“We must consider our planet to be on loan from our children, rather than being a gift from our ancestors”, G.H. Brundtland (former Prime Minister of Norway)

Community EcologyCampbell Chapters 54-55

(Part I)

LE 54-2

Microorganismsand other

detritivores

Tertiaryconsumers

Secondaryconsumers

Detritus Primary consumers

Sun

Primary producers

Heat

Key

Chemical cycling

Energy flow

LE 53-12

Quaternaryconsumers

Tertiaryconsumers

Carnivore

Carnivore

Carnivore

Carnivore

Secondaryconsumers

CarnivoreCarnivore

Primaryconsumers

ZooplanktonHerbivore

Primaryproducers

PhytoplanktonPlant

A terrestrial food chain A marine food chain

Pyramids of Production• This loss of energy with each transfer in a food

chain– Can be represented by a pyramid of net production

Figure 54.11

Tertiaryconsumers

Secondaryconsumers

Primaryconsumers

Primaryproducers

1,000,000 J of sunlight

10 J

100 J

1,000 J

10,000 J

Production Efficiency• When a caterpillar feeds on a plant leaf

– Only about one-sixth of the energy in the leaf is used for secondary production

Figure 54.10

Plant materialeaten by caterpillar

Cellularrespiration

Growth (new biomass)

Feces 100 J33 J

200 J

67 J

Production Efficiency

Food Web: network of feeding relationships

• In biological magnification– Toxins concentrate at higher trophic levels because

at these levels biomass tends to be lower

Figure 54.23

Conc

entr

ation

of P

CBs

Herringgull eggs124 ppm

Zooplankton 0.123 ppm

Phytoplankton 0.025 ppm

Lake trout 4.83 ppm

Smelt 1.04 ppm

Ecological succession in Massachusetts . . .

• Ferns and Grasses• Shrubs• White pine• Hardwoods (maple,

oak, hickory, and some birches)

• Hemlock and Beech

A. insolitususually percheson shady branches.

A. distichus perches on fence posts and

other sunny surfaces.

A. distichus

A. ricordii

A. insolitus

A. christophei

A. cybotesA. etheridgei

A. alinigar

Figure 53.3

Resource Partitioning• Resource partitioning is the differentiation

of niches – no two species can occupy the same niche.

Community Interactions

• Mimicry• Parasitism• Commensalism• Coevolution (Yucca moth

and Yucca plant)• Predator/prey• Mutualism• Symbiosis• Exotic species

• Cryptic coloration, or camouflage– Makes prey difficult to spot

Figure 53.5

• Aposematic coloration– Warns predators to stay away from prey

Figure 53.6

• In Batesian mimicry– A palatable or harmless species mimics an

unpalatable or harmful model

(a) Hawkmoth larva

(b) Green parrot snake

Figure 53.7a, b

• In Müllerian mimicry– Two or more unpalatable species resemble

each other

(a) Cuckoo bee

(b) Yellow jacketFigure 53.8a, b

Parasitism – one species benefits while the other is harmed Braconid wasps parasitizing a tomato horn worm

• In commensalism– One species benefits and the other is not

affected Ex. Bird nests in trees

Mutualism – both species benefit

Keystone Species

• Keystone species– Are not necessarily abundant in a community– Exert strong control on a community by their

ecological roles, or niches

• Field studies of sea stars– Exhibit their role as a keystone species in intertidal

communities

Figure 53.16a,b

(a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates.

With Pisaster (control)

Without Pisaster (experimental)N

umbe

r of s

peci

es

pres

ent

0

5

10

15

20

1963 ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73

(b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity.

Invasive species!

Artificial corridors

Biogeochemical Cycles

• The water cycle and the carbon cycle

Figure 54.17

Transportover land

Solar energy

Net movement ofwater vapor by wind

Precipitationover ocean

Evaporationfrom ocean

Evapotranspirationfrom land

Precipitationover land

Percolationthroughsoil

Runoff andgroundwater

CO2 in atmosphere

Photosynthesis

Cellularrespiration

Burning offossil fuelsand wood Higher-level

consumersPrimaryconsumers

DetritusCarbon compounds in water

Decomposition

THE WATER CYCLE THE CARBON CYCLE

• The nitrogen cycle and the phosphorous cycle

Figure 54.17

N2 in atmosphere

Denitrifyingbacteria

Nitrifyingbacteria

Nitrifyingbacteria

Nitrification

Nitrogen-fixingsoil bacteria

Nitrogen-fixingbacteria in rootnodules of legumes Decomposers

Ammonification

Assimilation

NH3 NH4+

NO3

NO2

Rain

Plants

Consumption

Decomposition

Geologicuplift

Weatheringof rocks

Runoff

SedimentationPlant uptakeof PO4

3

Soil

Leaching

THE NITROGEN CYCLE THE PHOSPHORUS CYCLE