Ecosystems

Ecosystems

EcosystemsAn ecosystem is all of the organisms in an An ecosystem is all of the organisms in an area, along with their nonliving environmentarea, along with their nonliving environment

Example: aquariumExample: aquariumLiving + Non-livingLiving + Non-living(Biotic + Abiotic)(Biotic + Abiotic)

Trophic LevelsOrganisms in a Organisms in a community are related community are related to each other through to each other through feeding relationshipsfeeding relationshipsEach step up in the Each step up in the transfer of energy is transfer of energy is known as a known as a trophic trophic levellevelAll energy ultimately All energy ultimately comes from the comes from the SUNSUN

Trophic LevelsDecomposers/ Decomposers/ DetritivoresDetritivores

Eat detritus (organic Eat detritus (organic waste/remains of waste/remains of dead organisms)dead organisms)Can fit in to a food Can fit in to a food chain or web at any chain or web at any locationlocation

Trophic Levels

ProducersProducersConvert solar (or Convert solar (or chemical) energy into chemical) energy into organic compounds organic compounds

Primary consumersPrimary consumersEat producersEat producers

Secondary consumersSecondary consumersEat primary consumersEat primary consumers

Tertiary consumersTertiary consumersEat secondary consumersEat secondary consumers

Pyramid of Numbers/Biomass/Energy

Numbers, Numbers, energy, & energy, & biomass biomass decreases as one decreases as one moves up the moves up the food chain.food chain.Biomass- dry Biomass- dry mass of organic mass of organic mattermatter

Trophic LevelsTen-Percent LawTen-Percent Law

UsableUsable energy is lost through each transfer of energy energy is lost through each transfer of energyWhy? (Remember the law of conservation of energy says energy Why? (Remember the law of conservation of energy says energy cannot be created or destroyed; it only changes form.)cannot be created or destroyed; it only changes form.)

Only about 10% of the energy at one trophic level is transferred Only about 10% of the energy at one trophic level is transferred to the next trophic level. 90% is lost as heat with each transfer.to the next trophic level. 90% is lost as heat with each transfer.

Food Chain

A straight-line A straight-line sequence of who sequence of who eats whom eats whom

Simple food Simple food chains are rare in chains are rare in naturenature

marsh hawk

upland sandpiper

garter snake

cutworm

plants

Tall-Grass Prairie Food Web

earthworms, insects

sparrow

vole pocketgopher

groundsquirrel

coyotebadgerweasel

spider

frog

snake

sandpiper crow

marsh hawk

grasses, composites

Primary ProductivityPrimary Productivity:Primary Productivity:

The amount of light energy converted to sugars by The amount of light energy converted to sugars by autotrophs in an ecosystemautotrophs in an ecosystemGross vs. Net Primary ProductivityGross vs. Net Primary Productivity

GPP: the amount of light energy that is converted to GPP: the amount of light energy that is converted to chemical energy by photosynthesis per unit timechemical energy by photosynthesis per unit timeNPP: GPP minus the energy used by the primary NPP: GPP minus the energy used by the primary producers for cellular respirationproducers for cellular respiration

GPP-R=NPPGPP-R=NPP

Limiting NutrientsWhat limits primary production?What limits primary production?

Aquatic EcosystemsAquatic Ecosystems• Light (depth penetration)Light (depth penetration)• NitrogenNitrogen• PhosphorusPhosphorus

– Terrestrial EcosystemsTerrestrial Ecosystems• TemperatureTemperature• MoistureMoisture• Minerals (N & P are the main limiting factors for plants.)Minerals (N & P are the main limiting factors for plants.)

Biogeochemical Cycle• The flow of a nutrient from the environment to living The flow of a nutrient from the environment to living

organisms and back to the environmentorganisms and back to the environment

• Main reservoir for the nutrient is in the environmentMain reservoir for the nutrient is in the environment

Hydrologic CycleAtmosphere

Ocean Land

evaporation from ocean

425,000

precipitation into ocean 385,000

evaporation from land plants (evapotranspiration)

71,000

precipitation onto land 111,000

wind-driven water vapor40,000

surface and groundwater flow 40,000

Figure 48.14Page 876

Figure 48.16 Page 878

diffusion between atmosphere and ocean

bicarbonate and carbonate in ocean water

marine food webs

marine sediments

combustion of fossil fuels

incorporation into sediments

death, sedimentation uplifting

sedimentation

photosynthesis aerobic respiration

Carbon Cycle - Marine

Carbon Cycle - Land

photosynthesis aerobic respirationterrestrial

rocks

soil water

land food webs

atmosphere

peat, fossil fuels

combustion of wood

sedimentation

volcanic action

death, burial, compaction over geologic time

leaching, runoff

weathering

combustion of fossil fuels


Carbon in Atmosphere• Atmospheric carbon is mainly carbon Atmospheric carbon is mainly carbon

dioxidedioxide• Carbon dioxide is added to atmosphereCarbon dioxide is added to atmosphere

– Aerobic respiration, volcanic action, Aerobic respiration, volcanic action, burning fossil fuels burning fossil fuels

• Removed by photosynthesisRemoved by photosynthesis

Greenhouse Effect• Greenhouse gases impede the escape of heat from Greenhouse gases impede the escape of heat from

Earth’s surfaceEarth’s surface

Figure 48.18, Page 880

Global WarmingLong-term increase in the temperature of Long-term increase in the temperature of

Earth’s lower atmosphereEarth’s lower atmosphere


Nitrogen Cycle• Nitrogen is used in amino acids and nucleic Nitrogen is used in amino acids and nucleic

acidsacids

• Main reservoir is nitrogen gas in the Main reservoir is nitrogen gas in the atmosphereatmosphere

Nitrogen Cyclegaseous nitrogen (N2)

in atmosphere

NO3-

in soil

nitrogen fixationby industry

fertilizers

NH3-,NH4+

in soil

1. Nitrification leaching

uptake by autotrophs

excretion, death, decomposition

uptake by autotrophs

nitrogen fixation

leaching

ammonification 2. Nitrification

dentrification nitrogenous

wastes, remains

NO2-

in soil

food webs on land


Nitrogen Fixation• Plants cannot use nitrogen gasPlants cannot use nitrogen gas

• Nitrogen-fixing bacteria convert Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NHnitrogen gas into ammonia (NH33))

• Ammonia and ammonium can be Ammonia and ammonium can be taken up by plantstaken up by plants

Ammonification & Nitrification• Bacteria and fungi carry out ammonificationBacteria and fungi carry out ammonification

– conversion of nitrogenous wastes to ammoniaconversion of nitrogenous wastes to ammonia

• Nitrifying bacteria convert ammonium to nitrites Nitrifying bacteria convert ammonium to nitrites and nitratesand nitrates

Nitrogen Loss• Nitrogen is often a limiting factor in ecosystemsNitrogen is often a limiting factor in ecosystems

• Nitrogen is lost from soils via leaching and Nitrogen is lost from soils via leaching and runoff runoff

• Denitrifying bacteria convert nitrates and Denitrifying bacteria convert nitrates and nitrites to nitrogen gasnitrites to nitrogen gas

Phosphorus Cycle• Phosphorus is part of phospholipids and all Phosphorus is part of phospholipids and all

nucleotidesnucleotides

• It is the most prevalent limiting factor in ecosystems It is the most prevalent limiting factor in ecosystems

• Main reservoir is Earth’s crust; no gaseous phaseMain reservoir is Earth’s crust; no gaseous phase

Phosphorus Cycle

GUANOFERTILIZER

TERRESTRIAL ROCKS

LAND FOOD WEBS

DISSOLVED IN OCEAN

WATER

MARINE FOOD WEBS

MARINE SEDIMENTS

excretion

weathering

mining

agricultureuptake

by autotrophs

death, decomposition

sedimentationsettling

out leaching, runoff

weathering

uplifting

over geologic time

DISSOLVED IN SOILWATER,

LAKES, RIVERS

uptake by

autotrophs

death, decomposition


Human Impact on Ecosystems

• Increased Eutrophication of Increased Eutrophication of LakesLakes– Increase in nutrient levels Increase in nutrient levels

(phosphates, nitrates, etc.)(phosphates, nitrates, etc.)• Can lead to algal bloomsCan lead to algal blooms

– Hypoxia Hypoxia » What is it?What is it?» Why?Why?

• Can lead to the eventual loss of Can lead to the eventual loss of fish and other aquatic organismsfish and other aquatic organisms

• Accelerated by sewage/factory Accelerated by sewage/factory wastes, leaching of fertilizers wastes, leaching of fertilizers into freshwaterinto freshwater

Human Impact on Ecosystems

• Combustion of Fossil Combustion of Fossil FuelsFuels– Leads to acid Leads to acid

precipitationprecipitation– Changes the pH of Changes the pH of

aquatic ecosystems aquatic ecosystems and affects the soil and affects the soil chemistry of chemistry of terrestrial ecosystemsterrestrial ecosystems

Human Impact on Ecosystems• Biological MagnificationBiological Magnification

– Toxins become more Toxins become more concentrated as they move concentrated as they move up the food chainup the food chain• Toxins that are lipophilic cannot Toxins that are lipophilic cannot

be excreted in urine (water!), be excreted in urine (water!), so they are stored in fatty so they are stored in fatty tissue (adipose tissue) unless tissue (adipose tissue) unless the organism has enzymes to the organism has enzymes to break it down break it down

• Important examples?Important examples?– The biomass at any given The biomass at any given

trophic level is produced trophic level is produced from a much larger biomass from a much larger biomass ingested from the level ingested from the level belowbelow

Human Impact on Ecosystems• Increasing Carbon Dioxide Concentration in Increasing Carbon Dioxide Concentration in

the Atmospherethe Atmosphere– Burning fossil fuels (wood, coal, oil) releases COBurning fossil fuels (wood, coal, oil) releases CO22

– Carbon dioxide and water in the atmosphere Carbon dioxide and water in the atmosphere retain solar heat, causing the retain solar heat, causing the greenhouse effectgreenhouse effect

Human Impact on Ecosystems• Use of chlorofluorocarbons has destroyed Use of chlorofluorocarbons has destroyed

ozone (Oozone (O33) by converting it to oxygen gas.) by converting it to oxygen gas.

• Ozone protects against UV radiationOzone protects against UV radiation– Increasing skin cancers, cataractsIncreasing skin cancers, cataracts– What are your odds of getting skin cancer in What are your odds of getting skin cancer in

your lifetime?your lifetime?

Rain ShadowAir rises on the windward side, loses Air rises on the windward side, loses

moisture before passing over the moisture before passing over the mountain Leeward side is in the mountain Leeward side is in the rainshadow; desertsrainshadow; deserts

Figure 49.7Page 893

Biomes• Regions of land characterized by habitat Regions of land characterized by habitat

conditions and community structureconditions and community structure

• Distinctive biomes prevail at certain Distinctive biomes prevail at certain latitudes and elevationslatitudes and elevations

Tropical Forests• May be dry, deciduous, or rainforestsMay be dry, deciduous, or rainforests• T. RainforestT. Rainforest

– Abundant rainfallAbundant rainfall• 4 layers to forest (upper & lower canopy, shrub 4 layers to forest (upper & lower canopy, shrub

understory, & herbaceous layer)understory, & herbaceous layer)• Poor soil due to leachingPoor soil due to leaching• Highest species diversityHighest species diversity

Grasslands• SavannasSavannas

– Tropical & subtropical with scattered treesTropical & subtropical with scattered trees– 3 seasons: cool & dry; hot & dry; warm wet.3 seasons: cool & dry; hot & dry; warm wet.– Frequent firesFrequent fires– Grazing mammalsGrazing mammals– (African grasslands)(African grasslands)

Chaparral• Along coastlines in mid latitudesAlong coastlines in mid latitudes• Mild, rainy winters & hot, dry summersMild, rainy winters & hot, dry summers• Evergreen shrubsEvergreen shrubs• Periodic firesPeriodic fires• Browsers, rodents reptilesBrowsers, rodents reptiles

Temperate Grassland (Prairie)

• Similar to savannah without treesSimilar to savannah without trees• Cold wintersCold winters• Maintained by fireMaintained by fire• Seasonal droughtSeasonal drought• Rich soilsRich soils• Grazing animals; herbivoresGrazing animals; herbivores

Temperate Deciduous Forest• Our biomeOur biome• 3 layered forest3 layered forest• Dominant species are deciduous treesDominant species are deciduous trees• MidlatitudesMidlatitudes

Deserts• Less than 10 centimeters annual rainfall, high Less than 10 centimeters annual rainfall, high

level of evaporationlevel of evaporation

• Tend to occur at 30 degrees north and south Tend to occur at 30 degrees north and south

and in rain shadowsand in rain shadows

• One-third of land surface is arid or semiaridOne-third of land surface is arid or semiarid

Arctic Tundra• Occurs at high Occurs at high latitudeslatitudes

• Permafrost lies Permafrost lies beneath surface beneath surface

• Nutrient cycling is very Nutrient cycling is very slowslow

• Coldest biomeColdest biome

• Low species diversityLow species diversity

Do not post on Internet

Arctic tundra in Russia in summer


Taiga (coniferous forest)• Found in northern latitudesFound in northern latitudes• Harsh winters; short summersHarsh winters; short summers• Thin, acidic soilThin, acidic soil• Coniferous treesConiferous trees• No permafrostNo permafrost

Alpine Tundra• Occurs at high Occurs at high

elevationselevations• No underlying No underlying

permafrostpermafrost• Plants are low cushions Plants are low cushions

or mats as in Arctic or mats as in Arctic tundratundra Do not post

on Internet


Lakes• Bodies of standing freshwater Eutrophic: Bodies of standing freshwater Eutrophic:

shallow, nutrient-rich, has high primary shallow, nutrient-rich, has high primary productivity, Oligotrophic: deep, nutrient-productivity, Oligotrophic: deep, nutrient-poor, has low primary productivitypoor, has low primary productivity

LITTORALLIMNETIC

LITTORAL

PROFUNDAL Figure 49.21Page 904

Lake Zonation

Thermal Layering• In temperate-zone lakes, water can form In temperate-zone lakes, water can form

distinct layers during summerdistinct layers during summer

THERMOCLINE


Seasonal Overturn• In spring and fall, temperatures in the lake In spring and fall, temperatures in the lake

become more uniformbecome more uniform

• Oxygen-rich surface waters mix with deeper Oxygen-rich surface waters mix with deeper oxygen-poor layersoxygen-poor layers

• Nutrients that accumulated at bottom are Nutrients that accumulated at bottom are brought to the surfacebrought to the surface

Ocean Provincesneritic zone

oceanic zone

intertidal zone

BENTHIC PROVINCE

PELAGIC PROVINCE

0200

1,0002,000

4,000

11,0000 depth (meters)

continental shelf

bathyal shelf

abyssal zone

hadal zone

deep-sea trenches

sunlit water

"twilight" w

ater

sunless water


Phytoplankton• Floating or weakly swimming Floating or weakly swimming

photoautotrophs; form the base for most photoautotrophs; form the base for most oceanic food websoceanic food webs

• Ultraplankton are photosynthetic bacteriaUltraplankton are photosynthetic bacteria

Hydrothermal Vents• Openings in ocean floor that Openings in ocean floor that

spew mineral-rich, spew mineral-rich, superheated watersuperheated water

• Primary producers are Primary producers are chemoautotrophic bacteria; chemoautotrophic bacteria; use sulfides as energy use sulfides as energy source source

Tube worms at hydrothermal vent



Estuary•

• Partially enclosed area where saltwater and Partially enclosed area where saltwater and

freshwater mixfreshwater mix

• Dominated by salt-tolerant plantsDominated by salt-tolerant plants

• Examples are Chesapeake Bay, San Examples are Chesapeake Bay, San

Francisco Bay, salt marshes of New England Francisco Bay, salt marshes of New England

Estuarine Food Webs• Primary producers are phytoplankton and salt-Primary producers are phytoplankton and salt-

tolerant plantstolerant plants

• Much primary production enters detrital food Much primary production enters detrital food webswebs

• Detritus feeds bacteria, nematodes, snails, Detritus feeds bacteria, nematodes, snails, crabs, fishcrabs, fish

Intertidal Zones• Littoral zone is submerged only during highest Littoral zone is submerged only during highest

tides of the yeartides of the year

• Midlittoral zone is regularly submerged and Midlittoral zone is regularly submerged and exposedexposed

• Lower littoral is exposed only during lowest Lower littoral is exposed only during lowest tides of the yeartides of the year

Rocky Intertidal

• Grazing food webs Grazing food webs prevailprevail

• Vertical zonation is Vertical zonation is readily apparentreadily apparent

• Diversity is greatest in Diversity is greatest in lower littoral zonelower littoral zone



UpwellingUpward movement of Upward movement of

water along a coast; water along a coast; replaces surface replaces surface waters that move waters that move away from shoreaway from shore


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Ecosystems