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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

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ecosystems

Ecosystems

Chapter 28

slide2

Ecosystems

  • Chapter 28

Fig. 41-1, p.730

ecosystem
Ecosystem

An association of organisms and their physical environment, interconnected by ongoing flow of energy and a cycling of materials

modes of nutrition
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
Simple Ecosystem Model

Autotrophs (plants, other self-feeding organisms)

Heterotrophs (animals, most fungi, many protists, many bacteria)

(mainly metabolic heat)

consumers
Consumers
  • Herbivores
  • Carnivores
  • Parasites
  • Omnivores
  • Decomposers
  • Detritivores
omnivores red fox diet fluctuations due to seasonal variation in diet
Omnivores, Red FoxDiet fluctuations due to Seasonal variation in diet

fruits

rodents, rabbits

insects

SPRING

birds

fruits

rodents, rabbits

insects

SUMMER

birds

fruits

rodents, rabbits

insects

FALL

birds

fruits

insects

rodents, rabbits

birds

WINTER

trophic levels
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
Trophic Levels in Prairie

Fourth-level consumers (heterotrophs):

Top carnivores, parasites, detritivores, decomposers

5th

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
Food Chain

marsh hawk

  • A straight line sequence of who eats whom
  • Simple food chains are rare in nature

upland sandpiper

garter snake

cutworm

flowering plant

energy losses
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 losses13
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.
two types of food webs

Grazing Food Web

Detrital Food Web

Two Types of Food Webs

Producers (photosynthesizers)

Producers (photosynthesizers)

decomposers

herbivores

carnivores

detritivores

decomposers

ENERGY OUTPUT

ENERGY OUTPUT

biological magnification
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
DDT in Food Webs
  • Synthetic pesticide banned in the United States since the 1970s
  • Birds that were top carnivores accumulated DDT in their tissues
pcbs in food webs
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
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 webs20
DDT in Food Webs
  • Heinz Meng
  • Responsible for the reintroduction of the Peregrine Falcon.
ddt residues
DDT residues
  • Why was there never a concern for the Ring-billed gulls?

Fig. 41-7, p.736

primary productivity
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
Primary Productivity Varies
  • Seasonal variation
  • Variation by habitat
  • The harsher the environment, the slower plant growth, the lower the primary productivity
biomass pyramid energy
Biomass Pyramid (energy)
  • Aquatic ecosystem in Florida
  • Site of a long-term study of a grazing food web

third-level carnivores

(gar, large-mouth bass)

1.5

second-level consumers

(fishes, invertebrates)

11

first-level consumers

(herbivorous fishes,

turtles, invertebrates)

37

5

primary producers (algae,

eelgrass, rooted plants)

809

decomposers, detritivores

(bacteria, crayfish)

silver springs annual energy flow

ENERGY INPUT

Silver Springs: Annual Energy Flow

17,000,000 kilocalories

incoming solar energy not harnessed:

energy transfers through ecosystem

1,679,190 (98.8%)

20,810 (1.2%)

producers

energy losses as metabolic heat and as net export from the ecosystem:

transferred to the next trophic level:

energy still in organic wastes and remains:

3,368

4,245

13,197

herbivores

383

720

2,265

carnivores

21

272

90

top carnivores

5

16

decomposers, detritivores

5,060

20,810 + 1,679,190

ENERGY OUPUT:

TOTAL ANNUAL ENERGY FLOW:

1,700,000 (100%)

pyramid of energy flow
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

decomposers + detritivores = 5,060

21

carnivores

herbivores

383

3,368

producers

20,810

slide27

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
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
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
three categories
Three Categories
  • Hydrologic cycle
    • Water
  • Atmospheric cycles
    • Nitrogen and carbon
  • Sedimentary cycles
    • Phosphorus and sulfur
hydrologic cycle
Hydrologic Cycle

Atmosphere

precipitation onto land 111,000

wind-driven water vapor

40,000

evaporation from land plants (evapotranspiration) 71,000

evaporation from ocean

425,000

precipitation into ocean 385,000

surface and groundwater flow 40,000

Oceans

Land

hubbard brook experiment
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 experiment34
Hubbard Brook Experiment

losses from disturbed

watershed plot

time of

deforestation

aquifer depletion
Aquifer Depletion
  • Green signifies high overdrafts
  • Gold, moderate overdrafts
  • Yellow, insignificant withdrawals
  • Shaded areas show groundwater pollution
  • Blue squares: saltwater intrusion
carbon cycle
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 cycle37

volcanic action

photosynthesis

TERRESTRIAL ROCKS

weathering

Carbon Cycle

diffusion

Atmosphere

Bicarbonate, carbonate

Terrestrial

rocks

Land food webs

Marine food

webs

Soil water

Peat, fossil fuels

Marine Sediments

carbon in the oceans
Carbon in the Oceans
  • Most carbon in the ocean is dissolved carbonate and bicarbonate
  • Ocean currents carry dissolved carbon
carbon in atmosphere
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 Effect
  • Greenhouse gases impede the escape of heat from Earth’s surface
carbon dioxide increase
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
other greenhouse gases
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
Greenhouse Gases

carbon dioxide

methane

nitrous oxide

CFCs

global warming
Global Warming
  • Long-term increase in the temperature of Earth’s lower atmosphere
nitrogen cycle
Nitrogen Cycle
  • Nitrogen is used in amino acids and nucleic acids
  • Main reservoir is nitrogen gas in the atmosphere
nitrogen fixation
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
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 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
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 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 cycle53
Phosphorus Cycle

mining

FERTILIZER

excretion

GUANO

agriculture

weathering

uptake by autotrophs

uptake by autotrophs

weathering

MARINE FOOD WEBS

DISSOLVED IN OCEAN WATER

DISSOLVED IN SOILWATER, LAKES, RIVERS

LAND FOOD WEBS

death, decomposition

death, decomposition

leaching, runoff

sedimentation

setting out

uplifting over geologic time

ROCKS

MARINE SEDIMENTS

phosphorus cycle54
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 effects55
Human Effects
  • In tropical countries, clearing lands for agriculture may deplete phosphorus-poor soils
  • In developed countries, phosphorus runoff is causing eutrophication of waterways