ENERGY FLOW IN ECOSYSTEMENERGY FLOW IN ECOSYSTEM

How does energy flow in an ecosystem?How does energy flow in an ecosystem?

What is a trophic level? What is a trophic level?

ENERGY ENTERS ECOSYTEMENERGY ENTERS ECOSYTEM

All All energyenergy in in ecosystem comes ecosystem comes from the from the sunsun

First law of First law of Thermodynamics: Thermodynamics: EnergyEnergy cannot be cannot be created or created or destroyed (but it destroyed (but it can be transformed can be transformed into stored energy & into stored energy & heat)heat)

ENERGY LEAVES ECOSYSTEMENERGY LEAVES ECOSYSTEM Second law of Second law of

thermodynamics:thermodynamics:Some Some EnergyEnergy is is lostlost when it is when it is

transformedtransformed

In ecosystems, In ecosystems, when when energyenergy is is transformed, some transformed, some energy is lost as energy is lost as HEATHEAT

ENERGY PATHSENERGY PATHS

3 ways to 3 ways to illustrate illustrate energy flowenergy flow

1. Food Chain: Single path

2. Food Web: many paths 3. Food Pyramid

FOOD CHAINSFOOD CHAINS A A food chainfood chain shows the path shows the path

of energy from one organism of energy from one organism to the next. Each level is to the next. Each level is called a called a TROPHIC LEVEL TROPHIC LEVEL ((Troph = feed)

energy flows from producers energy flows from producers to consumersto consumers

arrows mean “arrows mean “is eaten byis eaten by” ” (plant is eaten by herbivore)(plant is eaten by herbivore)

Usually decomposers are left Usually decomposers are left outout

FOOD CHAINS AND WEBSFOOD CHAINS AND WEBS Practice! Draw a food Practice! Draw a food

chain that includes the chain that includes the following organisms:following organisms: grasshoppergrasshopper mousemouse grassgrass owlowl

Now label the organisms Now label the organisms as producers, consumers as producers, consumers (which type?), or (which type?), or decomposersdecomposers PRODUCER

CONSUMER(HERBIVORE)

CONSUMER(CARNIVORE)

CONSUMER(CARNIVORE)

FOOD WEBSFOOD WEBS A A food webfood web shows all feeding relationships in shows all feeding relationships in

an ecosystem (made of many food chains)an ecosystem (made of many food chains)

FOOD WEBSFOOD WEBS Typically, food webs go like this: Typically, food webs go like this:

PRODUCER

CONSUMER(HERBIVORE)

CONSUMER(CARNIVORE)

CONSUMER(OMNIVORE)

DECOMPOSER

remember: remember: decomposersdecomposers receive energy receive energy from all other from all other organisms in organisms in an ecosysteman ecosystem

FOOD CHAINS/WEBS &FOOD CHAINS/WEBS & PYRAMIDS PYRAMIDS (ENERGY; NUMBERS & BIOMASS)(ENERGY; NUMBERS & BIOMASS)

Food chains/webs can be Food chains/webs can be written as a pyramid:written as a pyramid:

Producers form the base Producers form the base of the pyramidof the pyramid

Consumers form the Consumers form the upper layersupper layers

http://www.harcourtschool.com/activity/science_up_close/314/deploy/interface.html

Pyramid of numbers

ENERGY PYRAMIDSENERGY PYRAMIDS

Top Consumer

Energy stored by Secondary Consumers

Energy stored byPrimary Consumers

ENERGY STORED BY PRODUCERS

The energy pyramid The energy pyramid shows energy flow in an shows energy flow in an ecosystem:ecosystem:

How efficient is the transfer of energy among organisms in an ecosystem?

Energy Flow

Lost as Heat

Usable

Energy is Energy is lostlost with each trophic with each trophic ~90% is released to the environment as heat~90% is released to the environment as heat

~10% of the energy is used~10% of the energy is used

Energy is Energy is lostlost with each trophic with each trophic ~90% is released to the environment as heat~90% is released to the environment as heat

~10% of the energy is used~10% of the energy is used

Only Only about about 10% of 10% of the the energy energy from one from one level is level is passed passed on to the on to the next levelnext level

QUICK REVIEWQUICK REVIEW Practice! Practice!

If 100% of the energy is available at the first trophic If 100% of the energy is available at the first trophic level, what percentages of the energy are available at level, what percentages of the energy are available at the second and third trophic levels?the second and third trophic levels?

100%

10%

1%

Copyright Pearson Prentice Hall

3–2

The main source of energy for life on Earth is organic chemical compounds. inorganic chemical compounds. sunlight. producers.

Copyright Pearson Prentice Hall

3–2

How does a food web differ from a food chain? A food web contains a single series of energy

transfers. A food web links many food chains together. A food web has only one trophic level. A food web shows how energy passes from producer

to consumer.

Copyright Pearson Prentice Hall

3–2 The amount of energy represented in each trophic level of consumers in an energy pyramid is about 10% of the level below it. 90% of the level below it. 10% more than the level below it. 90% more than the level below it.

http://www.youtube.com/watch?v=pSwnjhIeX1w