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Chapter 53. Community Ecology. Community- a group of populations of various species living close enough for potential interaction. How many interactions between species are occurring in this scene?. Competition.

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chapter 53

Chapter 53

Community Ecology

slide2
Community- a group of populations of various species living close enough for potential interaction

How many interactions between species are occurring in this scene?

competition
Competition
  • Competitive exclusion- strong competition can lead to the elimination of a competing species
  • Competitive exclusion principle- two species competing for the same limiting resources cannot coexist in the same place
ecological niches
Ecological Niches
  • Ecological niche- the total of a species’ use of biotic and abiotic resources
  • Resource partitioning- differentiation of ecological niches, enabling similar species to coexist in a community
slide5

A. distichus perches on fence

posts and other sunny surfaces.

A. insolitus usually perches

on shady branches.

Resource partitioning among Dominican Republic lizards

A. ricordii

A. insolitus

A. aliniger

A. christophei

A. distichus

A. cybotes

A. etheridgei

predation
Predation
  • Cryptic coloration (camouflage)- makes prey difficult to spot

Cryptic

coloration

Canyon tree frog

slide7
Aposematic coloration- animals with effective chemical defense often exhibit bright warning coloration

(b)

Poison dart frog

slide8
Batesian mimicry- a harmless species mimics an unpalatable or harmful model

Hawkmoth

larva

Green parrot snake

symbiosis
Symbiosis
  • Parasitism- the parasite derives nourishment from a host which is harmed in the process
  • Mutualism- an interaction that benefits both species
  • Commensalism - one species benefits and the other is apparently unaffected
species diversity
Species Diversity
  • Species Diversity of a community is the variety of organisms that make up the community
  • Species richness- the total number of different species in the community
  • Relative abundance- the proportion each species represents of the total individuals in the community
slide12

A

B

C

D

Community 1

Community 2

A: 80% B: 5% C: 5% D: 10%

A: 25% B: 25% C: 25% D: 25%

trophic structure
Trophic Structure

Trophic Structure- the feeding relationships between organisms in a community

  • Food chains link trophic levels from producers to top carnivores
  • Food web- a branching food chain with complex trophic interactions
slide14

Humans

Quaternary

consumers

Carnivore

Smaller

toothed

whales

Carnivore

Sperm

whales

Baleen

whales

Tertiary

consumers

Carnivore

Carnivore

Elephant

seals

Leopard

seals

Crab-eater

seals

Secondary

consumers

Carnivore

Carnivore

Squids

Fishes

Birds

Primary

consumers

Carnivorous

plankton

Herbivore

Zooplankton

Euphausids

(krill)

Copepods

Primary

producers

Phyto-

plankton

Plant

Phytoplankton

A terrestrial food chain

A marine food chain

slide15
Each food chain in a food web is usually only a few links long
  • Energetic hypothesis- length is limited by inefficient energy transfer
  • Dynamic stability hypothesis- long food chains are less stable than short ones
species with a large impact
Species with a Large Impact
  • Dominant species- those that are most abundant or have the highest biomass
  • Invasive species -introduced to a new environment, often lack predators or disease
  • Keystone species- exert strong control on a community by their ecological roles, or niches
foundation species ecosystem engineers
Foundation Species (Ecosystem “Engineers”)
  • Foundation Species (Ecosystem “Engineers”)- cause physical changes in the environment that affect community structure
ecological succession
Ecological Succession

Ecological succession-the sequence of community and ecosystem changes after a disturbance

  • Primary succession occurs where no soil exists when succession begins
  • Secondary succession begins in an area where soil remains after a disturbance
slide19

Glacial retreat and primary succession at Glacier Bay, Alaska

1941

1907

2

Dryas stage

Pioneer stage, with

fireweed dominant

1

0

5

10

15

Kilometers

1860

Glacier

Bay

Alaska

1760

4

Spruce stage

3

Alder stage

slide20

Fig. 54-22a

Pioneer stage, with fireweed dominant

1

slide24

60

50

40

Soil nitrogen (g/m2)

30

20

10

0

Pioneer

Dryas

Alder

Spruce

Successional stage

area effects
Area Effects
  • Species-area curve- all other factors being equal, a larger geographic area has more species
slide26

Species-area curve for North American breeding birds

1,000

100

Number of species

10

1

0.1

1

10

100

103

104

105

106

107

108

109

1010

Area (hectares)