Producers and Consumers: the Living Components of Ecosystems • BASIC ECOSYSTEM STRUCTURE• Biotic vs. Abiotic• Producers, autotrophs … TROPH = EATING/FEEDING• Photosynthesis: You must know this reaction• CO2 + H2O + sunlight → glucose + oxygen

• Chemosynthesis• Consumers, heterotrophs• Decomposers

Energy Flows Through Ecosystems in Food Chains and Food Webs

• Food chain• Movement of energy and nutrients from one trophic

level to the next … TROPHIC = EATING/FEEDING• FIG 3.13

• Food web• Network of interconnected food chains FIG 3.14

Usable Energy Decreases with Each Link in a Food Chain or Web

•Pyramid of energy flow• 90% of energy lost with each transfer … AS HEAT• Less chemical energy for higher trophic levels• FIG 3.15

Some Ecosystems Produce Plant Matter Faster Than Others Do

FIG 3.16• Gross primary productivity (GPP)• Rate at which producers convert solar energy to

chemical energy and biomass• Kcal/m2/year WHAT IS GROSS INCOME?

• Net primary productivity (NPP)• GPP (above) minus the rate at which producers use

energy for aerobic respiration• Ecosystems and life zones differ in their NPP• WHAT IS NET INCOME?

Estimated Annual Average NPP in Major Life Zones and Ecosystems FIG 3.16

Fig. 3-15, p. 66

Nutrients Cycle in the Biosphere

• Biogeochemical cycles, nutrient cycles• Hydrologic FIG 3.17• Carbon• Nitrogen• Phosphorus• Sulfur

• Nutrients may remain in a reservoir for a period of time

Water Cycles through the Biosphere• Natural renewal of water quality: three major processes

• Evaporation• Precipitation• Transpiration

• Alteration of the hydrologic cycle by humans• Withdrawal of large amounts of freshwater at rates faster than

nature can replace it• Clearing vegetation causing increased runoff• Increased flooding when wetlands are drained

• Special properties of water• Solvent, stays liquid, filters UV rays, expands as it freezes, holds

lots of heat

Carbon Cycle Depends on Photosynthesis and Respiration

• Link between photosynthesis in producers and respiration in producers, consumers, and decomposers

• Additional CO2 added to the atmosphere• Tree clearing• Burning of fossil fuels• Warms the atmosphere

Fig. 3-19, p. 70

Carbon dioxide in atmosphere Respiration

Photosynthesis

Animals (consumers) Burning

fossil fuelsDiffusion Forest fires

Plants (producers)Deforestation

Transportation RespirationCarbon in

plants (producers)

Carbon dioxide dissolved in ocean

Carbon in animals

(consumers)Decomposition

Marine food webs Producers, consumers, decomposers

Carbon in fossil fuels

Carbon in limestone or dolomite sediments

Compaction

Process

Reservoir

Pathway affected by humans

Natural pathway

Nitrogen Cycles through the Biosphere: Bacteria in Action (1)

• Nitrogen fixed by lightning• Nitrogen fixed by bacteria and cyanobacteria• Combine gaseous nitrogen with hydrogen to make

ammonia (NH3) and ammonium ions (NH4+)

• Nitrification • Soil bacteria change ammonia and ammonium ions to

nitrate ions (NO3-)

• Denitrification• Nitrate ions back to nitrogen gas

Nitrogen Cycles through the Biosphere: Bacteria in Action (2)

• Human intervention in the nitrogen cycle1. Additional NO and N2O in atmosphere from burning

fossil fuels; also causes acid rain2. N2O to atmosphere from bacteria acting on

fertilizers and manure3. Destruction of forest, grasslands, and wetlands4. Add excess nitrates to bodies of water5. Remove nitrogen from topsoil

Nitrogen Cycle in a Terrestrial Ecosystem with Major Harmful Human Impacts

Fig. 3-20, p. 71

Fig. 3-20, p. 71

ProcessNitrogen in atmosphere

Denitrification by bacteriaReservoirNitrification by bacteriaPathway affected by humans

Natural pathwayNitrogen in

animals (consumers)Nitrogen oxides

from burning fuel and using inorganic fertilizers

Volcanic activity

Electrical storms

Nitrogen in plants

(producers)

DecompositionNitrates from

fertilizer runoff and

decompositionUptake by plants

Nitrate in soil

Nitrogen loss to deep ocean sediments

Nitrogen in ocean sediments

Bacteria

Ammonia in soil

Human Input of Nitrogen into the Environment

Supplement 9, Fig 16

Phosphorus Cycles through the Biosphere

• Cycles through water, the earth’s crust, and living organisms

• Limiting factor for plant growth

• Impact of human activities1. Clearing forests2. Removing large amounts of phosphate from the

earth to make fertilizers3. Erosion leaches phosphates into streams

Phosphorus Cycle with Major Harmful Human Impacts

Fig. 3-21, p. 73

Fig. 3-21, p. 73

ProcessReservoir

Pathway affected by humansNatural pathway

Phosphates in sewage

Phosphates in fertilizer Plate

tectonicsPhosphates in mining waste RunoffRunoff

Sea birds

RunoffPhosphate in rock (fossil bones, guano)

ErosionOcean food webs

Animals (consumers) Phosphate

dissolved in water

Phosphate in shallow ocean sediments

Phosphate in deep ocean sediments

Plants (producers)

Bacteria

Sulfur Cycles through the Biosphere• Sulfur found in organisms, ocean sediments, soil, rocks, and

fossil fuels

• SO2 in the atmosphere

• H2SO4 and SO4-

• Human activities affect the sulfur cycle• Burn sulfur-containing coal and oil• Refine sulfur-containing petroleum• Convert sulfur-containing metallic mineral ores

Natural Capital: Sulfur Cycle with Major Harmful Impacts of Human Activities

Fig. 3-22, p. 74

Fig. 3-22, p. 74

Sulfur dioxide in atmosphere

Sulfuric acid and Sulfate deposited as acid rain

Smelting Burning coal

Refining fossil fuels

Dimethyl sulfide a bacteria byproduct

Sulfur in animals

(consumers)

Sulfur in plants

(producers)Mining and extraction Uptake

by plantsSulfur in ocean sediments

Decay

Decay

Process Sulfur in soil, rock

and fossil fuelsReservoirPathway affected by humansNatural pathway

Three Big Ideas

1. Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.

2. Some organisms produce the nutrients they need, others survive by consuming other organisms, and some recycle nutrients back to producer organisms.

3. Human activities are altering the flow of energy through food chains and webs and the cycling of nutrients within ecosystems and the biosphere.