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Ecosystems
Chapter 30
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
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
Tall-Grass Prairie Food Web
marsh hawk
sandpiper
crow
snake
frog
weasel
badger
coyote
spider
sparrow
earthworms, insects
vole
pocket
gopher
grasses, composites
ground
squirrel
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
Which statement about ecosystems is false?
1.
2.
3.
4.
energy flows in a cycle
between producers and
consumers
nutrients are recycled by
passing from producers to
consumers and back again
via decomposers
in most ecosystems, energy
flow begins with the capture
of solar energy by
photosynthesizers
heterotrophs include bacteria
and fungi
25%
1
25%
2
25%
3
25%
4
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
Grazing
Food Web
Detrital
Food Web
Two Types of Food Webs
Energy Input:
Energy Input:
Transfers:
Transfers:
Producers
(photosynthesizers)
Producers
(photosynthesizers)
energy
in organic
wastes,
remains
herbivores
carnivores
energy
losses
as metabolic
heat
and as net
export
from
ecosystem
energy
in organic
wastes,
remains
detritivores
detritivores
decomposers
Energy
Output
decomposers
decomposers
Energy
Output
energy
losses
as metabolic
heat
and as net
export
from
ecosystem
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
Watershed
• A region where
precipitation is
funneled into a
single stream
or river
Hubbard Brook Experiment
• A watershed was experimentally
stripped of vegetation
• All surface water draining from
watershed was measured
• Deforestation caused six-fold increase
in calcium content of runoff water
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 Depletion
Hawaiian
Islands
Alaska
When the Earth's waters move from ocean to
atmosphere to land and back again, it is called the
_____ cycle.
25%
25%
25%
25%
1. water
2. hydrologic
3. hydrodynamic
4. precipitation
1
2
3
4
A watershed is _____.
1.
a stream or river
2.
a river that discharges
water directly into the
ocean
3.
a region where
precipitation becomes
funneled into a single
stream or river
4.
a region where
precipitation becomes
funneled into a reservoir
for use in human
communities
25%
1
25%
2
25%
3
25%
4
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
diffusion between
atmosphere and ocean
bicarbonate and
carbonate in
ocean water
photosynthesis
combustion of fossil fuels
aerobic
respiration
marine food
webs
death,
incorporation sedimentation
into sediments
uplifting
sedimentation
marine sediments
Carbon Cycle: Marine
atmosphere
combustion of
fossil fuels
volcanic action
terrestrial
rocks
weathering
photosynthesis
aerobic combustion
respiration of wood
deforestation
land food
webs
soil water
leaching,
runoff
death, burial,
compaction over
geologic time
Carbon Cycle: Land
peat,
fossil
fuels
My Carbon Cycle
1. I eat carbohydrate molecules.
– These are molecules of fuel which I will
“burn”.
– Some of the energy released when I burn
them will be trapped for me to use. The
rest will be lost as heat.
2. The waste products of burned fuel
are carbon dioxide and water. I
breathe these out.
3. Plants (or other producers) take in
carbon dioxide from the atmosphere
and use it to make carbohydrate.
According to the last slide, why do I
eat carbohydrates?
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25% 25% 25% 25%
B
1. Because they
taste good.
2. Because they
contain lots of
vitamins.
3. Because they
contain lots of
energy.
4. Because they are
low in calories.
Energy saved from burning up my
fuel is saved in the form of :
25%
H
ea
t
t
25%
Fa
25%
TP
us
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25%
A
Muscle
ATP
Fat
Heat
M
1.
2.
3.
4.
The only reason I need to breathe in
oxygen is :
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=
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.
25% 25% 25% 25%
In
1. I need oxygen to
“burn” fuel
molecules.
2. All living things
need oxygen.
3. Oxygen + carbon
= carbon dioxide.
4. Oxygen is
corrosive.
Breathing out :
th
e
of
r id
et
s
G
...
w
as
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.
25% 25% 25% 25%
H
1. Helps me regulate
my body
temperature.
2. Gets rid of excess
fuel molecules.
3. Burns extra
calories.
4. Gets rid of the
waste products of
burned fuel.
The carbon in the plants I eat comes
from :
The atmosphere.
The food they eat.
The soil.
Water.
fo
od
e
Th
r.
at
e
so
e
Th
W
.
th
ey
ea
t
re
.
he
os
p
at
m
e
il.
25% 25% 25% 25%
Th
1.
2.
3.
4.
The carbon in the steak I eat comes
from :
1. Supplements in
animal feed.
2. Vitamins.
3. The cow’s
drinking water.
4. The plants eaten
by the cow.
Th
n
ts
e
pl
an
w
’s
ea
te
dr
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ki
ng
by
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.
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..
25% 25% 25% 25%
Greenhouse Effect
• Greenhouse gases impede escape of
heat from Earth’s surface
Global Warming
Long-term increase in temperature of
Earth’s lower atmosphere
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 Increasing
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
Fig. 30-16, p.538
Nitrogen Fixation
• Plants cannot use nitrogen gas
• Nitrogen-fixing bacteria convert
nitrogen gas into ammonia (NH3)
• Ammonia and ammonium can be
taken up by plants
Air Pollution
• Effects of nitrogen oxides released by
burning fossil fuels