Transcript Trophic level

Chapter 54: Ecosystems
1. What is an ecosystem?
- All the organisms living within an area & all the abiotic factors
they interact with
- Energy flows through while chemicals cycle within an ecosystem
Figure 54.2 An overview of energy and nutrient dynamics in an ecosystem
Tertiary
consumers
Microorganisms
and other
detritivores
Detritus
Secondary
consumers
Primary consumers
Primary producers
Heat
Key
Chemical cycling
Energy flow
Sun
Chapter 54: Ecosystems
1. What is an ecosystem?
- All the organisms living within an area & all the abiotic factors
they interact with
- Energy flows through while chemicals cycle within an ecosystem
2. What is primary productivity?
- Amount of light energy converted to chemical energy by autotrophs
3. What is the difference between Gross PP & Net PP?
- GPP = total primary productivity
- NPP = GPP – respiration (energy used by organisms)
- Storage of chemical energy available to consumers
Figure 54.4 Net primary production of different ecosystems
Open ocean
Continental shelf
Estuary
5.2
0.3
0.1
0.1
4.7
3.5
3.3
2.9
2.7
2.4
1.8
1.7
1.6
1.5
1.3
1.0
0.4
0.4
Algal beds and reefs
Upwelling zones
Extreme desert, rock, sand, ice
Desert and semidesert scrub
Tropical rain forest
Savanna
Cultivated land
Boreal forest (taiga)
Temperate grassland
Woodland and shrubland
Tundra
Tropical seasonal forest
Temperate deciduous forest
Temperate evergreen forest
Swamp and marsh
Lake and stream
0
Key
125
360
65.0
10
5.6
1,500
2,500
1.2
0.9
0.1
0.04
0.9
500
3.0
90
2,200
22
900
600
800
600
700
7.9
9.1
9.6
5.4
3.5
0.6
7.1
4.9
3.8
2.3
0.3
140
1,600
1,200
1,300
2,000
250
20
30
40
50
60
(a) Percentage of Earth’s
surface area
Marine
Terrestrial
Freshwater (on continents)
24.4
0
500 1,000 1,500 2,000 2,500
(b) Average net primary
production (g/m2/yr)
0
5
10
15
20
25
(c) Percentage of Earth’s net
primary production
Figure 54.5 Regional annual net primary production for Earth
North Pole
60N
30N
Equator
30S
60S
South Pole
180
120W
60W
0
60E
120E
180
Chapter 54: Ecosystems
1. What is an ecosystem?
- All the organisms living within an area & all the abiotic factors
they interact with
- Energy flows through while chemicals cycle within an ecosystem
2. What is primary productivity?
- Amount of light energy converted to chemical energy by autotrophs
3. What is the difference between Gross PP & Net PP?
- GPP = total primary productivity
- Amount of light energy converted to chemical energy
by photosynthesis
- NPP = GPP – respiration (energy used by organisms)
- Storage of chemical energy available to consumers
4. What happens to energy at each trophic level?
Figure 54.10 Energy partitioning within a link of the food chain
Plant material
eaten by caterpillar
200 J
67 J
Feces
100 J
33 J
Growth (new biomass)
Cellular
respiration
Chapter 54: Ecosystems
1. What is an ecosystem?
- All the organisms living within an area & all the abiotic factors
they interact with
- Energy flows through while chemicals cycle within an ecosystem
2. What is primary productivity?
- Amount of light energy converted to chemical energy by autotrophs
3. What is the difference between Gross PP & Net PP?
- GPP = total primary productivity
- Amount of light energy converted to chemical energy
by photosynthesis
- NPP = GPP – respiration (energy used by organisms)
- Storage of chemical energy available to consumers
4. What happens to energy at each trophic level?
5. What does the “Pyramid of Net Production” look like?
Figure 54.11 An idealized pyramid of net production
Tertiary
consumers
10 J
Secondary
consumers
100 J
Primary
consumers
Primary
producers
1,000 J
10,000 J
1,000,000 J of sunlight
Rule of 10 = only 10% of energy reaches the next trophic level
- <1% harnessed
by autotrophs
Figure 54.12 Pyramids of biomass (standing crop)
Trophic level
Dry weight
(g/m2)
Tertiary consumers
1.5
Secondary consumers
11
37
809
Primary consumers
Primary producers
(a) Most biomass pyramids show a sharp decrease in biomass at
successively higher trophic levels, as illustrated by data from
a bog at Silver Springs, Florida.
Trophic level
Dry weight
(g/m2)
Primary consumers (zooplankton)
21
Primary producers (phytoplankton)
4
(b) In some aquatic ecosystems, such as the English Channel,
a small standing crop of primary producers (phytoplankton)
supports a larger standing crop of primary consumers (zooplankton).
Figure 54.13 A pyramid of numbers
Trophic level
Tertiary consumers
Number of
individual organisms
3
Secondary consumers
354,904
Primary consumers
708,624
Primary producers
5,842,424
Fig. 54.14 Relative food energy available to the human population
at different trophic levels
Trophic level
Secondary
consumers
Primary
consumers
Primary
producers
- energy is more directly available to vegetarians than carnivores
Chapter 54: Ecosystems
1. What is an ecosystem?
- All the organisms living within an area & all the abiotic factors
they interact with
- Energy flows through while chemicals cycle within an ecosystem
2. What is primary productivity?
- Amount of light energy converted to chemical energy by autotrophs
3. What is the difference between Gross PP & Net PP?
- GPP = total primary productivity
- Amount of light energy converted to chemical energy
by photosynthesis
- NPP = GPP – respiration (energy used by organisms)
- Storage of chemical energy available to consumers
4. What happens to energy at each trophic level?
5. What does the “Pyramid of Net Production” look like?
6. Let’s consider chemical cycling within an ecosystem….
Figure 54.17 Nutrient Cycles
THE CARBON CYCLE
THE WATER CYCLE
CO2 in atmosphere
Transport
over land
Photosynthesis
Solar energy
Cellular
respiration
Net movement of
water vapor by wind
Precipitation
over ocean
Evaporation
from ocean
Precipitation
over land
Burning of
fossil fuels
and wood
Evapotranspiration
from land
Percolation
through
soil
Runoff and
groundwater
Carbon compounds
in water
Higher-level
Primary consumers
consumers
Detritus
Decomposition
THE PHOSPHORUS CYCLE
THE NITROGEN CYCLE
N2 in atmosphere
Rain
Geologic
uplift
Runoff
Assimilation
NO3
Nitrogen-fixing
bacteria in root
nodules of legumes
Plants
Weathering
of rocks
Denitrifying
bacteria
Consumption
Sedimentation
Decomposers
Ammonification
NH3
Nitrogen-fixing
soil bacteria
Nitrifying
bacteria
Nitrification
NO2
NH4+
Nitrifying
bacteria
Soil
Plant uptake
of PO43
Leaching

Decomposition
Chapter 54: Ecosystems
1.
2.
3.
4.
5.
6.
7.
What is an ecosystem?
What is primary productivity?
What is the difference between Gross PP & Net PP?
What happens to energy at each trophic level?
What does the “Pyramid of Net Production” look like?
Let’s consider chemical cycling within an ecosystem….
What happened at the Hubbard Brook Experimental Forest?
- Nutrients stayed within an ecosystem due to plants
Figure 54.19 Nutrient cycling in the Hubbard Brook Experimental
Forest: an example of long-term ecological research
(a) Concrete dams and weirs
built across streams at the
bottom of watersheds
enabled researchers to
monitor the outflow of
water and nutrients from
the ecosystem.
Nitrate concentration in runoff
(mg/L)
(c) The concentration of
nitrate in runoff from the
deforested watershed
was 60 times greater
than in a control
(unlogged) watershed.
(b) One watershed was clear
cut to study the effects of
the loss of vegetation on
drainage and nutrient
cycling.
Deforested
80.0
60.0
40.0
20.0
4.0
3.0
2.0
1.0
0
Completion of
tree cutting
1965
Control
1966
1967
1968
Chapter 54: Ecosystems
1.
2.
3.
4.
5.
6.
7.
What is an ecosystem?
What is primary productivity?
What is the difference between Gross PP & Net PP?
What happens to energy at each trophic level?
What does the “Pyramid of Net Production” look like?
Let’s consider chemical cycling within an ecosystem….
What happened at the Hubbard Brooks Experimental Forest?
- Nutrients stayed within an ecosystem due to plants
8. What is biological magnification?
- Concentration of toxins increase in higher trophic levels
Fig. 54.23 Biological magnification of PCBs in a Great Lakes food web
Concentration of PCBs
Herring
gull eggs
124 ppm
Lake trout
4.83 ppm
Smelt
1.04 ppm
Zooplankton
0.123 ppm
Phytoplankton
0.025 ppm