Ecosystems and the
Biosphere Outline
Ecosystems
• Processes in an ecosystem
Ecosystem
Ecology
– Production, respiration, decomposition
• How energy and nutrients move through an
ecosystem
Biosphere
• Biogeochemical Cycles
• Gaia Hypothesis
Ecosystems overview:
Biotic Components:
Pop dynamics
Trophic dynamics
Ecosystem: all the organisms living in an
area
As well as all the abiotic factors or
physical environment with which they
interact
Ecosystem dynamics includes
energy flow and chemical cycling
• Transformers of energy and processors
of matter
• Energy flow in an ecosystem obeys the
laws of thermodynamics….
Abiotic Components: the nonliving components
the physical and chemical environment of the biota
Sunlight
Water/moisture
Temperature
Soil or water chemistry
Precipitation
Trophic relationships in ecosystems
Energy and nutrients move
through trophic levels
• Primary producers (autotrophs)
• Consumers (herbivores and
predators)
• Decomposers (detritivores)
connects trophic levels -
Predators
recycle essential chemical
elements
Herbivores
Decomposer
Producer
1
Trophic relationships in ecosystems
Energy flows through an ecosystem
1st Law?
Conservation of Energy:
• Energy is neither created nor destroyed
–Entering as light and exiting as heat
Tertiary
consumers
Microorganisms
and other
detritivores
See Fig
55.3,
web
activity
55.2
Secondary
consumers
Primary consumers
Detritus
Primary producers
Heat
Key
Chemical cycling
Energy Flow is Controlled by the
Laws of Thermodynamics
• The primary source of energy that
ecosystems use is sunlight
• The first law implies the only energy available
for growth in the ecosystem is what is
photosynthesized
Sun
Energy flow
Physical and chemical factors limit
primary production in ecosystems
• Gross Primary Production (GPP) - total primary
production in an ecosystem
• Primary production
– the amount of light energy converted to
chemical energy by autotrophs during a given
time period
• Only NPP is available to consumers
Gross and Net Primary Production
125
360
O pen ocean
C o n tin e n ta l s h e lf
E s tu a ry
1 ,5 0 0
A lg a l b e d s a n d re e f s
U p w e llin g z o n e s
– All the energy produced by Photosynthesis
• Some energy is stored in the growing plants, some
is respired
• Net primary production (NPP)
– GPP minus the energy used by the primary producers
(respiration)
– The energy stored in biomass
• So - the extent of photosynthetic
production sets the spending limit for the
energy budget of the entire ecosystem
Different
ecosystems vary
considerably in
their net primary
production
Gross and Net Primary Production
2 ,5 0 0
Overall, terrestrial ecosystems contribute
about two-thirds of global NPP and marine
ecosystems about one-third
North Pole
500
E x tre m e d e s e rt, ro c k , s a n d , ic e
3 .0
90
D e s e rt a n d s e m id e s e rt s c ru b
T ro p ic a l ra in f o re s t
60°N
2 ,2 0 0
Savanna
C u ltiv a te d la n d
B o re a l f o re s t (ta ig a )
30°N
900
600
800
600
700
T e m p e ra te g ra s s la n d
W o o d la n d a n d s h ru b la n d
T u n d ra
Equator
140
T ro p ic a l s e a s o n a l f o re s t
T e m p e ra te d e c id u o u s f o re s t
1 ,6 0 0
1 ,2 0 0
1 ,3 0 0
T e m p e ra te e v e rg re e n f o re s t
S w a m p a n d m a rs h
L a k e a n d s tre a m
30°S
60°S
2 ,0 0 0
250
0
500
1 ,0 0 0 1 ,5 0 0 2 ,0 0 0 2 ,5 0 0
South Pole
180°
120°W
60°W
0°
60°E
120°E
180°
2
Primary Production in Terrestrial
Ecosystems
Primary Production in Terrestrial
Ecosystems
NPP is related to precipitation
• Climatic factors such as temperature and
moisture, affect primary production
• Temperature effects – enzyme activity
• Wet and dry climates have different primary
productivity
Energy Flow is Controlled by the
Laws of Thermodynamics
2nd Law?
Entropy:
• Transfers of energy are not 100% efficient
Secondary production: amount of chemical
energy in a consumers’ food that is
converted to their own new biomass
• Much energy in food is lost as heat
• As energy flows from organism to organism –
the amount of energy available for growth,
maintenance, etc. decreases
Production Efficiency
About 15% of the
energy in the leaf is
used for secondary
production
Trophic Efficiency and
Ecological Pyramids
Trophic efficiency
Plant material
eaten by caterpillar
– Percent of production transferred from one
trophic level to the next
– Usually ranges from 5% to 20%
200 J
67 J
Feces
Energy transfer between trophic
levels is usually less than 20%
efficient
100 J
33 J
Growth (new biomass)
Cellular
respiration
Predators
– Predictions?
Herbivores
The production efficiency of an organism is the
fraction of energy stored in food that is not used for
respiration
Primary Producer
3
Pyramids of Energy
• This loss of energy with
each transfer in a food
chain
– Can be represented by a
pyramid of net production
Pyramids of Biomass
Grassland
Fig
55.8
Forest
One important ecological
consequence of low
trophic efficiencies
• Sharp decrease at higher
trophic levels
Ocean
Grassland
Forest
Ocean
Inversion
Biological and geochemical processes
move nutrients between organic and
inorganic parts of the ecosystem
Biogeochemical
cycles
The total amount of energy that plants
assimilate by photosynthesis is called
a.
b.
c.
d.
Gross primary production
Net primary production
A pyramid of energy
Succession
Biosphere?
Pop Quiz
• One one side: 4-digit code
• One other: Name, and:
The part of Earth where life occurs and
which biotic processes alter or transform
• What are the 2 main factors that govern
which biome is located in a particular
place?
4
Biosphere Ecology
Biogeochemical Cycles
• Biogeochemical (nutrient) cycles:
movement of chemical elements through
organisms and the physical environment
• Physical environment had four compartments:
oceans
fresh waters
atmosphere
land
Biogeochemical Cycles
• Driven by organism interactions, physical
processes, chemical processes
• Strongly interrelated
• Humans have altered all biogeochemical
cycles
The Carbon Cycle
• Most C in organisms comes from CO2 How?
• Photosynthesis removes carbon from the
atmosphere
• Heterotrophs get C from?
• Respiration returns carbon to the
atmosphere
Figure 58.6 The Global Carbon Cycle
The Carbon Cycle
• Most stored in the oceans.
• On land – most C is in the soil (detritus)
• Fossil fuels - C was converted to such as
oil, natural gas, coal, and peat.
• Burning of these fossil fuels (and wood)
releases C to the atmosphere
Greenhouse gases (water vapor, CO2, and O3 etc.) trap heat
that Earth radiates back to space.
Without an atmosphere, the average surface temperature of
Earth would be about –18°C, rather than its actual +17°C.
5
Figure
58.7
Temp normally fluctuates
Humans are forcing climate change
6