Chapter 3Chapter 3Ecosystems and EnergyEcosystems and Energy

The diamondback tarrapinThe diamondback tarrapin

Overview of Chapter 3Overview of Chapter 3

o EcologyEcologyo EnergyEnergy

• First Law of ThermodynamicsFirst Law of Thermodynamics• Second Law of ThermodynamicsSecond Law of Thermodynamics

o Photosynthesis and Cellular RespirationPhotosynthesis and Cellular Respirationo Flow of Energy Through EcosystemsFlow of Energy Through Ecosystems

• Producers, Consumers & DecomposersProducers, Consumers & Decomposers• Ecological PyramidEcological Pyramid• Ecosystem ProductivityEcosystem Productivity

EcologyEcology

o EcologyEcology• ““eco” house & “logy” study ofeco” house & “logy” study of• The study of interactions among and between The study of interactions among and between

organisms in their abiotic environmentorganisms in their abiotic environment• Broadest field in biologyBroadest field in biology

o Biotic- living environmentBiotic- living environment• Includes all organismsIncludes all organisms

o Abiotic- non living or physical environmentAbiotic- non living or physical environment• Includes living space, sunlight, soil, Includes living space, sunlight, soil,

precipitation, etc.precipitation, etc.

EcologyEcology

o Biology is Biology is very very organizedorganized

o Ecologists Ecologists are are interested interested in the in the levels of levels of life above life above that of that of organismorganism

Ecology DefinitionsEcology Definitionso SpeciesSpecies

• A group of similar organisms whose members freely A group of similar organisms whose members freely interbreedinterbreed

o PopulationPopulation• A group of organisms of the same species that A group of organisms of the same species that

occupy that live in the same area at the same timeoccupy that live in the same area at the same time

o CommunityCommunity• All the populations of different species that live and All the populations of different species that live and

interact in the same area at the same timeinteract in the same area at the same time

o EcosystemEcosystem• A community and its physical (abiotic) environmentA community and its physical (abiotic) environment

o LandscapeLandscape• Several interacting ecosystemsSeveral interacting ecosystems

EcologyEcology

o Biosphere contains earth’s communities, Biosphere contains earth’s communities, ecosystems and landscapes, and includes:ecosystems and landscapes, and includes:

• Atmosphere- Atmosphere- gaseous envelope gaseous envelope surrounding earthsurrounding earth

• Hydrosphere- Hydrosphere- earth’s supply of earth’s supply of waterwater

• Lithosphere- soil Lithosphere- soil and rock of the and rock of the earth’s crustearth’s crust

EnergyEnergy

o The ability or The ability or capacity to do workcapacity to do work• Chemical, radiant, Chemical, radiant,

thermal, thermal, mechanical, nuclear, mechanical, nuclear, electricalelectrical

o Energy exists as:Energy exists as:• Stored energy Stored energy

(potential energy) (potential energy) • Kinetic energy Kinetic energy

(energy of motion)(energy of motion)

ThermodynamicsThermodynamics

o Study of energy and its transformationsStudy of energy and its transformationso System- the object being studiedSystem- the object being studied

• Closed System- Does Closed System- Does not exchange energy not exchange energy with surroundings with surroundings (rare in nature)(rare in nature)

• Open System- Open System- exchanges energy exchanges energy with surroundingswith surroundings

Laws of ThermodynamicsLaws of Thermodynamics

o First Law of ThermodynamicsFirst Law of Thermodynamics• Energy cannot be created or destroyed; it Energy cannot be created or destroyed; it

can change from one form to anothercan change from one form to another• Ex: organisms cannot create energy they need to Ex: organisms cannot create energy they need to

survive- they must capture it from another sourcesurvive- they must capture it from another source• Focus is on quantityFocus is on quantity

o Second Law of ThermodynamicsSecond Law of Thermodynamics• When energy is converted from one form to When energy is converted from one form to

another, some of it is degraded to heatanother, some of it is degraded to heat• Heat is highly entropic (disorganized)Heat is highly entropic (disorganized)

• Focus is on qualityFocus is on quality

PhotosynthesisPhotosynthesis

o Biological process by which energy from Biological process by which energy from the sun (radiant energy) is transformed the sun (radiant energy) is transformed into chemical energy of sugar moleculesinto chemical energy of sugar molecules

o Energy captured by plants via Energy captured by plants via photosynthesis is transferred to the photosynthesis is transferred to the organisms that eat the plantsorganisms that eat the plants

6 CO6 CO2 2 + 12 H+ 12 H22O + radiant energyO + radiant energy

CC66HH1212OO66 + 6 H + 6 H22O + 6 OO + 6 O22

Cellular RespirationCellular Respiration

o The process where the chemical energy The process where the chemical energy captured in photosynthesis is released captured in photosynthesis is released within cells of plants and animalswithin cells of plants and animals

o This energy is then used for biological This energy is then used for biological workwork• Creating new cells, reproduction, Creating new cells, reproduction,

movement, etc.movement, etc.

CC66HH1212OO66 + 6 + 6 OO2 2 + 6 H+ 6 H22OO

6 CO6 CO22 + 12 H + 12 H22O + energyO + energy

Energy FlowEnergy Flow

o Passage of Passage of energy in a one-energy in a one-way direction way direction through an through an ecosystemecosystem• ProducersProducers• Primary Primary

consumersconsumers• Secondary Secondary

consumersconsumers• DecomposersDecomposers

Food Chains- The Path of Energy Food Chains- The Path of Energy FlowFlow

o Energy from food passes from one Energy from food passes from one organisms to anotherorganisms to another• Each “link” is called a trophic levelEach “link” is called a trophic level

Food webs represent interlocking food Food webs represent interlocking food chains that connect all organisms in an chains that connect all organisms in an

ecosystemecosystem

Ecological PyramidsEcological Pyramids

o Graphically represent the relative Graphically represent the relative energy value of each trophic levelenergy value of each trophic level• Important feature is that large amount of Important feature is that large amount of

energy are lost between trophic levels to energy are lost between trophic levels to heatheat

o Three main typesThree main types• Pyramid of numbersPyramid of numbers• Pyramid of biomassPyramid of biomass• Pyramid of energyPyramid of energy

Pyramid of NumbersPyramid of Numberso Illustrates the number of organisms at Illustrates the number of organisms at

each trophic leveleach trophic level• Usually, organisms at the base of the Usually, organisms at the base of the

pyramid are more numerouspyramid are more numerous• Fewer organisms occupy Fewer organisms occupy

each successive leveleach successive level

o Do not indicate the Do not indicate the biomass of the organisms biomass of the organisms at each level or the at each level or the amount of energy amount of energy transferred between levelstransferred between levels

Pyramid of BiomassPyramid of Biomasso Illustrates the total biomass at each Illustrates the total biomass at each

successive trophic levelsuccessive trophic level• Biomass: measure of the total amt of living Biomass: measure of the total amt of living

materialmaterial• Biomass indicates the Biomass indicates the

amount of fixed energy amount of fixed energy at a given timeat a given time

o Illustrates a progressive Illustrates a progressive reduction in biomass reduction in biomass through trophic levelsthrough trophic levels

Pyramid of EnergyPyramid of Energyo Illustrates how much energy is present at Illustrates how much energy is present at

each trophic level and how much is each trophic level and how much is transferred to the next leveltransferred to the next level• Most energy dissipates between trophic levelsMost energy dissipates between trophic levels

o Explains why there Explains why there are so few trophic are so few trophic levelslevels• Energy levels get Energy levels get

too low to support too low to support lifelife

Ecosystem ProductivityEcosystem Productivity

o Gross Primary Productivity (GPP)Gross Primary Productivity (GPP)• Total amount of energy that plants capture Total amount of energy that plants capture

and assimilate in a given period of timeand assimilate in a given period of time

o Net Primary Productivity (NPP)Net Primary Productivity (NPP)• Plant growth per unit area per timePlant growth per unit area per time• Represents the rate at which organic Represents the rate at which organic

material is actually incorporated into the material is actually incorporated into the plant tissue for growthplant tissue for growth

o GPP – cellular respiration = NPPGPP – cellular respiration = NPP• Only NPP is available as food to organismsOnly NPP is available as food to organisms

Variation in NPP by EcosystemVariation in NPP by Ecosystem

Human Impact on NPPHuman Impact on NPP

o Humans consume more of earth’s Humans consume more of earth’s resources that any other animalresources that any other animal• Humans represent 0.5% of land-based Humans represent 0.5% of land-based

biomassbiomass• Humans use 32% of land-based NPP!Humans use 32% of land-based NPP!

o This may contribute to loss of species This may contribute to loss of species (extinction)(extinction)

o Humans’ high consumption represents a Humans’ high consumption represents a threat to planet’s ability to support both threat to planet’s ability to support both human and non-human inhabitantshuman and non-human inhabitants