1. 42
Ecosystems and Energy

2. Do now:
cornlocust  lizard in the above food chain predict what changes would occur if a snake was added as an apex predator
Categorize the following as either primary succession ,secondary succession, neither or both
Of the two, occurs faster.
Happens when soil has never existed
A forest fire is an example
Lichen break down rocks to create soil
Eventually results in a stable climax community
Pioneer communities are present

3. HW questions review:
Science practice skill set: analyzing graphs, making predictions

4. Overview: Cool Ecosystem
An ecosystem consists of all the organisms living in a community, as well as the abiotic factors with which they interact
An example is the unusual community of organisms, including chemoautotrophic bacteria, living below a glacier in Antarctica 4

5. Ecosystems range from a microcosm, such as space under a fallen log or desert spring, to a large area, such as a lake or forest 5

6. Regardless of an ecosystem’s size, its dynamics involve two main processes:
energy flow
chemical cycling 6

7. Concept 42.1: Physical laws govern energy flow and chemical cycling in ecosystems
Ecologists study the transformations of energy and matter within ecosystems
1st law of thermodynamics: energy cannot be created or destroyed.
Where does energy come from?
If trophic levels exhibit 10% rule, where does energy go? 7

8. Conservation of Energy
Laws of physics and chemistry apply to ecosystems, particularly energy flow
Energy enters an ecosystem as solar radiation, is transformed into chemical energy by photosynthetic organisms, and is dissipated as heat 8

9. 2nd law of thermodynamics states that every exchange of energy increases the entropy(disorder) of the universe
Some energy is always lost as heat.
What does this mean in terms of an ecosystems energy requirement? 9

10. Conservation of Mass
The law of conservation of mass states that matter cannot be created or destroyed
Chemical elements are continually recycled within ecosystems
In a forest ecosystem, most nutrients enter as dust or solutes in rain and are carried away in water
Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products 10

11. Energy, Mass, and Trophic Levels
Autotrophs build molecules themselves using photosynthesis or chemosynthesis as an energy source
What is the main difference between the two processes? 11

12. Arrows depict energy flow
Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores)
Arrows depict energy flow 12

13. Decomposition connects all trophic levels
Detritivores, or decomposers, are consumers that derive their energy from detritus, nonliving organic matter
Ex: bacteria and fungi
Decomposition connects all
trophic levels 13

14. Sun Key Chemical cycling Heat Energy flow Primary producers Primary
Figure 42.4
Sun
Key
Chemical cycling
Heat
Energy flow
Primary producers
Primary
consumers
Detritus
Figure 42.4 An overview of energy and nutrient dynamics in an ecosystem
Microorganisms
and other
detritivores
Secondary and
tertiary
consumers 14

15. Concept 42.2: Energy and other limiting factors control primary production in ecosystems
In most ecosystems, primary production is the amount of light energy converted to chemical energy by autotrophs during a given time period
In a few ecosystems, chemoautotrophs are the primary producers 15

16. Ecosystem Energy Budgets
The extent of photosynthetic production sets the spending limit for an ecosystem’s energy budget
How to increase photosynthetic production? 16

17. The Global Energy Budget
The amount of solar radiation reaching Earth’s surface limits the photosynthetic output of ecosystems
Sunlight is absorbed, scattered or reflected by clouds
Sunlight strikes ice/soil
Radiation can only be absorbed by certain wavelength
Only a small fraction of solar energy actually strikes photosynthetic organisms 17

18. Gross and Net Production
Total primary production is known as the ecosystem’s gross primary production (GPP)
GPP is measured as the conversion of chemical energy from photosynthesis per unit time 18

19. Net primary production (NPP) is GPP minus energy used by primary producers for “autotrophic respiration” (Ra)
NPP is expressed as
Energy per unit area per unit time (J/m2  yr), or
Biomass added per unit area per unit time (g/m2  yr)
NPP = GPP − Ra 19

20. NPP is the amount of new biomass added in a given time period
Out of GPP and NPP which is available to consumers?
Ecosystems vary greatly in NPP and contribution to the total NPP on Earth 20

21. Technique 80 Snow Clouds 60 Vegetation Percent reflectance 40 Soil 20
Figure 42.5
Technique 80
Snow
Clouds 60
Vegetation
Percent reflectance 40
Soil 20
Figure 42.5 Research method: determining primary production with satellites
Liquid water
400
600
800
1,000
1,200
Visible
Near-infrared
Wavelength (nm) 21

22. Which biomes might have high NPP?

23. Net primary production (kg carbon/m2 • yr)
Figure 42.6
Net primary production
(kg carbon/m2 • yr) 3 2 1
Figure 42.6 Global net primary production 23

24. Tropical rain forests, estuaries, and coral reefs are among the most productive ecosystems per unit area
Marine ecosystems are relatively unproductive per unit area but contribute much to global net primary production because of their volume
Video: Oscillatoria 24

25. Primary Production in Aquatic Ecosystems
Which factors affect NPP?
In marine and freshwater ecosystems, both light and nutrients control primary production 25

26. Light Limitation
Depth of light penetration affects primary production in the photic zone of an ocean or lake
About half the solar radiation is absorbed in the first 15 m of water, and only 5–10% reaches a depth of 75 m 26

27. (millions of cells per mL) Phytoplankton density
Figure 42.7
Results 30
Ammonium
enriched
Phosphate
enriched 24
Unenriched
control 18
(millions of cells per mL)
Phytoplankton density 12
Figure 42.7 Inquiry: Which nutrient limits phytoplankton production along the coast of Long Island? 6 A B C D E F G
Collection site 27

28. Nutrient Limitation
More than light, nutrients limit primary production in geographic regions of the ocean and in lakes
A limiting nutrient is the element that must be added for production to increase in an area
Nitrogen and phosphorous are the nutrients that most often limit marine production
Nutrient enrichment experiments confirmed that nitrogen was limiting phytoplankton growth off the shore of Long Island, New York 28

29. Table 42.1
Table 42.1 Nutrient enrichment experiment for Sargasso Sea samples 29

30. Experiments in the Sargasso Sea in the subtropical Atlantic Ocean showed that iron limited primary production 30

31. Upwelling of nutrient-rich waters in parts of the oceans contributes to regions of high primary production
The addition of large amounts of nutrients to lakes has a wide range of ecological impacts 31

32. This has led to the use of phosphate-free detergents
In some areas, sewage runoff has caused eutrophication of lakes, which can lead to loss of most fish species
In lakes, phosphorus limits cyanobacterial growth more often than nitrogen
This has led to the use of phosphate-free detergents 32

33. Terrestrial Ecosystems
1,400
1,200
1,000
Net annual primary production
(above ground, dry g/m2 • yr)
800
600
400
Figure 42.8 A global relationship between net primary production and mean annual precipitation for terrestrial ecosystems
200 20 40 60 80
100
120
140
160
180
200
Mean annual precipitation (cm) 33

34. Primary Production in Terrestrial Ecosystems
In terrestrial ecosystems, temperature and moisture affect primary production on a large scale 34

35. Nutrient Limitations and Adaptations That Reduce Them
On a more local scale, a soil nutrient is often the limiting factor in primary production
In terrestrial ecosystems, nitrogen is the most common limiting nutrient
Phosphorus can also be a limiting nutrient, especially in older soils 35

36. Various adaptations help plants access limiting nutrients from soil
Some plants form mutualisms with nitrogen-fixing bacteria
Many plants form mutualisms with mycorrhizal fungi; these fungi supply plants with phosphorus and other limiting elements
Roots have root hairs that increase surface area
Many plants release enzymes that increase the availability of limiting nutrients 36

37. Concept 42.3: Energy transfer between trophic levels is typically only 10% efficient
Secondary production of an ecosystem is the amount of chemical energy in food converted to new biomass during a given period of time 37

38. Production Efficiency
When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary production
Net secondary production is the energy stored in biomass
An organism’s production efficiency is the fraction of energy stored in food that is not used for respiration
Production
efficiency =
Net secondary production × 100%
Assimilation of primary production 38

39. secondary production)
Figure 42.9
Plant material
eaten by caterpillar
200 J
67 J
Cellular
respiration
Figure 42.9 Energy partitioning within a link of the food chain
100 J
Feces
33 J
Not assimilated
Growth (new biomass;
secondary production)
Assimilated 39

40. Birds and mammals have efficiencies in the range of 13%
Insects and microorganisms have efficiencies of 40% or more
Why is there such a large discrepancy between the two?
Endothermy (insects and mammals) requires higher levels of energy 40

41. Trophic Efficiency and Ecological Pyramids
Trophic efficiency is the percentage of production transferred from one trophic level to the next, usually about 10%
Trophic efficiencies take into account energy lost through respiration and contained in feces, as well as the energy stored in unconsumed portions of the food source
Trophic efficiency is multiplied over the length of a food chain 41

42. Approximately 0.1% of chemical energy fixed by photosynthesis reaches a tertiary consumer
A pyramid of net production represents the loss of energy with each transfer in a food chain 42

43. Tertiary consumers 10 J Secondary consumers 100 J Primary consumers
Figure 42.10
Tertiary
consumers
10 J
Secondary
consumers
100 J
Primary
consumers
1,000 J
Primary
producers
Figure An idealized pyramid of net production
10,000 J
1,000,000 J of sunlight 43

44. In a biomass pyramid, each tier represents the standing crop (total dry mass of all organisms) in one trophic level
Most biomass pyramids show a sharp decrease at successively higher trophic levels 44

45. Dry mass (g/m2) 1.5 11 37 809 Dry mass (g/m2) 21 4
Figure 42.11
Trophic level
Dry mass
(g/m2)
Tertiary consumers
1.5
Secondary consumers 11
Primary consumers 37
Primary producers
809
(a) Most ecosystems (data from a Florida bog)
Trophic level
Dry mass
(g/m2)
Figure Pyramids of biomass (standing crop)
Primary consumers (zooplankton) 21
Primary producers (phytoplankton) 4
(b) Some aquatic ecosystems (data from the English Channel) 45

46. Turnover time is the ratio of the standing crop biomass to production
Certain aquatic ecosystems have inverted biomass pyramids: producers (phytoplankton) are consumed so quickly that they are outweighed by primary consumers
Turnover time is the ratio of the standing crop biomass to production
Turnover time =
Standing crop (g/m2)
Production (g/m2  day) 46

47. Dynamics of energy flow in ecosystems have important implications for the human population
Eating meat is a relatively inefficient way of tapping photosynthetic production
Worldwide agriculture could feed many more people if humans ate only plant material 47

48. Classwork/exit Slip

49. Concept 42.4: Biological and geochemical processes cycle nutrients and water in ecosystems
Life depends on recycling chemical elements
Decomposers (detritivores) play a key role in the general pattern of chemical cycling 49

50. Decomposition and Nutrient Cycling Rates
Rates at which nutrients cycle in different ecosystems vary greatly, mostly as a result of differing rates of decomposition
The rate of decomposition is controlled by temperature, moisture, and nutrient availability 50

51. Mean annual temperature (°C) R
Figure 42.12
Experiment
Ecosystem type
Results
Arctic 80
Subarctic 70
Boreal
Temperate 60 R U A K O
Grassland 50 Q T
Percent of mass lost G J P
Mountain 40 S D N F 30 C I M L M 20 A H
B,C D B E P 10 G T
H,I S
E,F N L O U
−15
−10 −5 5 10 15 J
Figure Inquiry: How does temperature affect litter decomposition in an ecosystem? K Q
Mean annual temperature (°C) R 51

52. Experiment Ecosystem type Arctic Subarctic Boreal Temperate A
Figure 42.12a
Experiment
Ecosystem type
Arctic
Subarctic
Boreal
Temperate A
Grassland G
Mountain M
B,C D P T
H,I
E,F
Figure 42.12a Inquiry: How does temperature affect litter decomposition in an ecosystem? (part 1: experiment) S N L O U J K Q R 52

53. Mean annual temperature (°C)
Figure 42.12b
Results 80 70 U 60 R O K Q 50 T
Percent of mass lost J P 40 S D N F 30 C I M L 20 A H B E G 10
Figure 42.12b Inquiry: How does temperature affect litter decomposition in an ecosystem? (part 2: results)
−15
−10 −5 5 10 15
Mean annual temperature (°C) 53

54. Decomposition is slow in anaerobic muds
Rapid decomposition results in relatively low levels of nutrients in the soil
For example, in a tropical rain forest, material decomposes rapidly, and most nutrients are tied up in trees and other living organisms
Cold and wet ecosystems store large amounts of undecomposed organic matter, as decomposition rates are low
Decomposition is slow in anaerobic muds 54

55. Do now:
What are the most important factors which limit primary production in terrestrial ecosystems? Aquatic?
Explain why this biomass pyramid might be inverted
Hypothetical scenario: all the plants in an ecosystem absorb 1,000 J of sunlight energy. They create 90 J of energy found in glucose. 15 J is lost in respiration and 15 J is lost in heat.
Identify: GPP,NPP, secondary production.

56. Biogeochemical Cycles
Nutrient cycles in ecosystems involve biotic and abiotic components and are often called biogeochemical cycles
Water cycle
Carbon cycle*
Nitrogen cycle*
Phosphorous cycle
**most often tested 56

57. The water cycle Movement over land by wind Precipitation over land
Figure 42.13a
Movement over
land by wind
Precipitation
over land
Precipitation
over ocean
Evaporation
from ocean
Evapotranspiration
from land
Figure 42.13a Exploring water and nutrient cycling (part 1: water)
Percolation
through
soil
Runoff and
groundwater
The water cycle 57

58. Water is essential to all organisms
The Water Cycle
Water is essential to all organisms
Liquid water is the primary physical phase in which water is used
The oceans contain 97% of the biosphere’s water; 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater
Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater
Animation: Carbon Cycle 58

59. The carbon cycle CO2 in atmosphere Photosynthesis Photo- synthesis
Figure 42.13b
CO2 in
atmosphere
Photosynthesis
Photo-
synthesis
Cellular
respiration
Burning of
fossil fuels
and wood
Phyto-
plankton
Consumers
Figure 42.13b Exploring water and nutrient cycling (part 2: carbon)
Consumers
Decomposition
The carbon cycle 59

60. The nitrogen cycle N2 in atmosphere Reactive N gases Industrial
Figure 42.13c
N2 in
atmosphere
Reactive N
gases
Industrial
fixation
Denitrification
N fertilizers
Fixation
Runoff
Dissolved
organic N
NO3−
Terrestrial
cycling N2
NO3−
NH4
Aquatic
cycling
Denitri-
fication
Figure 42.13c Exploring water and nutrient cycling (part 3: nitrogen)
Decomposition
and
sedimentation
Decom-
position
Assimilation
NO3−
Fixation
in root
nodules
Uptake of
amino acids
Ammoni-
fication
Nitrification
NH4
The nitrogen cycle 60

61. The nitrogen cycle Terrestrial N2 cycling Denitri- fication
Figure 42.13cb
Terrestrial
cycling N2
Denitri-
fication
Assimilation
Decom-
position
NO3−
Fixation
in root
nodules
Uptake of
amino acids
Figure 42.13cb Exploring water and nutrient cycling (part 3b: terrestrial nitrogen cycle)
Ammoni-
fication
Nitrification
NH4
The nitrogen cycle 61

62. Do now:
What are main reservoirs that act as a source for carbon dioxide?
What is the effect of human activity on the amount of carbon sinks?
What is nitrogen fixation?

63. Go over HW:
Global warming packet
Stevef palumbi lesson

64. Carbon-based organic molecules are essential to all organisms
The Carbon Cycle
Carbon-based organic molecules are essential to all organisms
Photosynthetic organisms convert CO2 to organic molecules that are used by heterotrophs
Carbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, the atmosphere, and sedimentary rocks 64

65. CO2 is taken up by the process of photosynthesis and released into the atmosphere through cellular respiration
Volcanic activity and the burning of fossil fuels also contribute CO2 to the atmosphere 65

66. Nitrogen is a component of amino acids, proteins, and nucleic acids
The Nitrogen Cycle
Nitrogen is a component of amino acids, proteins, and nucleic acids
The main reservoir of nitrogen is the atmosphere (N2), though this nitrogen must be converted to NH4+ or NO3− for uptake by plants, via nitrogen fixation by bacteria 66

67. Denitrification converts NO3− back to N2
Organic nitrogen is decomposed to NH4+ by ammonification, and NH4+ is decomposed to NO3− by nitrification
Denitrification converts NO3− back to N2 67

68. The phosphorus cycle Wind-blown dust Geologic uplift Weathering
Figure 42.13d
Wind-blown
dust
Geologic
uplift
Weathering
of rocks
Runoff
Consumption
Decomposition
Plant
uptake
of PO43−
Plankton
Dissolved
PO43−
Uptake
Leaching
Figure 42.13d Exploring water and nutrient cycling (part 4: phosphorus)
Sedimentation
Decomposition
The phosphorus cycle 68

69. Phosphate (PO43−) is the most important inorganic form of phosphorus
The Phosphorus Cycle
Phosphorus is a major constituent of nucleic acids, phospholipids, and ATP
Phosphate (PO43−) is the most important inorganic form of phosphorus
The largest reservoirs are sedimentary rocks of marine origin, the soil, oceans, and organisms
Phosphate binds with soil particles, and movement is often localized 69

70. Case Study: Nutrient Cycling in the Hubbard Brook Experimental Forest
The Hubbard Brook Experimental Forest has been used to study nutrient cycling in a forest ecosystem since 1963
The research team constructed a dam on the site to monitor loss of water and minerals
They found that 60% of the precipitation exits through streams and 40% is lost by evapotranspiration
Most mineral nutrients were conserved in the system 70

71. Nitrate concentration
Figure 42.14
(a)
Concrete dam
and weir
(b) Clear-cut watershed 80
Deforested 60 40
Figure Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research 20
Nitrate concentration
in runoff (mg/L)
Completion of
tree cutting 4 3
Control 2 1
1965
1966
1967
1968
(c) Nitrate in runoff from watersheds 71

72. (a) Concrete dam and weir
Figure 42.14a
Figure 42.14a Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research (part 1: dam and weir)
(a) Concrete dam and weir 72

73. (b) Clear-cut watershed
Figure 42.14b
Figure 42.14b Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research (part 2: clear-cut watershed)
(b) Clear-cut watershed 73

74. Nitrate concentration
Figure 42.14c 80
Deforested 60 40 20
Nitrate concentration
in runoff (mg/L)
Completion of
tree cutting 4 3
Control 2 1
Figure 42.14c Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research (part 3: nitrate runoff)
1965
1966
1967
1968
(c) Nitrate in runoff from watersheds 74

75. In one experiment, the trees in one valley were cut down, and the valley was sprayed with herbicides75

76. Net losses of water were 3040% greater in the deforested site than in the undisturbed (control) site
Nutrient loss was also much greater in the deforested site compared with the undisturbed site
For example, nitrate levels increased 60 times in the outflow of the deforested site
These results showed that the amount of nutrients leaving a forest ecosystem is controlled mainly by plants 76

77. Concept 42.5: Restoration ecologists help return degraded ecosystems to a more natural state
Given enough time, biological communities can recover from many types of disturbances
Restoration ecology seeks to initiate or speed up the recovery of degraded ecosystems
Two key strategies are bioremediation and augmentation of ecosystem processes 77

78. (a) In 1991, before restoration In 2000, near the completion of
Figure 42.15
Figure A gravel and clay mine site in New Jersey before and after restoration
(a) In 1991, before restoration
In 2000, near the completion of
restoration
(b) 78

79. (a) In 1991, before restoration
Figure 42.15a
Figure 42.15a A gravel and clay mine site in New Jersey before and after restoration (part 1: before)
(a) In 1991, before restoration 79

80. (b) In 2000, near the completion of restoration
Figure 42.15b
Figure 42.15b A gravel and clay mine site in New Jersey before and after restoration (part 2: after)
(b) In 2000, near the completion of restoration 80

81. Bioremediation
Bioremediation is the use of organisms to detoxify ecosystems
The organisms most often used are prokaryotes, fungi, or plants
These organisms can take up, and sometimes metabolize, toxic molecules
For example, the bacterium Shewanella oneidensis can metabolize uranium and other elements to insoluble forms that are less likely to leach into streams and groundwater 81

82. soluble uranium (M) Concentration of
Figure 42.16 6 5 4
soluble uranium (M)
Concentration of 3 2 1 50
100
150
200
250
300
350
400
Figure Bioremediation of groundwater contaminated with uranium at Oak Ridge National Laboratory, Tennessee
Days after adding ethanol
(a)
Wastes containing uranium, Oak Ridge
National Laboratory
(b)
Decrease in concentration of soluble uranium
in groundwater 82

83. Wastes containing uranium, Oak Ridge National Laboratory (a)
Figure 42.16a
Figure 42.16a Bioremediation of groundwater contaminated with uranium at Oak Ridge National Laboratory, Tennessee (part 1: photo)
Wastes containing uranium, Oak Ridge
National Laboratory
(a) 83

84. soluble uranium (M) Concentration of
Figure 42.16b 6 5 4
soluble uranium (M)
Concentration of 3 2 1
Figure 42.16b Bioremediation of groundwater contaminated with uranium at Oak Ridge National Laboratory, Tennessee (part 2: graph) 50
100
150
200
250
300
350
400
Days after adding ethanol
Decrease in concentration of soluble uranium
in groundwater
(b) 84

85. Biological Augmentation
Biological augmentation uses organisms to add essential materials to a degraded ecosystem
For example, nitrogen-fixing plants can increase the available nitrogen in soil
For example, adding mycorrhizal fungi can help plants to access nutrients from soil 85

86. Restoration Projects Worldwide
The newness and complexity of restoration ecology require that ecologists consider alternative solutions and adjust approaches based on experience 86

87. Kissimmee River, Florida Succulent Karoo, South Africa
Figure 42.17
Kissimmee River, Florida
Succulent Karoo, South Africa
Figure Exploring restoration ecology worldwide
Maungatautari, New Zealand
Coastal Japan 87

88. Kissimmee River, Florida
Conversion of the Kissimmee River to a 90-km canal threatened many fish and wetland bird populations
Filling 12 km of the canal has restored natural flow patterns to 24 km of the river, helping to foster a healthy wetland ecosystem 88

89. Kissimmee River, Florida
Figure 42.17a
Figure 42.17a Exploring restoration ecology worldwide (part 1: Kissimmee River)
Kissimmee River, Florida 89

90. Succulent Karoo, South Africa
Overgrazing by livestock has damaged vast areas of land in this region
Restoration efforts have included revegetating the land and employing sustainable resource management 90

91. Succulent Karoo, South Africa
Figure 42.17b
Figure 42.17b Exploring restoration ecology worldwide (part 2: Succulent Karoo)
Succulent Karoo, South Africa 91

92. Maungatautari, New Zealand
Introduction of exotic mammals including weasels, rats, and pigs has threatened many native plant and animal species
Restoration efforts include building fences around reserves to exclude introduced species 92

93. Maungatautari, New Zealand
Figure 42.17c
Figure 42.17c Exploring restoration ecology worldwide (part 3: Maungatautari)
Maungatautari, New Zealand 93

94. Coastal Japan
Destruction of coastal seaweed and seagrass beds through development has threatened a variety of fishes and shellfish
Restoration efforts include constructing suitable habitat, transplantation, and hand seeding 94

95. Figure 42.17d
Figure 42.17d Exploring restoration ecology worldwide (part 4: Coastal Japan)
Coastal Japan 95

96. Figure 42.UN01
Figure 42.UN01 Skills exercise: interpreting quantitative data in a table 96

97. Sun Key Chemical cycling Energy flow Heat Primary producers Primary
Figure 42.UN02
Sun
Key
Chemical cycling
Energy flow
Heat
Primary producers
Primary
consumers
Detritus
Figure 42.UN02 Summary of key concepts: energy flow and chemical cycling
Microorganisms
and other
detritivores
Secondary and
tertiary consumers 97

98. Tertiary consumers 10 J Secondary consumers 100 J Primary consumers
Figure 42.UN03
Tertiary
consumers
10 J
Secondary
consumers
100 J
Primary
consumers
1,000 J
Primary
producers
Figure 42.UN03 Summary of key concepts: trophic efficiency
10,000 J
1,000,000 J of sunlight 98