Transcript Plants and Pollinators

Ecosystems
Chapter 28
Ecosystems
• Chapter 28
Fig. 41-1, p.730
Ecosystem
An association of organisms and their
physical environment, interconnected by
ongoing flow of energy and a cycling of
materials
Modes of Nutrition
• Autotrophs
– Capture sunlight or chemical energy
– Producers
• Heterotrophs
– Extract energy from other organisms or
organic wastes
– Consumers, decomposers, detritivores
Simple
Ecosystem
Model
Autotrophs (plants,
other selffeeding organisms)
Heterotrophs
(animals, most
fungi,
many protists,
many bacteria)
(mainly metabolic heat)
Consumers
1. Herbivores
2. Carnivores
3. Parasites
4. Omnivores
5. Decomposers
6. Detritivores
Omnivores, Red Fox
Diet fluctuations due to Seasonal variation in diet
SPRING
fruits
rodents,
insects
rabbits
birds
fruits
SUMMER
rodents,
insects
rabbits birds
fruits
FALL
rodents,
insects
rabbits birds
fruits insects
WINTER
rodents,
rabbits
birds
Trophic Levels
• All the organisms at a trophic level are
the same number of steps away from
the energy input into the system
• Producers are closest to the energy
input and are the first trophic level
Trophic Levels in Prairie
Fourth-level consumers (heterotrophs):
5th
Top carnivores, parasites,
detritivores, decomposers
Third-level consumers (heterotrophs):
4th
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
Food Chain
marsh hawk
• A straight line
sequence of who
upland sandpiper
eats whom
• Simple food chains
garter snake
are rare in nature
cutworm
flowering plant
Food Web
marsh hawk
HIGHER
TROPHIC
LEVELS
Complex array of
carnivores,
omnivores and
other consumers.
Many feed at
more than one
trophic level
continually,
seasonally, or
when an
oppportunity
presents itself
upland
sandpiper
crow
garter snake
frog
spider
badger
weasel
SECOND TROPHIC
LEVEL Primary
consumers (e.g.,
herbivores,
detritivores, and
decomposers)
coyote
clay-colored
sparrow
earthworms, insects (e.g.,
grasshoppers, cutworms)
prairie vole
pocket
gopher
ground squirrel
FIRST TROPHIC LEVEL
Primary producers
grasses, composites
Energy Losses
• Energy transfers are never 100 percent
efficient
• Some energy is lost at each step
• Limits the number of trophic levels in an
ecosystem
Energy Losses
The mouse receives energy from the food it eats.
•
Cells extract the food's energy for growth, acquiring food, escaping enemies lost as heat.
•
Some of the energy that is in the food is lost in the mouse's waste (feces).
•
The remaining energy is stored in the mouse's body and is available to the organism that
preys on it.
•
About 90% of the energy is used or lost, only 10% is available to predators.
Grazing Food Web
Detrital Food Web
Two Types of Food Webs
Producers
(photosynthesizers)
Producers
(photosynthesizers)
herbivores
decomposers
carnivores
detritivores
decomposers
ENERGY OUTPUT
ENERGY OUTPUT
Biological Magnification
A nondegradable or slowly degradable substance becomes
more and more concentrated in the tissues of organisms at
higher trophic levels of a food web
* Dichloro-Diphenyl-Trichloroethane (DDT)
* Polychlorinated biphenyls (PCBs)
DDT in Food Webs
• Synthetic pesticide
banned in the United
States since the 1970s
• Birds that were top
carnivores
accumulated DDT in
their tissues
DDT
PCBs in Food Webs
• PCB concentrations in animal
tissue can be magnified up to
25 million times.
• Microscopic organisms pick up
chemicals from sediments
• Consumed in large numbers by
filter feeding zooplankton.
• Mysid shrimp then consume
zooplankton
• fish eat the mysid
• and so on up the food web to
the herring gull.
• (Figure and caption from Our
Stolen Future, p. 27)
DDT Detection
• In 1962, Rachel Carson,
a former U.S. Fish and
Wildlife Service (USFWS)
scientist and writer,
published Silent Spring,
outlining the dangers of
DDT
Fig. 41-8, p.736
DDT in Food Webs
• Heinz Meng
• Responsible for the
reintroduction of the
Peregrine Falcon.
DDT residues
• Why was there
never a concern for
the Ring-billed
gulls?
Fig. 41-7, p.736
Primary Productivity
• Gross primary productivity is
ecosystem’s total rate of photosynthesis
• Net primary productivity is rate at which
producers store energy in tissues in
excess of their aerobic respiration
Primary Productivity Varies
• Seasonal variation
• Variation by habitat
• The harsher the environment, the
slower plant growth, the lower the
primary productivity
Biomass Pyramid (energy)
• Aquatic ecosystem in Florida
• Site of a long-term study of a grazing food web
1.5
11
37
5
third-level carnivores
(gar, large-mouth bass)
second-level consumers
(fishes, invertebrates)
first-level consumers
(herbivorous fishes,
turtles, invertebrates)
809
decomposers, detritivores
(bacteria, crayfish)
primary producers (algae,
eelgrass, rooted plants)
Silver Springs:
Annual Energy
Flow
ENERGY INPUT
17,000,000
kilocalories
incoming solar energy
not harnessed:
energy transfers
through ecosystem
1,679,190
(98.8%)
20,810
(1.2%)
producers
energy still
in organic
wastes and
remains:
transferred to
the next
trophic level:
3,368 13,197
4,245
energy
losses as
metabolic
heat and as
net export
from the
ecosystem:
herbivores
383
720
carnivores
21
90
2,265
272
top carnivores
5
16
decomposers,
detritivores
5,060
ENERGY OUPUT:
20,810 + 1,679,190
TOTAL ANNUAL ENERGY FLOW:
1,700,000 (100%)
Pyramid of Energy Flow
• Primary producers trapped about 1.2
percent of the solar energy that entered
the ecosystem
• 6-16% passed on to next level
top carnivores
21
carnivores
herbivores
383
3,368
producers
20,810
decomposers + detritivores = 5,060
Primary Productivity
Although average productivity per unit surface area is
lower than on land, Total productivity on land and in
seas is about equal..Due to amount of water
coverage. (Red high Purple lowest)
All Heat in the End
• At each trophic level, the bulk of the
energy received from the previous level
is used in metabolism
• This energy is released as heat energy
and lost to the ecosystem
• Eventually, all energy is released as
heat
Biogeochemical Cycle
• The flow of a nutrient from the
environment to living organisms and
back to the environment
• Main reservoir for the nutrient is in the
environment
Nutrient Flow:
Land Ecosystem
Three Categories
1. Hydrologic cycle
– Water
2. Atmospheric cycles
– Nitrogen and carbon
3. Sedimentary cycles
– Phosphorus and sulfur
Hydrologic Cycle
Atmosphere
wind-driven water vapor
40,000
evaporation
from ocean
425,000
precipitation
into ocean
385,000
precipitation
onto land
111,000
evaporation from land
plants
(evapotranspiration)
71,000
surface and
groundwater flow
40,000
Oceans
Land
Hubbard Brook Experiment
• A watershed was experimentally
stripped of vegetation
• All surface water draining from
watershed was measured
• Removal of vegetation caused a six-fold
increase in the calcium content of the
runoff water
Hubbard Brook Experiment
losses from
disturbed
watershed plot
time of
deforestation
Aquifer Depletion
• Green signifies high
overdrafts
• Gold, moderate
overdrafts
• Yellow, insignificant
withdrawals
• Shaded areas show
groundwater pollution
• Blue squares: saltwater
intrusion
Carbon Cycle
• Carbon moves through the atmosphere
and food webs on its way to and from
the ocean, sediments, and rocks
• Sediments and rocks are the main
reservoir
Carbon Cycle
diffusion
Atmosphere
Bicarbonate,
volcanic action
carbonate
Marine
food
TERRESTRIAL
webs ROCKS
Terrestrial
rocks
photosynthesis
Land food
webs
Soil water
Marine Sediments
weathering
Peat, fossil
fuels
Carbon in the Oceans
• Most carbon in the ocean is dissolved
carbonate and bicarbonate
• Ocean currents carry dissolved carbon
Carbon in Atmosphere
• Atmospheric carbon is mainly carbon
dioxide
• Carbon dioxide is added to
atmosphere
– Aerobic respiration, volcanic action,
burning fossil fuels
• Removed by photosynthesis
Greenhouse Effect
• Greenhouse gases impede the escape
of heat from Earth’s surface
Carbon Dioxide Increase
• Carbon dioxide levels fluctuate
seasonally
• The average level is steadily increasing
• Burning of fossil fuels and deforestation
are contributing to the increase
Carbon Dioxide Increase
Other Greenhouse Gases
• CFCs - synthetic gases used in plastics
and in refrigeration
• Methane - produced by termites and
bacteria
• Nitrous oxide - released by bacteria,
fertilizers, and animal wastes
Greenhouse Gases
carbon
dioxide
methane
CFCs
nitrous oxide
Global Warming
• Long-term increase in the temperature
of Earth’s lower atmosphere
Nitrogen Cycle
• Nitrogen is used in amino acids and
nucleic acids
• Main reservoir is nitrogen gas in the
atmosphere
Nitrogen Cycle
gaseous nitrogen in atmosphere
food webs on land
nitrogen fixation
fertilizers
uptake by autotrophs
ammonia, ammonium in soil
excretion, death,
decomposition
nitrogen-rich wastes,
remains in soil
ammonification
loss by
leaching
nitrification
uptake by autotrophs
loss by
dentrification
nitrate in soil
nitrification
nitrate in soil
loss by leaching
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
Ammonification & Nitrification
• Bacteria and fungi carry out
ammonification, conversion of
nitrogenous wastes to ammonia
• Nitrifying bacteria convert ammonium to
nitrites and nitrates
Nitrogen Loss
• Nitrogen is often a limiting factor in
ecosystems
• Nitrogen is lost from soils via leaching
and runoff
• Denitrifying bacteria convert nitrates
and nitrites to nitrogen gas
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
Phosphorus Cycle
• Phosphorus is part of phospholipids and
all nucleotides
• It is the most prevalent limiting factor in
ecosystems
• Main reservoir is Earth’s crust; no
gaseous phase
Phosphorus Cycle
mining
excretion
FERTILIZER
GUANO
agriculture
uptake by
autotrophs
MARINE
FOOD
WEBS
weathering
DISSOLVED
IN OCEAN
WATER
uptake by
autotrophs
weathering
DISSOLVED IN
SOILWATER,
LAKES, RIVERS
death,
decomposition
sedimentation
death,
decomposition
leaching, runoff
setting out
uplifting over
geologic time
MARINE SEDIMENTS
ROCKS
LAND
FOOD
WEBS
Phosphorus Cycle
• If too much fertilizer is
added to the soil what is not
absorbed by plants leaches
into to local water ways.
• This leads to the eutrification
of rivers, ponds and lakes.
• The process in which oxygen
is removed from the water by
the decomposition of large
amounts of organic matter
Human Effects
• In tropical countries, clearing lands for
agriculture may deplete phosphorus-
poor soils
• In developed countries, phosphorus
runoff is causing eutrophication of
waterways