1

Ecosystems/ Ecological ProcessesI. Factors that Influence Ecosystem

A. Limiting factors1. Abiotic Factors2. Biotic Factor Competition: interspecific and intraspecificPredation/ParasitismAmensalismMutualism

II. Biotic Structure of the EcosystemA. Food ChainsB. Trophic Levels

Some definitions Biosphere: all living organisms and their environment

Ecosystem: grouping of plants, animals and microbes, etc. interacting with each other and their physical environment "ECO" = home

Community: all plants and animals inhabiting an area (suggests interactions)

Population: a group of individuals of the same species in an area

Species: a group of organisms where all members do or have the potential to interbreed and produce viable offspring

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The Nature of Ecology

Organisms

Populations

Communities

Ecosystems

Biosphere

BiosphereBiosphere

Ecosystems

Communities

Populations

Organisms

Fig. 4.2, p. 72

Factors that Influence Ecosystems

Limiting Factors: anything that tends to make it more difficult for a species to live and grow, or reproduce in its environment.

Abiotic and Biotic: physical and biological factors can work in concert.

ToleranceThe degree a certain factor that an

organism can withstand is called tolerance.

• Optimum temperature• Range of tolerance• Limit of tolerance• Env. gradients

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Limiting Factors: Env. gradientsRange of optimum

Popu

lation

size

Low High Temperature

Zone ofintolerance

Zone ofphysiological stress

Optimum range Zone ofphysiological stress

Zone ofintolerance

Noorganisms

Feworganisms

Lower limitof tolerance

Abundance of organismsFew

organismsNo

organisms

Upper limitof tolerance

ABIOTIC Limiting Factors

temperature water climate/weather soils (mineral component) terrainfire

BIOTIC Limiting Factors

competition:interspecific and intraspecific

predation/parasitismamensalismmutualism

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BIOTIC Limiting Factors

competition:interspecific and intraspecific

Types of competition• Intraspecific (social behavior)

– Territoriality– Social hierarchy

• Interspecific– Competitive exclusion– Predator prey interactions– Parasitism– Amensalism– Mutualism

Intraspecific(social behavior)

TerritorialitySocial hierarchy

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Avoiding/Reducing Competition

• Behavioral specializations

Social hierarchy

Impalas: harem society

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Familial groups

Matriarchal societies

Matrilineal societies

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Agama sp.

Color changes to indicate

dominant individuals

• Avoiding intraspecific competition– SPATIAL OR TEMPORAL SEPARATION

Avoiding/Reducing Competitionby temporal separation

Ex: Kenya:

African Savanah

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Wildebeest and zebra

wildebeest

topis

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gazelles

• Feeding specializations

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Predatory birds

Interspecific Competition

• Competitive exclusion• Predator prey interactions• Parasitism• Amensalism• Mutualism

• Bromus tectorum

European starling

Competitive exclusion

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Zebra mussels

Predator prey interactions

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Fig. 9.8, p. 203

Popu

lation

size

(tho

usan

ds)

160

140

120

100

80

60

40

20

01845 1855 1865 1875 1885 1895 1905 1915 1925 1935

Year

Hare

Lynx

5,000

4,000

3,000

2,000

1,000

500

Num

ber

of m

oose

1009080706050403020100

1900 1910 1930 1950 1970 1990 2000

1997Year

Num

ber of wolvesMoose population

Wolf population

Parasitism

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Amensalism

Mutualism

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