Energy Flow and Chemical Cycles

Objectives

• Discuss energy flow through different ecosystems

• Trace cycles of Carbon, Nitrogen, and water

Ecosystem

All the energetic interactions and material cycling that link organisms in a community with one another and with their environment

Energy and Production

Laws of Thermodynamics

Energy is not created or destroyed. It changes form and place

When energy changes form some of it is lost as entropy (heat)

Production

Primary Production = energy accumulated by plants

Gross Primary Production = total photosynthesis

Net Primary Production = energy remaining after Respiration and stored as organic matter.

NPP=GPP-R

Standing crop biomass = accumulated organic matter on a given are at a given time

Difference in productivity

• Species efficiency• Efficiency = NPP/GPP• Corn .85• Deciduous trees .42• Prairie grass .66

• Physical environment– Water

– Heat

Secondary ProductionAnimals

Energy, once consumed goes to maintenance, and waste. Little is left for production.

10% rule .

Homeotherms

High assimilation, high metabolism, thus low production efficiency

Poikilotherms

Low metabolism, low assimilation, thus even lower production efficiency

Food Chains and Food Webs

Definitions

Food Chain– series of steps by which energy stored in plants is passed through an ecosystem

Fig. 5.14

Definitions

• Food web – several interrelated food chains

Fig. 5.15

Components

• Producers – plants

• Herbivores – convert plant tissue into animal tissue

• Carnivores – eat other animals, levels

• Omnivores – eats both plants and animals

Components

• Scavengers – animals that eat dead plant and animal matter

• Saprophytes – plant and fungi that absorb dead material

• Decomposers – everything is a decomposer

Another way of viewing energy relationships

(Heterotrophs)

Biophages – use living matter

Saprophages – use nonliving matter

Two Major Food Chains

• Grazing food chain – energy flows through the biophages

• Detrital food chain – energy flows through the saprophages.

Fig. 23.3

Fig. 23.4

Fig. 23.5

Chemical Cycles

Water cycle

• Fig. 16.3

Water Cycle

Carbon Cycle

• Fig 5.16

Carbon Cycle

Nitrogen cycle

• Fig. 5.17

Nitrogen cycle

The End

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