Eco Sy Ste Ms

Eco sy ste ms Chapter 48

Ecosystem  An association of organisms and their  physical environment, interconnected  by  ongoing flow of energy and a  cycling of materials

Mo des of N utr ition  Autotrophs  Capture sunlight or chemical energy  Producers

 Heterotrophs  Extract energy from other organisms or organic wastes  Consumers, decomposers, detritivores

Sim ple Ec osyst em Mo del

energy input from sun

PHOTOAUTOTROPHS (plants, other producers)

nutrient cycling

HETEROTROPHS (consumers, decomposers)

energy output (mainly heat)

Co nsu me rs  Herbivores  Carnivores

SPRING

fruits insects

rodents, rabbits

birds

 Parasites  Omnivores  Decomposers  Detritivores

SUMMER

fruits rodents, rabbits

insects birds

Seasonal variation in the diet of an omnivore (red fox)

Tr ophic Levels  All the organisms at a trophic level are the same number of steps away from the energy input into the system  Producers are closest to the energy input and are the first trophic level

Tr ophic Levels in Pr air ie 5th

4th

Fourth-level consumers (heterotrophs): Top carnivores, parasites, detritivores, decomposers

Third-level consumers (heterotrophs): Carnivores, parasites, detritivores, decomposers Second-level consumers (heterotrophs):

3rd

Carnivores, parasites, detritivores, decomposers First-level consumers (heterotrophs):

2nd Herbivores, parasites, detritivores, decomposers Primary producers (autotrophs): 1st

Photoautotrophs, chemoautotrophs

Food Chain MARSH HAWK

 A straight line sequence of who

UPLAND SANDPIPER

eats whom  Simple food chains are rare in nature

GARTER SNAKE

CUTWORM

Food We b

Energy Losses    Energy transfers are never 100  percent efficient  Some energy is lost at each step  Limits the number of trophic levels in  an ecosystem  

Grazing Food Web

Detrital Food Web

Tw o Typ es o f Food Webs Producers (photosynthesizers)

Producers (photosynthesizers)

herbivores

decomposers

carnivores

detritivores

decomposers

ENERGY OUTPUT

ENERGY OUTPUT

Biological Magnification   A nondegradable or slowly degradable  substance becomes more and more  concentrated in the tissues of  organisms at higher trophic levels of a  food web

DDT in F ood Webs  Synthetic pesticide banned in the United States since the 1970s  Birds that were top carnivores accumulated DDT in their tissues

Bio accumu latio n

Primary Productivity  Gross primary productivity is  ecosystem’s total rate of  photosynthesis  Net primary productivity is rate at  which producers store energy in 

Pr ima ry Pr oductivity Va rie s  Seasonal variation  Variation by habitat  The harsher the environment, the slower plant growth, the lower the primary productivity

Silver Springs Study  Aquatic ecosystem in Florida  Site of a long­term study of a grazing food web Biomass pyramid

decomposers, detritivores 5 (bacteria, crayfish)

1.5

third-level carnivores (gar, large-mouth bass)

1.1

second-level consumers (fishes, invertebrates)

37

first-level consumers (herbivorous fishes, turtles, invertebrates)

809

primary producers (algae, eelgrass, rooted plants)

Pyr amid of En ergy Flo w  Primary producers trapped about 1.2 percent of the solar energy that entered the ecosystem  6-16% passed on to next level

top carnivores

21

carnivores herbivores

383

decomposers

3,368 producers

20,810 kilocalories/square meter/year

detritivores

All He at in th e End  At each trophic level, the bulk of the energy received from the previous level is used in metabolism  This energy is released as heat energy and lost to the ecosystem  Eventually, all energy is released as heat

Biogeochemical Cycle  The flow of a nutrient from the  environment to living organisms and  back to the environment  Main reservoir for the nutrient is in the  environment

Th ree Ca tegories  Hydrologic cycle  Water

 Atmospheric cycles  Nitrogen and carbon

 Sedimentary cycles  Phosphorus and sulfur

Hyd ro logic Cyc le Atmosphere

wind driven water vapor 40,000

evaporation from ocean 425,000

precipitation into ocean 385,000

precipitation onto land 111,000

evaporation from land plants (evapotranspiratio n) 71,000 surface and groundwater flow 40,000

Oceans

Land

Hubbard Br ook Ex periment  A watershed was experimentally stripped of vegetation  All surface water draining from watershed was measured  Removal of vegetation caused a six-fold increase in the calcium content of the runoff water

Hubbard Br ook Ex periment losses from disturbed watershed

time of deforestation losses from undisturbed watershed

Phosphorus Cycle  Phosphorus is part of phospholipids  and all nucleotides  It is the most prevalent limiting factor in  ecosystems   Main reservoir is Earth’s crust; no  gaseous phase

Ph osphorus Cyc le

mining excretion

FERTILIZER

GUANO agriculture uptake by autotrophs

MARINE FOOD WEBS

weathering

DISSOLVED IN OCEAN WATER

uptake by autotrophs weathering

DISSOLVED IN SOILWATER, LAKES, RIVERS

death, decomposition sedimentation

death, decomposition leaching, runoff

setting out

MARINE SEDIMENTS

uplifting over geolgic time

ROCKS

LAND FOOD WEBS

Huma n Ef fects  In tropical countries, clearing lands for agriculture may deplete phosphoruspoor soils  In developed countries, phosphorus runoff is causing eutrophication of waterways

Carbon Cycle  Carbon moves through the  atmosphere and food webs on its way  to and from the ocean, sediments, and  rocks  Sediments and rocks are the main  reservoir

Ca rbon Cyc le diffusion

Atmosphere

Bicarbonate,  volcanic action carbonate Marine food  TERRESTRIAL webs ROCKS

Marine Sediments weathering

Terrestrial Rocks photosynthesis

Soil Water

Land Food  Webs Peat, Fossil  Fuels

Ca rbon in th e Oc eans  Most carbon in the ocean is dissolved carbonate and bicarbonate  Ocean currents carry dissolved carbon

Ca rbon in At mo sphere  Atmospheric carbon is mainly carbon dioxide  Carbon dioxide is added to atmosphere  Aerobic respiration, volcanic action, burning fossil fuels

 Removed by photosynthesis

Greenhouse Effect  Greenhouse gases impede the escape  of heat from Earth’s surface

Global Wa rm in g  Long-term increase in the temperature of Earth’s lower atmosphere

Ca rbon Dioxide Increase  Carbon dioxide levels fluctuate seasonally  The average level is steadily increasing  Burning of fossil fuels and deforestation are contributing to the increase

Oth er Gr eenhouse Gase s  CFCs - synthetic gases used in plastics and in refrigeration  Methane - produced by termites and bacteria and cow burps  Nitrous oxide - released by bacteria, fertilizers, and animal wastes

St ore L iq uid CO 2 o n Ocean Bo ttom?  “At shallow depths liquid carbon dioxide will rise to the surface. But based on laboratory experiments with carbon dioxide hydrates, researchers imagined that liquid carbon dioxide put deep in the ocean would form a stable layer on the seafloor with a skin of solid hydrate as a boundary, like a pond covered by ice in winter.” from the Monterey Bay http://www.cnn.com/NATURE/9905/10/oceans.enn/ Aquarium Research Institute

Nitrogen Cycle  Nitrogen is used in amino acids and  nucleic acids  Main reservoir is nitrogen gas in the  atmosphere

Nit rogen Cyc le GASEOUS NITROGEN (N2) IN ATMOSPHERE

NITROGEN FIXATION by industry for agriculture

FOOD WEBS ON LAND

FERTILIZERS

NITROGEN FIXATION

uptake by autotrophs

excretion, death, decomposition NITROGENOUS WASTES, REMAINS IN SOIL

NH3-, NH4+ IN SOIL

AMMONIFICATION

loss by leaching

1. NITRIFICATION

uptake by autotrophs

NO3IN SOIL

2. NITRIFICATION

NO2IN SOIL

loss by leaching

Nitrogen F ix atio n  Plants cannot use nitrogen gas  Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NH3)  Ammonia and ammonium can be taken up by plants

Dia zo trophs  Soil bacteria that fix nitrogen  Most famous: Rhizobia  Rhizobia lives in a symbiotic relationship with legumes

Nitrogen F ix atio n vid eo

 http://www.youtube.com/watch?v=k3TrdF-P

NH 4

+

to NO 3

- Nitrofication

 “Nitrification is the biological oxidation of ammonia with oxygen into nitrite  Followed by the oxidation of these nitrites into nitrates  Nitrification is an important step in the nitrogen cycle in soil “  Important bacteria: Nitrosomonas and Nitrobacter

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

Se a Ba tt le So uth Am erica

Am mo nific atio n & Nitrific atio n  Bacteria and fungi carry out ammonification, conversion of nitrogenous wastes to ammonia  Nitrifying bacteria convert ammonium to nitrites and nitrates

Nitrogen L oss  Nitrogen is often a limiting factor in ecosystems  Nitrogen is lost from soils via leaching and runoff  Denitrifying bacteria convert nitrates and nitrites to nitrogen gas (often occurs in water logged soil)

Huma n Ef fects  Humans increase rate of nitrogen loss by clearing forests and grasslands  Humans increase nitrogen in water and air by using fertilizers and by burning fossil fuels  Too much or too little nitrogen can compromise plant health

Sew age spi ll hi ts Peachtree Creek, Cha ttahoochee

 Over a million gallons of raw sewage poured into a creek Monday just upstream of the Chattahoochee River and near the spot where Atlanta draws its drinking water.  Before a collapsed 36-inch sewer pipe was repaired, sewage flowed into Peachtree Creek at the rate of 10,000 gallons a minute for two hours, said Janet Ward, a spokeswoman for Atlanta's Watershed Management Department. The incident occurred

near the Chattahoochee Water Treatment Plant off Bolton Road, where the city gets drinking water.

The Atlanta Journal-Constitution Published on: 11/29/05

Dead Waters Massive oxygen-starved zones are developing along the world's coasts

 “Summer tourists cruising the waters off Louisiana or Texas in the Gulf of Mexico take in gorgeous vistas as they pull in red snappers and blue marlins. Few realize that the lower half of the water column below them may lack fish, despite the piscine bounty near the surface.”

Ni trates and Phosphates Con tri butio ns f ro m Ferti lizer s  “Typically, they appear where a river spews rich plumes of nutrients into water that's stratified because of either temperature or salinity differences between the bottom and the top of the water column. If the water doesn't mix, oxygen isn't replenished in the lower half.”

Eu trophicatio n L eads to Oxyg en Deple tion

Ba cte ria Use Up Most of th e O 2  “the Mississippi River deposits water that is heavily enriched with plant nutrients, principally nitrate. This pollutant fertilizes the abundant growth of tiny, floating algae. As blooms of the algae go through their natural life cycles and die, they fall to the bottom and create a feast for bacteria. Growing in unnatural abundance, the bacteria use up most of the oxygen from the bottom water.” http://www.sciencenews.org/articles/20040605/bob9.asp

Bla ck Se a