Transcript Ecosystems and Nutrient Cycles

Ecosystems
Essential Questions:
 What limits the production in ecosystems?
 How do nutrients move in the ecosystem?
 How does energy move through the ecosystem?
Ecosystem
 All the organisms in a community plus abiotic
factors

ecosystems are transformers of energy
& processors of matter
 Ecosystems are self-sustaining

what is needed?
 capture energy
 transfer energy
 cycle nutrients
Ecosystem inputs
constant
energy flows
input
of
through
energy
nutrients cycle
Matter
cannot
Don’t forget
laws of or
bethe
created
Physics!
destroyed
nutrients
can only
cycle
biosphere
inputs
 energy
 nutrients
Food chains
 Trophic levels
feeding relationships
 start with energy from
the sun
 captured by plants



1st
sun
top carnivore
Level 3
Secondary consumer
carnivore
Level 2
Primary consumer
heterotrophs
herbivore
level of all food chains
food chains usually go Level 1
Producer
up only 4 or 5 levels
 inefficiency of energy
transfer

Level 4
Tertiary consumer
all levels connect to
decomposers
autotrophs
Decomposers
Bacteria
Fungi
Energy flows through food chains
sun
Energy is
incorporated
into a
community by
what group?
secondary
consumers
(carnivores)
primary consumers
(herbivores)
producers (plants)
loss of
energy
loss of
energy
Inefficiency of energy transfer
 Loss of energy between levels of food
sun
chain

To where is the energy lost? The cost of living!
17%
growth
only this energy
moves on to the
next level in
the food chain
energy lost to
daily living
33%
cellular
respiration
50%
waste (feces)
sun
Ecological pyramid
 Loss of energy between levels of food chain

can feed fewer animals in each level
Average of 10%
energy
available for
next level
Notice only 1% of
sunlight energy
converted by plants
Humans in food chains
 Energy dynamics of ecosystems have important
implications for human populations
 How much energy is available if we are:
 carnivores? vegetarians?
Seems to be
easier/cheaper to
support a large
population on
grain than on
beef!
Productivity
 Primary productivity: Term for the rate
which producers photosynthesize
organic compounds in an ecosystem.


Gross primary productivity: total amount of photosynthetic
biomass production in an ecosystem
Net Primary Productivity = GPP – respiration cost
 Ecosystems with greater productivity have
more sunlight, water and nutrients.
What you need to be able to do:
 Using the laws of conservation of matter
and energy to do some basic accounting
and determine different aspects of energy
and matter usage in a community.
 Remember: Inputs have to equal outputs
Sample problem #1
 Total energy output?

.75 kcal
 How much is used to
build biomass or
Secondary
Production?

.05 kcal
 What % is not being
efficiently used for
biomass?

93%
Sample problem #2
 A caterpillar consumes 100 kcal of
energy. It uses 35 kcal for cell
respiration, and loses 50 kcal as waste.
Determine the trophic efficiency for its
creation of new biomass.
Total energy consumed = 100 kcal
 Lost and Respired: 35 + 50 = 85 kcal
 Total energy for growth: 15 kcal

 Efficiency (%) = 15/100 = .15 or 15%
Generalized
Nutrient
cycling
consumers
producers
consumers
decomposers
nutrients
nutrients
ENTER FOOD
CHAIN
made
available
= made available
to producers
to producers
Decomposition
connects all
trophic levels
return to
abiotic
reservoir
abiotic
reservoir
geologic
processes
Carbon cycle
CO2 in
atmosphere
Combustion of fuels
Industry and home
Diffusion
Respiration
Photosynthesis
Plants
Animals
Dissolved CO2
Bicarbonates
Photosynthesis
Animals
Plants and algae
Carbonates in sediment
abiotic reservoir:
 CO2 in atmosphere
enter food chain:
 photosynthesis =
carbon fixation in
Calvin cycle
recycle:

return to abiotic:
 respiration
 combustion
Deposition of
dead material
Deposition
of dead
material
Fossil fuels
(oil, gas, coal)
Nitrogen cycle
abiotic reservoir:
 N in atmosphere
enter food chain:
 nitrogen fixation by soil & aquatic bacteria
recycle:
 decomposing & nitrifying bacteria
return to abiotic:
 denitrifying bacteria
Atmospheric
nitrogen
Carnivores
Herbivores
Birds
Plankton with
nitrogen-fixing
bacteria
Plants
Death, excretion, feces
Fish
excretion
Decomposing bacteria
amino acids
Ammonifying bacteria
loss to deep sediments
Nitrogen-fixing
bacteria
(plant roots)
Nitrogen-fixing
bacteria
(soil)
Nitrifying bacteria
soil nitrates
Denitrifying
bacteria
abiotic reservoir:
 rocks, minerals, soil
enter food chain:
 erosion releases
soluble phosphate
 uptake by plants
recycle:
 decomposing
bacteria & fungi
return to abiotic:
 loss to ocean
sediment
Phosphorus cycle
Plants
Land
animals
Animal tissue
Urine and feces
Soluble soil
phosphate
Decomposers
(bacteria and
fungi)
Loss in
drainage
Rocks and
minerals
Decomposers Phosphates
(bacteria & fungi) in solution
Animal tissue
and feces
Aquatic
animals
Plants and
algae
Precipitates
Loss to deep sediment
abiotic reservoir:
 surface & atmospheric water
enter food chain:
 precipitation & plant uptake
recycle:
 transpiration
return to abiotic:
 evaporation & runoff
Water cycle
Solar energy
Transpiration
Water vapor
Evaporation
Precipitation
Oceans
Runoff
Lakes
Percolation in soil
Groundwater
Aquifer
Transpiration
Why does
water flow
into, up
and out of
a plant?
We will discuss
process in
detail soon!
Breaking the water cycle
 Deforestation breaks the water cycle

groundwater is not transpired to the
atmosphere, so precipitation is not
created
forest  desert
desertification
Effects of deforestation
40% increase in runoff
loss of water
loss into
surface water
80 nitrate levels in runoff
Concentration
of nitrate (mg/l )

 60x loss in nitrogen
 10x loss in calcium
40
loss out of
ecosystem!
4
Deforestation
2
Why is
0
nitrogen
1965 so
important?
1966
1967
Year
1968