
insects
birds
seasonal variation in the diet of an
omnivore (red fox)
Trophic Levels
• Feeding relationships
– All organisms at a trophic level are the
same number of steps away from the
energy input into the system
• Autotrophs are producers
– closest to energy input
– first trophic level
Trophic Levels
Fourth-level consumers (heterotrophs):
5th Top carnivores, parasites,
detritivores, decomposers
4th
Third-level consumers (heterotrophs):
Carnivores, parasites, detritivores,
decomposers
Second-level consumers (heterotrophs):
3rd Carnivores, parasites, detritivores,
decomposers
First-level consumers (heterotrophs):
2nd
Herbivores, parasites, detritivores,
decomposers
Primary producers (autotrophs):
1st
Photoautotrophs, chemoautotrophs
marsh hawk
crow
garter snake
cutworm
flowering plants
fifth trophic level
top carnivore
(fourth-level consumer)
fourth trophic level
carnivore
(third-level consumer)
third trophic level
carnivore
(second-level consumer)
second trophic level
herbivore
(primary consumer)
first trophic level
autotroph
(primary producer)
Fig. 30-3, p.528
Food Chain
Food chain
Food Chain
• A straight-line
sequence of who
eats whom
• Simple food
chains are rare in
nature
marsh hawk
upland sandpiper
garter snake
cutworm
plants
marsh hawk
Higher
Trophic
Levels
Connections in a
tallgrass prairie food web
crow
upland
sandpiper
garter snake
frog
weasel
spider
Second
Trophic
Level
sparrow
earthworms, insects
First
Trophic
Level
badger coyote
prairie vole
pocket gopher
ground squirrel
grasses, composites
Fig. 30-4, p.529
Rain Forest
Rain-forest food web
Energy Losses
• Energy transfers are never 100%
efficient
• Some energy is lost at each step
• Limits number of trophic levels in an
ecosystem
Biological Magnification
Nondegradable or slowly degradable
substances become more and more
concentrated in tissues of organisms at
higher trophic levels of a food web
DDT in Food Webs
• Synthetic pesticide banned
in United States since
1970s
• Carnivorous birds
accumulate DDT in their
tissues, produce brittle egg
shells
Fig. 30-5, p.530
Ecological Pyramids
• Primary producers are bases for
successive tiers of consumers
• Biomass pyramid
– Dry weight of all organisms
• Energy pyramid
– Usable energy decreases as it is
transferred through ecosystem
Biomass Pyramid
• Aquatic ecosystem, Silver Springs, Florida
• Long-term study of a grazing food web
decomposers,
detritivores
(bacteria,
crayfish)
5
1.5
third-level carnivores
(gar, large-mouth bass)
1.1
second-level consumers
(fishes, invertebrates)
37
first-level consumers
(herbivorous fishes,
turtles, invertebrates)
809
primary producers (algae,
eelgrass, rooted plants)
Energy Pyramid
• Primary producers trapped about 1.2% of
the solar energy that entered the
ecosystem
• 6–16% passed on to next level
21
top carnivores
decomposers + detritivores = 5,080
carnivores
herbivores
383
3,368
producers
20,810 kilocalories/square meter/year
Silver Springs Study
Energy flow at Silver Springs
Biogeochemical Cycle
• Flow of an essential substance from the
environment to living organisms and
back to the environment
• Main reservoir is in the environment
• Geologic processes, decomposers aid
cycles
Three Categories
• Hydrologic cycle
– Water
• Atmospheric cycles
– Nitrogen and carbon
• Sedimentary cycles
– Phosphorus and other
nutrients
Hydrologic Cycle
atmosphere
wind-driven water vapor
40,000
evaporation precipitation
from ocean into ocean
425,000
385,000
precipitation
onto land
111,000
evaporation from land
plants (evapotranspiration)
71,000
surface and
groundwater
flow 40,000
ocean
land
Hydrologic Cycle
Hydrologic cycle
Global Water Crisis
• Limited amount of fresh water
• Desalinization is expensive and requires
large amounts of energy
• Aquifers are being depleted
• Groundwater is contaminated
• Sewage, agricultural runoff, and industrial
chemicals pollute rivers
Aquifer Problems
Threats to aquifers
Carbon Cycle
• Carbon moves through atmosphere,
food webs, ocean, sediments, and rocks
• Sediments and rocks are the
main reservoir
• Combustion of fossil fuels changes
natural balance
Carbon Cycle
Carbon cycle
Greenhouse Effect
• Greenhouse gases impede escape of
heat from Earth’s surface
Greenhouse Effect
Greenhouse effect
Global Warming
Long-term increase in temperature of
Earth’s lower atmosphere
Greenhouse Gases
Carbon dioxide and temperature
Carbon Dioxide Increase
• Carbon dioxide levels fluctuate
seasonally
• Average level is steadily increasing
• Burning of fossil fuels and deforestation
are contributing to the increase
Other Greenhouse Gases
• CFCs: synthetic gases used in plastics
and in refrigeration
• Methane: released by natural gas
production, livestock
• Nitrous oxide: released by bacteria,
fertilizers, and animal wastes
Greenhouse Gases
Greenhouse gases
Table 30-1, p.537
Nitrogen Cycle
• Nitrogen is used in amino acids and
nucleic acids
• Main reservoir is nitrogen gas in the
atmosphere
• Nitrogen gas can’t enter food web
Nitrogen Cycle
Nitrogen cycle
Human Effects
• Humans increase rate of nitrogen loss
by clearing forests and grasslands
• Humans increase nitrogen in water and
air by using fertilizers and by burning
fossil fuels
• Too much or too little nitrogen can
compromise plant health
Air Pollution
• Effects of nitrogen oxides released by
burning fossil fuels
Deforestation
Effect of air pollution in forests
Phosphorus Cycle
• Phosphorus is part of phospholipids,
nucleotides, NADH, ATP
• Main limiting factor in ecosystems
• Reservoir is Earth’s crust; no gaseous
phase
Phosphorus Cycle
Phosphorus cycle
Human Effects
• In tropical countries, clearing lands for
agriculture may deplete phosphoruspoor soils
• In developed countries, fertilizer
causes phosphorus overloads in soil
Eutrophication
• Phosphorus is limiting factor in many
freshwater ecosystems
• Runoff from phosphate fertilizers
accelerates algal growth in waterways
• Resulting dense algal blooms cause
system overload and death
Clouds Move
Stream