Lecture AP Biology Chapter 55 Ecosystems

This chapter explain how the first and second laws of thermodynamics apply to ecosystems; define and compare gross primary production, net primary production, and standing crop; explain why energy flows but nutrients cycle within an ecosystem; explain what factors may limit primary production in aquatic ecosystems.

Ch 55 Warm-Up

1 Draw an energy pyramid and

label the following trophic levels:

producers, how much of that

energy would be available to

 Net primary production (NPP)

 Biogeochemical cycle

 Nitrogen fixation

Chapter 55: Ecosystems

You Must Know:

•How energy flows through the ecosystem (food chains and food webs)

•The difference between gross primary

productivity and net primary productivity

•The carbon and nitrogen biogeochemical cycles

Ecosystem = sum of all the organisms living

within its boundaries (biotic community) + abiotic factors with which they interact

Involves two unique processes:

1 Energy flow

2 Chemical cycling

Overview of energy & nutrient dynamics

Energy Flow in an Ecosystem

•Energy cannot be recycled  must be constantly supplied to an ecosystem (mostly by SUNSUN)

•The autotrophs (“self feeders”) are the primary

producers, and are usually photosynthetic (plants

•Heterotrophs are

at trophic levelsabove the primaryproducers and

depend on theirphotosynthetic

output

▫ Herbivores that eat primary producers are

called primary consumers.

▫ Carnivores that eat herbivores are called

 They get energy from detritus, nonliving

organic material, and play an important role

in material cycling.

Main decomposers: fungi & prokaryotes

Primary Production

•Primary production = amt of light energy that

is converted to chemical energy

•Gross primary production (GPP): total primary production in an ecosystem

•Net primary production (NPP) = gross primary production minus the energy used by the

primary producers for respiration (R):

▫NPP = GPP – R

•NPP = storage of chemical energy available to

consumers in an ecosystem

Open ocean Continental shelf

Upwelling zones Extreme desert, rock, sand, ice

Swamp and marsh Lake and stream

Desert and semidesert scrub

Tropical rain forest

Temperate deciduous forest

Temperate evergreen forest

Tropical seasonal forest

Savanna Cultivated land

Estuary Algal beds and reefs

Boreal forest (taiga)

Temperate grassland

Woodland and shrubland

Tundra

0.4 0.4 1.0 1.3 1.5 1.6 1.7 1.8 2.4 2.7 2.9 3.3 3.5 4.7

0.3 0.1 0.1

0 0 500 1,000 1,500 2,000 2,500

Percentage of Earth’s net primary production

25 20 15 10 5 0

900 600 800

2,200

600

250

1,600 1,200 1,300

2,000

700 140

0.3

7.9 9.1 9.6 5.4 3.5 0.6

7.1 4.9 3.8 2.3

24.4

5.6 1.2 0.9 0.1 0.04 0.9

22

Net primary production of different ecosystems

•Primary production affected by:

▫Light availability (↑ depth, ↓ photosynthesis)

▫Nutrient availability (N, P in marine env.)

•Key factors controlling primary production:

▫Temperature & moisture

•A nutrient-rich lake that supports algae growth is

eutrophic

Energy transfer between trophic levels is typically only 10% efficient

•Production efficiency:

only fraction of E stored

in food

•Energy used in

respiration is lost as heat

•Energy flows (not cycle!)

within ecosystems

10% transfer of energy from one level to next

Ecological pyramids give insight to food chains

Matter Cycles in Ecosystem

•Biogeochemical cycles: nutrient cycles that contain both biotic and abiotic components

•organic  inorganic parts of an ecosystem

•Nutrient Cycles: water, carbon, nitrogen,

phosphorus

Water Cycle

Carbon Cycle

• CO2 removed by photosynthesis, added by burning fossil fuels

▫ Absorbed by plants

• Denitrification :

▫ Release N to atmosphere

Phosphorus Cycle

Restoration Ecology

fungi, plants) to detoxify polluted ecosystems

(eg nitrogen-fixers) to add essential nutrients

Bioremediation of groundwater contaminated

with uranium

Restoration ecology projects