Ecosystem Energy Flow-

Productivity

biosphere

ecosystem

community

population

Studying organisms in their environment

organism

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

biosphere

Ecosystem inputs

constant input

of energy

energy flows

through

nutrients cycle

nutrients

can only

cycle

inputs

energy

nutrients

Don’t forgetthe laws of

Physics!

Matter cannotbe created ordestroyed

consumers

decomposers

abiotic

reservoir

nutrients

made available

to producers

geologic

processes

Generalized Nutrient cycling

consumers

consumers

producers

decomposers

abiotic

reservoir

nutrients

ENTER FOOD CHAIN

= made available

to producers

geologic

processes

Decomposition

connects all

trophic levels

return toabiotic

reservoir

Carbon cycleCO2 in

atmosphere

Diffusion RespirationPhotosynthesis

Photosynthesis

Plants and algae

Plants

Animals

Industry and home

Combustion of fuels

Animals

Carbonates in sediment

Bicarbonates

Deposition of

dead material

Deposition

of dead

material

Fossil fuels

(oil, gas, coal)

Dissolved CO2

abiotic reservoir:

CO2 in atmosphere

enter food chain:

photosynthesis =

carbon fixation in

Calvin cycle

recycle:

return to abiotic:

respiration

combustion

Birds

Herbivores

Plants

amino acids

CarnivoresAtmospheric

nitrogen

loss to deep sediments

Fish

Plankton withnitrogen-fixingbacteria

Nitrogen-fixingbacteria

(plant roots)

Nitrogen-fixingbacteria

(soil)

Denitrifyingbacteria

Death, excretion, feces

Nitrifying bacteria

soil nitrates

excretion

Decomposing bacteria

Ammonifying bacteria

Nitrogen cycleabiotic reservoir:

N in atmosphere

enter food chain:

nitrogen fixation by soil & aquatic bacteria

recycle:

decomposing & nitrifying bacteria

return to abiotic:

denitrifying bacteria

Phosphorus cycle

Loss to deep sediment

Rocks andminerals

Soluble soilphosphate

Plants andalgae

Plants Urine

Land animals

Precipitates

Aquaticanimals

Animal tissueand feces

Animal tissueand feces

Decomposers(bacteria and

fungi)

Decomposers(bacteria & fungi)

Phosphatesin solution

Loss indrainage

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

Lakes

Runoff

Percolation in soil

Evaporation

Transpiration

Precipitation

Oceans

Solar energy

AquiferGroundwater

Water cycle

Water vapor

abiotic reservoir:

surface & atmospheric water

enter food chain:

precipitation & plant uptake

recycle:

transpiration

return to abiotic:

evaporation & runoff

Transpiration

We will discuss process in detail soon!

Why does

water flow

into, up

and out of

a plant?

Energy flows through ecosystems

sun

producers (plants)

loss of

energy

loss of

energy

secondary

consumers

(carnivores)

primary consumers

(herbivores)Energy is

incorporated

into a

community by

what group?

Ecosystem dynamics involve two main processes: energy flow

(productivity) and chemical cycling (biogeochemical cycles)

Energy flows through ecosystems

Matter cycles within them

Physical laws govern energy flow and chemical cycling in

ecosystems

Conservation of Energy (first law of thermodynamics)

Energy enters from solar radiation and is lost as heat

Conservation of matter - Chemical elements are continually

recycled within ecosystems

Ecosystems are open systems, absorbing energy and mass and

releasing heat and waste products

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 are

more stable and diverse than ecosystems

with less productivity.

Which ecosystems are most productive?

Energy transfer between trophic levels

is typically only 10% efficient

Net Primary Production (NPP) is the amount

of new biomass added in a given time period

Only NPP is available to consumers

Ecosystems vary greatly in NPP and

contribution to the total NPP on Earth

Limited by light, nutrients and other abiotic factors

Secondary is the amount of chemical energy

in food converted to new biomass

Inefficiency of energy transfer Loss of energy between levels of food chain

To where is the energy lost? The cost of living!

only this energy

moves on to the

next level in

the food chain

17%growth

50%waste (feces)

33%cellularrespiration

energy lost to

daily living

energy lost to

daily living

sun

Production Efficiency

When a caterpillar feeds on a leaf, only about

one-sixth of the leaf’s energy is used for

secondary production

An organism’s production efficiency is the

fraction of energy stored in food that is not

used for respiration

Plant materialeaten by caterpillar

Growth (new biomass;secondary production)

Cellularrespiration

Assimilated

Feces

Not assimilated

100 J

33 J

67 J

200 J

Figure 55.10

Trophic Efficiency and Ecological

Pyramids Trophic efficiency is the percentage of

production transferred from one trophic level

to the next

It is usually about 10% (“10% Law”), with an

actual range of 5% to 20%

Trophic efficiency is multiplied over the length

of a food chain

Ecological pyramid

Loss of energy between levels of food chain

can feed fewer animals in each level

sun

Notice only 1% of

sunlight energy

converted by plants

10% energy

available for

next level

Birds and mammals have efficiencies in the

range of 13%

Fishes have production efficiencies of around

10%

Insects and microorganisms have efficiencies

of 40% or more

WHY??

Interesting Energy production facts:

Dynamics of energy flow in ecosystems have

important implications for the human population

Eating meat is a relatively inefficient in terms of

utilizing photosynthetic production (and water)

Worldwide agriculture could feed many more people

if humans ate only plant material

Fossil fuels used to produce foods

Role of Humans in Energy flow and nutrient

cycling:

Humans in food chains-carbon cycle

Dynamics of energy through ecosystems have important implications for human populations

How much energy does it take to feed a human?

if we are meat eaters?

if we are vegetarian?

Better harvest?

Combustion and water/ ocean

pollution

Humans and 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 deforestationC

on

ce

ntr

ati

on

of

nit

rate

(m

g/l )

1965 1966

Year

2

0

4

40

80

1967 1968

Deforestation

nitrate levels in runoff

40% increase in runoff

loss of water

60x loss in nitrogen

10x loss in calcium

loss into surface water

loss out of ecosystem!

Why isnitrogen soimportant?

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

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 = 100 kcal

Lost and Respired: 35 + 50 = 85 kcal

Total energy for growth: 15 kcal

Efficiency = part/total = 15/100 = .15 (or

15% transfer or 3/20 as fraction)

The “take home” energy defines ecology!