EcosystemsEcosystems• Trophic LevelsTrophic Levels

– Food Chains & WebsFood Chains & Webs

• Energy FlowEnergy Flow• Ecological PyramidsEcological Pyramids

– Number pyramidsNumber pyramids– Biomass pyramidsBiomass pyramids– Energy pyramidsEnergy pyramids

• Biological Biological MagnificationMagnification

Food chains are usually made up Food chains are usually made up of four to five of four to five trophic levelstrophic levels. All . All food chains begin with food chains begin with ProducersProducers ((autotrophsautotrophs), organisms which ), organisms which have the ability to make their own have the ability to make their own “food” or organic compounds.“food” or organic compounds.– Photo-autotrophs Photo-autotrophs use ________ to use ________ to

make their own organic compounds.make their own organic compounds.

Ex)Ex)– Chemo-autotrophs Chemo-autotrophs use use

____________________ to make their ____________________ to make their own food or organic compounds.own food or organic compounds.

Ex)Ex)

Energy Flow in Ecosystems Energy Flow in Ecosystems Occurs in Food ChainsOccurs in Food Chains

sunlightsunlight

inorganic compoundsinorganic compounds

Plants, photosynthetic algae, etcPlants, photosynthetic algae, etc

Sulfur bacteria Sulfur bacteria in deep sea ventsin deep sea vents

Consumers lack the ability to make Consumers lack the ability to make their own organic compoundstheir own organic compounds

ConsumersConsumers ( (heterotrophsheterotrophs) must ) must obtain all their nutrients by eating or obtain all their nutrients by eating or consuming other organisms.consuming other organisms.– Primary consumersPrimary consumers eat eat

producers. These organisms producers. These organisms can also be described as can also be described as ____________, or plant-eaters. ____________, or plant-eaters.

– Secondary consumersSecondary consumers eat eat primary consumers (and primary consumers (and sometimes producers as well). sometimes producers as well). Thus they can also be described Thus they can also be described as ____________ or as ____________ or ___________, accordingly.___________, accordingly.

herbivoresherbivores

carnivorescarnivoresomnivoresomnivores

So what happens to all the dead So what happens to all the dead producers and consumers?producers and consumers?

• _____________ obtain their _____________ obtain their energy by breaking down (dead) energy by breaking down (dead) organic matter into inorganic organic matter into inorganic substances & compounds.substances & compounds.

Ex)Ex)

• The actions of decomposers allow The actions of decomposers allow the return of these more basic the return of these more basic inorganic compounds to the soil or inorganic compounds to the soil or water. water. What happens to these What happens to these compounds in the soil next?compounds in the soil next? (Think about this.)(Think about this.)

DecomposersDecomposers

fungi, bacteria, some fungi, bacteria, some insects / animalsinsects / animals

A A food webfood web is is made up of a made up of a

number of number of interconnected interconnected food chainsfood chains..

At what trophic At what trophic level is the cricket level is the cricket which eats the which eats the plants?plants?

At what level is the At what level is the mouse which eats mouse which eats the plants the plants andand the the cricket?cricket?

Interactions Among Trophic Interactions Among Trophic Levels in a Food WebLevels in a Food Web

• Both Both negativenegative & & positivepositive interactions occur in a interactions occur in a food web:food web:– Predators have a Predators have a ____________________________________ on their prey on their prey– Upper-level carnivores can have an Upper-level carnivores can have an ________________ positive positive

effect on producers and vice versa (how?)effect on producers and vice versa (how?)

• Food web dynamics are Food web dynamics are extremely complexextremely complex due due to these to these directdirect & & indirectindirect interactions! interactions!

Energy Flow Through Energy Flow Through Ecosystems is One-WayEcosystems is One-Way

• Energy enters most ecosystems as Energy enters most ecosystems as _______._______.

• A tiny percent of this light energy is A tiny percent of this light energy is captured for use by producers captured for use by producers during photosynthesisduring photosynthesis– During During photosynthesisphotosynthesis, light energy , light energy

is converted to chemical energy is converted to chemical energy (in (in the form of glucose sugar and other the form of glucose sugar and other chemical compounds).chemical compounds).

Light Light + H+ H22O + COO + CO22 CC66HH1212OO66 + O+ O22

sunlightsunlight

Energy Flow Through Ecosystems is One-Way

• When these organic compounds are broken When these organic compounds are broken apart during apart during cellular respirationcellular respiration, energy is , energy is made available (in the form of ______) to do made available (in the form of ______) to do cellular work: muscle contraction, repair of cellular work: muscle contraction, repair of tissues, reproducing, etc.tissues, reproducing, etc.

CC66HH1212OO66 + O+ O22 ATP ATP + H+ H22O + COO + CO22

• As work is accomplished, energy escapes the As work is accomplished, energy escapes the body in the form of HEAT, which is released body in the form of HEAT, which is released into the environment and dissipates into spaceinto the environment and dissipates into space

• Once energy has been used by an organism Once energy has been used by an organism and lost as HEAT, it is no longer available and lost as HEAT, it is no longer available for re-usefor re-use

• Ecosystems rely on a continuous input of Ecosystems rely on a continuous input of energy from the _____, or some other source energy from the _____, or some other source (chemical).(chemical).

ATPATP

SUNSUN

Ecological Ecological PyramidsPyramids

37 g/m37 g/m2 2 minnow minnow11 g/m11 g/m2 2 snapper snapper

Ecological PyramidsEcological Pyramids are a way to display are a way to display different characteristics of a food chain of different characteristics of a food chain of

a given ecosystema given ecosystem

• Pyramids of Pyramids of numbersnumbers show the relative show the relative number of organisms in number of organisms in each trophic leveleach trophic level

• Pyramids of Pyramids of biomassbiomass show the relative show the relative amount of living organic amount of living organic material in each trophic material in each trophic level (dry weight)level (dry weight)

1 tuna1 tuna

74 seaweed74 seaweed12 minnow12 minnow

5 snapper5 snapper

1.5 g/m1.5 g/m22 tuna tuna

809 g/m2 seaweed

Pyramids of Numbers and Biomass Pyramids of Numbers and Biomass

• Pyramids of numbers Pyramids of numbers or biomass are often or biomass are often widest at the base widest at the base and get smaller as and get smaller as you go up the food you go up the food chain…chain…

• BUT, this is not BUT, this is not always the case… always the case… (Why?)(Why?)

Pyramids of NumbersPyramids of Numbers

1 hawk1 hawk

GrasslandGrassland Temperate ForestTemperate Forest

3 small birds3 small birds

15 crickets15 crickets

50 producers50 producers 2 producers2 producers

How can a pyramid of numbers have a smaller number How can a pyramid of numbers have a smaller number of producers than it does primary consumers?of producers than it does primary consumers?

________________________________

Pyramids of Biomass

• Here is the base of a biomass pyramid that is smaller than the level above it… How is this possible?

• In this case, the smaller mass of phytoplankton (algae, etc.) ________________________________

– This allows a small amount of producers to sustain a larger mass of primary consumers.

reproduces as quickly as it is eaten

• 10% “Rule”10% “Rule”: : On averageOn average, only 10% of the , only 10% of the energyenergy is is conservedconserved as biomass in the transfer from one level to as biomass in the transfer from one level to another.another.

• The remaining 90% is used during metabolism and is “The remaining 90% is used during metabolism and is “lost”lost” in the form of ______, __________, _____________, etc.in the form of ______, __________, _____________, etc.

Pyramids of EnergyPyramids of Energy• Pyramids of energy show Pyramids of energy show

the relative amount of the relative amount of energy stored energy stored in the in the tissues (biomass) of all tissues (biomass) of all the organisms in each the organisms in each trophic level.trophic level.

• Pyramids of energy Pyramids of energy alwaysalways are widest at the are widest at the base and get narrower base and get narrower toward the top. WHY?toward the top. WHY?

HEATHEAT movementmovement waste materialwaste material

Energy Pyramids show us how to Energy Pyramids show us how to minimize our impact on the Earthminimize our impact on the Earth

Food energy available to the human population at Food energy available to the human population at different trophic levels:different trophic levels:

730,000 730,000 Cal/yrCal/yr

(2,000 Cal/day) x (365 days/yr) = 730,000 Cal/yr to support one person(2,000 Cal/day) x (365 days/yr) = 730,000 Cal/yr to support one person

What is the difference in getting those calories from corn directly v. beef?What is the difference in getting those calories from corn directly v. beef?

(7,300,000 Cal of corn to feed cows) - (730,000 Cal to feed people) =(7,300,000 Cal of corn to feed cows) - (730,000 Cal to feed people) =

6,570,000 extra Calories of corn6,570,000 extra Calories of corn

730,000 730,000 Cal/yrCal/yr

7,300,000 7,300,000 Cal/yrCal/yr

Pollution & Pollution & Food ChainsFood Chains

Early days of the DDT era.

1945, New York, Jones Beach State Park:

DDT spraying for mosquito control.

Pollution and Food ChainsChemical pesticides (like DDT) have helped us fight disease and increase agricultural productivity, but not without an ecological cost.

Rachel Carson: environmentalist

• American marine biologist & nature writer

• worked for US Bureau of Fisheries

• 1950’s interested in environmental problems caused by pesticides

• 1962 authored Silent Spring, documenting impact of pesticides like DDT on environment

http://en.wikipedia.org/wiki/Rachel_Carson

http://www.johnehrenfeld.com/2010/01/rachel-carson-and-green-chemis.html

• Silent Spring brought these concerns to the general public and is credited with helping launch modern environmental movement

Biological Magnification Biological Magnification of Non-biodegradable Toxinsof Non-biodegradable Toxins

• DDT is ______________________DDT is ______________________– Once eaten by living things it Once eaten by living things it

cannot be broken downcannot be broken down for for removal from the bodyremoval from the body

– Instead, it is Instead, it is storedstored in the body -- in the body -- mostly in fat tissuemostly in fat tissue

• DDT ______________ as you DDT ______________ as you proceed up the food chainproceed up the food chain– Although Although producersproducers may only have may only have

small concentrations in their cells, small concentrations in their cells, much higher concentrations are much higher concentrations are found in top consumers due to found in top consumers due to magnifying effects of food chain. magnifying effects of food chain. (Can you explain how this happens?)(Can you explain how this happens?)

– This can occur with non-This can occur with non-biodegradable toxins such as biodegradable toxins such as mercurymercury & other heavy metals & other heavy metals

non-biodegradablenon-biodegradable

accumulatesaccumulates

The concentration of DDT found in the lower levels of the food chain may not be significantly harmful…but the higher concentrations found at the top of the chain can be very dangerous

Effects of DDTEffects of DDT

Dead peregrine falcon embryo (development Dead peregrine falcon embryo (development almost completed) found in a nest in SW almost completed) found in a nest in SW Scotland, May 1971. Further analysis Scotland, May 1971. Further analysis revealed this egg contained one of the highest revealed this egg contained one of the highest concentrations of DDT ever recorded in a bird concentrations of DDT ever recorded in a bird in Great Britain.in Great Britain.

DDTDDT causes a bird’s liver to causes a bird’s liver to break down the hormones that break down the hormones that make calcium available during make calcium available during egg production in females. egg production in females.

The result is thin-shelled, The result is thin-shelled, fragile eggs.fragile eggs. Birds at the Birds at the top of food chains, such as the top of food chains, such as the peregrine falcon, the osprey, peregrine falcon, the osprey, and the bald eagle were/are the and the bald eagle were/are the principal victims. principal victims.

With the banning of DDT in With the banning of DDT in many countries (in 1972 in the many countries (in 1972 in the US), dramatic recoveries have US), dramatic recoveries have been observed in populations been observed in populations of all three species.of all three species.

Fact: The time for 95 % Fact: The time for 95 % breakdown for DDT in the breakdown for DDT in the environment is 10 years. environment is 10 years.