YOUR ROLE IN THE ECOSYSTEM

All life on Earth is interconnected.

All life interacts with the nonliving

environment.

What is an ecosystem?You, all other life forms and all of the nonliving factors in your environment make up the ecosystem.

Ecosystems are influenced by both biotic (living) factors and abiotic (nonliving) factors

Two major things move through the ecosystem, ENERGY and MATTER.

Major DIFFERENCE:

Matter CYCLES, Energy FLOWS in one direction.

What does this mean?

Why does it matter?

Cycling of Matter

•Remember CHNOPS?•Unlike energy, these important elements can be recycled within and between ecosystems.

•Biogeochemical cycles- the passing of matter from one organism to another and from one part of the biosphere to another

The Water Cycle

The Carbon Cycle

LAW: Conservation of MatterNo physical or chemical change can create or destroy any atoms.

All we can ever do is rearrange the atoms that already exist.

We can never throw anything “away”

Energy Flow

The Popcorn Race…1. What was the limiting factor affecting how much popcorn

could be carried?

2. When did the popcorn spill?

3. What would happen if there were fewer transfers?

What do you think this has to do with food chains?

• Why are food chains rarely more than 4 or 5 members (trophic levels) long?

Where does the 90% go? What law is this?

Laws of Thermodynamics

First Law: (CHANGE) Energy is neither created nor destroyed but may be converted from one form to another.

Second Law: (LOSS) In any energy conversion, you will end up with less usable energy thanyou started with.

The 10% Rule: 2nd Law of Thermodynamics in action

•As you travel up the food chain, the amount of energy transferred to each organism declines –• only 10% of the energy is passed on to the next consumer• the remaining 90% is either:

1. Energy lost as heat,2.Energy/biomass is used for growth 3. Biomass excreted as waste

•Actually 5-20%

Food Chains•Represents the transfer of matter & energy within an ecosystemShown by arrows

•Include “trophic levels”Producers, consumers, decomposers

Food ChainsA food chain ALWAYS

starts with a producer

The 2nd trophic level is USUALLY a herbivore (can sometimes be an omnivore)

Although not always shown,

all consumers are eventually consumed & recycled by decomposers

How would you label these trophic levels?

A Forest Food Chain

GRASS

MOUSE

SNAKE

HAWK

1st Trophic Level

2nd trophic Level

3rd Trophic

level

4th Trophic

level

A Forest Food Chain

GRASS

MOUSE

SNAKE

HAWK

Producer 1st Consume

r

2nd Consume

r

3rd Consume

r

1st Trophic Level

2nd trophic Level

3rd Trophic

level

4th Trophic

level

A Forest Food Chain

GRASS

MOUSE

SNAKE

HAWK

Producer 1st Consume

r

2nd Consume

r

3rd Consume

rHerbivore Carnivore Carnivore

1st Trophic Level

2nd trophic Level

3rd Trophic

level

4th Trophic

levelWhat’s still missing?

True or False?

If you ate 20 pounds of food,

you would gain 20 pounds

Discussion…

•Why are food chains rarely more than 4 or 5 members long?

•Keep in mind the popcorn race…

GLOBAL FOOD CRISIS…

http://www.youtube.com/watch?v=tSizops50Eo

Pyramid of Energy Flow - Pyramid of BiomassWhy might eating at a lower trophic level be a good idea?

Heat

Heat

Heat

Heat

Heat

1010

100100

1,0001,000

10,00010,000Usable energyUsable energy

Available atAvailable atEach tropic levelEach tropic level(in kilocalories)(in kilocalories)

ProducersProducers(phytoplankton)(phytoplankton)

Primaryconsumers

(zooplankton)

Secondaryconsumers

(perch)

Tertiaryconsumers(human)

Decomposers

Discussion…

•Why could the earth support more people if they eat at lower trophic levels?

So who is in charge?Activity: Tragedy of the Commons

TRAGEDY OF THE COMMONSWhat are the top environmental problems that we face

today?

Resource Depletion

•Natural resource = natural material used by humans• renewable and nonrenewable

•Depletion = large fraction of the resource is used up

Tragedy of the Commons What is it?

•Commons = areas of land that belong to

no one and everyone. •The Tragedy: No one takes responsibility

for shared common resource..

Example: People grazed cows/sheep on land•put as many animals as they could•“If I don’t use this resource someone else will”•No thought of others or the future•No sustainability

So, what’s the problem?

•Short term interests of individuals

vs.•Long term well being of society

Discussion questions

•Did everyone try to take as many as possible?  Why or Why not?  Does society reward those with the “most”?

•Did anyone sacrifice the # of fish, for the good of the community?  Why or why not?  Does society ever reward that type of person?

Analysis Questions

•What other common resources might be represented by the paperclips?

•What happened to all the paperclips in the first year of game one? Why?

•How does this relate to these words: infinite/finite, depletion, sustainability?

Sustainability

•meeting the needs of the present without damaging the environment or depleting a resource for future generations