Ecological PrinciplesEcological Principles

Part IIPart II

PaCES/HIMB Summer Program in Environmental ScienceDavid A. Krupp, Ph.D

PaCES/HIMB Summer Program in Environmental ScienceDavid A. Krupp, Ph.D

Topics to be StudiedTopics to be Studied Competition between species Predator-prey relationships Symbiosis Species diversity Trophic relationships Ecological succession Productivity Energy flow Biogeochemical cycles

Competition between species Predator-prey relationships Symbiosis Species diversity Trophic relationships Ecological succession Productivity Energy flow Biogeochemical cycles

Competition Among SpeciesCompetition Among Species

Ecological Niche ConceptEcological Niche Concept Ecological niche = the "role" a

species "plays" in the ecosystem. Contrast the ecological niche with the

"habitat" which is the physical environment in which the organism lives.

Ecological niche = the "role" a species "plays" in the ecosystem.

Contrast the ecological niche with the "habitat" which is the physical environment in which the organism lives.

Ecological Niche ConceptEcological Niche Concept The ecological niche of a species,

therefore, includes not just the species’ habitat, but also the ways in which it interacts with other species and the physical environment.

The ecological niche of a species, therefore, includes not just the species’ habitat, but also the ways in which it interacts with other species and the physical environment.

Competitive Exclusion Principle

Competitive Exclusion Principle

No two similar species occupy the same niche at the same time

No two similar species occupy the same niche at the same time

Possible Outcomes of Competition

Possible Outcomes of Competition

Extinction of one species Resource partitioning: splitting the

niche Character displacement: two similar

species evolve in such a way as to become different from each other by accentuating their initial minor differences

Extinction of one species Resource partitioning: splitting the

niche Character displacement: two similar

species evolve in such a way as to become different from each other by accentuating their initial minor differences

Extinction of One SpeciesExtinction of One Species

Competition inNature

Competition inNature

Competition inNature

Competition inNature

Resource PartitioningResource Partitioning

Character Displacement

Character Displacement

Predator-Prey RelationshipsPredator-Prey Relationships

Possible OutcomesPossible Outcomes

offset oscillations in the population sizes of the predator and prey

evolution of prey adaptations that minimize predation

evolution of predator that enhance predator’s ability to obtain prey

coevolution of predator and prey

offset oscillations in the population sizes of the predator and prey

evolution of prey adaptations that minimize predation

evolution of predator that enhance predator’s ability to obtain prey

coevolution of predator and prey

Oscillations in Predator and Prey Populations

Oscillations in Predator and Prey Populations

SymbiosisSymbiosis Mutualism

Both the symbiont and host benefit (+/+)

Commensalism The symbiont benefits with little

effect on the host (+/0) Parasitism

The symbiont benefits to the detriment of the host (+/-)

Mutualism Both the symbiont and host

benefit (+/+) Commensalism

The symbiont benefits with little effect on the host (+/0)

Parasitism The symbiont benefits to the

detriment of the host (+/-)

Symbiotic RelationshipsSymbiotic Relationships

MutualismMutualism

coral and zooxanthellae

coral and zooxanthellae

ants and acacia trees

ants and acacia trees

Symbiotic RelationshipsSymbiotic Relationships

CommensalismCommensalism

cattle egrets and water buffalo

cattle egrets and water buffalo

Symbiotic RelationshipsSymbiotic Relationships

ParasitismParasitismendoparasitic

liver flukeendoparasitic

liver fluke

ectoparasitic monogenetic

fluke

ectoparasitic monogenetic

fluke

Species Diversity & Evenness

Species Diversity & Evenness

Keystone SpeciesKeystone Species A species whose presence in the

community exerts a significant influence on the structure of that community

A species whose presence in the community exerts a significant influence on the structure of that community

Keystone SpeciesKeystone Species

Trophic LevelsTrophic Levels 1st Trophic Level = Primary

Producers 2nd Trophic Level = Herbivores or

Primary Consumers 3rd Trophic Level and Higher =

Carnivores or Secondary (or higher) Consumers

Highest Trophic Level = Top Carnivore

Decomposers

1st Trophic Level = Primary Producers

2nd Trophic Level = Herbivores or Primary Consumers

3rd Trophic Level and Higher = Carnivores or Secondary (or higher) Consumers

Highest Trophic Level = Top Carnivore

Decomposers

Simple Food ChainsSimple Food Chains

primary producerprimary producer

primary consumerprimary consumer

secondary consumersecondary consumer

tertiary consumertertiary consumer

Food WebsFood Webs

Ecological SuccessionEcological Succession

The progressive change in the species composition of an

ecosystem.

The progressive change in the species composition of an

ecosystem.

New Bare SubstrateNew Bare Substrate

Colonizing StageColonizing Stage

Successionist StageSuccessionist Stage

Climax StageClimax Stage

Ecological SuccessionEcological Succession

Ecological SuccessionEcological Succession

Primary Versus Secondary Succession

Primary Versus Secondary Succession

No Disturbance (Competitive Exclusion Model)

Occasional Strong Disturbance (Intermediate Disturbance Model)

Constant Strong Disturbance (Colonial Model)

No Disturbance (Competitive Exclusion Model)

Occasional Strong Disturbance (Intermediate Disturbance Model)

Constant Strong Disturbance (Colonial Model)

Successional Models and their Impacts

Successional Models and their Impacts

Primary ProductionPrimary Production Primary production = the amount of

organic matter produced by autotrophs

Usually restricted to production by photoautotrophs (photosynthesis), but can also include production by chemoautotrophs (chemosynthesis)

We will restrict the discussion to primary production due to photosynthesis

Primary production = the amount of organic matter produced by autotrophs

Usually restricted to production by photoautotrophs (photosynthesis), but can also include production by chemoautotrophs (chemosynthesis)

We will restrict the discussion to primary production due to photosynthesis

Factors Influencing Primary Productivity

Factors Influencing Primary Productivity

LightLight intensitySpectral distribution

Temperature Evapotranspiration Inorganic nutrients

LightLight intensitySpectral distribution

Temperature Evapotranspiration Inorganic nutrients

Primary ProductionPrimary Production Gross primary production (GPP) =

the amount of light energy converted into chemical energy by photosynthesis

Respiration (R) = consumption of chemical energy by primary producers

Net primary production (NPP) = chemical energy stored in primary producers after respiration

Gross primary production (GPP) = the amount of light energy converted into chemical energy by photosynthesis

Respiration (R) = consumption of chemical energy by primary producers

Net primary production (NPP) = chemical energy stored in primary producers after respiration

% Earth’sSurface

Primary Productivity of Different Ecosystems

Primary Productivity of Different Ecosystems

NPP/m2/yr% Earth’sNPP

open oceanopen oceanreefs & algal bedsreefs & algal beds

tropical rain foresttropical rain forest

swamp & marshswamp & marsh

Energy Use by an HerbivoreEnergy Use by an Herbivore

fecesfeces

respirationrespiration

growthgrowth

plantsplants

herbivoresherbivorescarnivorescarnivores

decomposersdecomposers

Energy Flow Through Ecosystems

Energy Flow Through Ecosystems

Energy PyramidsEnergy Pyramids

Pyramid of NumbersPyramid of Numbers

Biomass PyramidsBiomass Pyramids

carbon dioxidecarbon dioxide

inorganic-Cinorganic-C

plantsplants

organic-Corganic-C

animalsanimals

organic-Corganic-C

decomposersdecomposers

organic-Corganic-C deathdeath

deat

hde

ath

eatingeating

photosynthesisphotosynthesis

respirationrespiration

respiration

respirationrespirationrespiration

The Carbon CycleThe Carbon Cycle

deathdeath

animalsanimals

organic-Norganic-N

decomposersdecomposers

organic-Norganic-N

eatingeating

nitratenitrate

inorganic-Ninorganic-N

plantsplants

organic-Norganic-Ninorganic nitrogen uptake

inorganic nitrogen uptake

ammoniaammoniainorganic-Ninorganic-N

nitrificationnitrification

The Nitrogen Cycle (Part I)The Nitrogen Cycle (Part I)

inorganic-Ninorganic-N

nitritenitrite

ammonificationammonification

nitratenitrate

inorganic-Ninorganic-N

N2N2

inorganic-Ninorganic-N

denitrificationdenitrification

ammoniaammoniainorganic-Ninorganic-N

nitrificationnitrification

The Nitrogen Cycle (Part II)The Nitrogen Cycle (Part II)

inorganic-Ninorganic-N

nitritenitrite

nitrogen fixationnitrogen fixation

GeneralizedBiogeochemical Cycles

GeneralizedBiogeochemical Cycles