Chapter 4Chapter 4Ecosystems and Living OrganismsEcosystems and Living Organisms

Overview Overview

o EvolutionEvolution• Natural SelectionNatural Selection• Domains and KingdomsDomains and Kingdoms

o Biological CommunitiesBiological Communities• Primary & Secondary SuccessionPrimary & Secondary Succession

o SymbiosisSymbiosis• Mutualism, Commensalism, ParasitismMutualism, Commensalism, Parasitism

o Predation & CompetitionPredation & Competitiono Resource PartitioningResource Partitioningo Keystone SpeciesKeystone Specieso Species Richness & Community StabilitySpecies Richness & Community Stability

EvolutionEvolution

o The cumulative genetic changes that The cumulative genetic changes that occur in a population of organisms over occur in a population of organisms over timetime• Current theories were proposed by Charles Current theories were proposed by Charles

Darwin, a 19Darwin, a 19thth century naturalist century naturalist• Evolution occurs through natural selectionEvolution occurs through natural selection

o Natural SelectionNatural Selection• Individuals with more favorable genetic traits Individuals with more favorable genetic traits

are more likely to survive and reproduceare more likely to survive and reproduce• Frequency of favorable traits increase in Frequency of favorable traits increase in

subsequent generationssubsequent generations

Natural SelectionNatural Selection

o Based on four observations about the Based on four observations about the natural worldnatural world

1.1. OverproductionOverproduction• Each species produces more offspring than will Each species produces more offspring than will

survive to maturitysurvive to maturity

2.2. VariationVariation• Individuals in a population exhibit variationIndividuals in a population exhibit variation

3.3. Limits on Population GrowthLimits on Population Growth• Resource limitations will keep population in Resource limitations will keep population in

checkcheck

4.4. Differential Reproductive SuccessDifferential Reproductive Success• Individuals with most favorable traits are more Individuals with most favorable traits are more

likely to reproducelikely to reproduce

Natural Natural SelectionSelection

o Darwin’s Darwin’s finches finches exemplified the exemplified the variation variation associated with associated with natural natural selectionselection

Domains and Kingdoms of LifeDomains and Kingdoms of Life

Biological CommunitiesBiological Communitieso Communities vary greatly in size and Communities vary greatly in size and

lack precise boundarieslack precise boundaries• They are often nestled within each otherThey are often nestled within each other

SuccessionSuccession

o The process where a community The process where a community develops slowly through a series of develops slowly through a series of speciesspecies

o Earlier species alter the environment in Earlier species alter the environment in some way to make it more habitable by some way to make it more habitable by other speciesother species• As more species arrive, the earlier species As more species arrive, the earlier species

are outcompeted and replacedare outcompeted and replaced

o Two types of successionTwo types of succession• Primary successionPrimary succession• Secondary successionSecondary succession

Primary SuccessionPrimary Succession

o Succession that begins in a previously Succession that begins in a previously uninhabited environmentuninhabited environment• No soil is present!No soil is present!• Ex: bare rocks, cooled lava fields, etc.Ex: bare rocks, cooled lava fields, etc.

o General Succession PatternGeneral Succession Pattern• Lichen secrete acids that crumble the rock Lichen secrete acids that crumble the rock

(soil begins to form)(soil begins to form)

Lichen mosses grasses shrubs Lichen mosses grasses shrubs forestsforests

o Primary Primary SuccessionSuccession

1.1. Bare rock with Bare rock with lichenlichen

2.2. Grasses and shrubsGrasses and shrubs

3.3. Forest communityForest community

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Secondary SuccessionSecondary Succession

o Succession that begins in an Succession that begins in an environment following destruction of all environment following destruction of all or part of the earlier communityor part of the earlier community• Ex: abandoned farmland, open area after Ex: abandoned farmland, open area after

firefire

o Does NOT follow primary succession!Does NOT follow primary succession!• Even though name may imply this Even though name may imply this

o Generally occurs more rapidly than Generally occurs more rapidly than primary successionprimary succession

Secondary Secondary Succession of an Succession of an abandoned farm field abandoned farm field in North Carolinain North Carolina

Interactions Among OrganismsInteractions Among Organisms

o SymbiosisSymbiosis• An intimate relationship between members An intimate relationship between members

of 2 or more speciesof 2 or more species• Participants may be benefited, harmed or Participants may be benefited, harmed or

unaffected by the relationshipunaffected by the relationship• Results of coevolutionResults of coevolution

o Three types of symbiosisThree types of symbiosis• MutualismMutualism• CommensalismCommensalism• ParasitismParasitism

MutualismMutualismo Symbiotic relationship in which both Symbiotic relationship in which both

members benefitmembers benefito Ex: Mycorrihzal fungi and plant rootsEx: Mycorrihzal fungi and plant roots

• Fungus grows around and into roots Fungus grows around and into roots providing roots with otherwise unavailable providing roots with otherwise unavailable nitrogen from soilnitrogen from soil

• Roots provide fungi with food produced by Roots provide fungi with food produced by photosynthesis in the plantphotosynthesis in the plant

•Left: root growth Left: root growth without fungiwithout fungi

•Right: root Right: root growth with fungigrowth with fungi

CommensalismCommensalismo Symbiotic relationship where one species Symbiotic relationship where one species

benefits and the other is neither harmed nor benefits and the other is neither harmed nor helpedhelped

o Ex: epiphytes and tropical treesEx: epiphytes and tropical trees• Epiphyte anchors Epiphyte anchors

itself to the tree, itself to the tree, but does not take but does not take nutrients from nutrients from the treethe tree

• Epiphyte benefits Epiphyte benefits from getting from getting closer to sunlight, closer to sunlight, tropical tree is tropical tree is not affectednot affected

ParasitismParasitism

o Symbiotic relationship in which one Symbiotic relationship in which one species is benefited and the other is species is benefited and the other is harmedharmed• Parasites rarely kill their hostsParasites rarely kill their hostso Ex: Varroa mites Ex: Varroa mites and honeybeesand honeybees• Mites live in the Mites live in the

breathing tubes breathing tubes of the bees, of the bees, sucking their sucking their blood and blood and weakening themweakening them

PredationPredation

o The consumption of one species by The consumption of one species by anotheranother

o Many predator-prey interactionsMany predator-prey interactions• Most common is pursuit and ambushMost common is pursuit and ambush

o Plants and animals have established Plants and animals have established specific defenses against predation specific defenses against predation through evolutionthrough evolution

Pursuit and AmbushPursuit and Ambush

o Pursuing prey simply means chasing it Pursuing prey simply means chasing it down and catching itdown and catching it• Ex: Day gecko and spider (see picture)Ex: Day gecko and spider (see picture)

o Ambush is when predators catch prey Ambush is when predators catch prey unawareunaware• CamouflageCamouflage• Attract prey with Attract prey with

colors or lightcolors or light

Plant Defenses Against Plant Defenses Against PredationPredation

o Plants cannot flee predatorsPlants cannot flee predatorso AdaptationsAdaptations

• Spikes, thorns, leathery leaves, thick waxSpikes, thorns, leathery leaves, thick wax• Protective chemicals that are poisonous or Protective chemicals that are poisonous or

unpalatableunpalatable

Animal Defenses Against Animal Defenses Against PredationPredation

o Fleeing or runningFleeing or runningo Mechanical defensesMechanical defenses

• Ex: quills of porcupines, shell of turtlesEx: quills of porcupines, shell of turtleso Living in groupsLiving in groupso CamouflageCamouflageo Chemical defenses- Chemical defenses- poisonspoisons

• Ex: brightly colored poison Ex: brightly colored poison arrow frogarrow frog

CompetitionCompetition

o Interaction among organisms that vie Interaction among organisms that vie for the same resource in an ecosystemfor the same resource in an ecosystem

o IntraspecificIntraspecific• Competition between individuals in a Competition between individuals in a

populationpopulation

o Interspecific Interspecific • Competition between individuals in 2 Competition between individuals in 2

different speciesdifferent species

Ecological NicheEcological Niche

o The totality of an organisms The totality of an organisms adaptations, its use of resources, and adaptations, its use of resources, and the lifestyle to which it is fittedthe lifestyle to which it is fitted

o Takes into account all aspect of an Takes into account all aspect of an organisms existenceorganisms existence• Physical, chemical, biological factors Physical, chemical, biological factors

needed to surviveneeded to survive• HabitatHabitat• Abiotic components of the environmentAbiotic components of the environment

• Ex: Light, temperature, moistureEx: Light, temperature, moisture

Ecological NicheEcological Nicheo Fundamental nicheFundamental niche

• Potential idealized ecological niche Potential idealized ecological niche

o Realized nicheRealized niche• The actual niche the organism occupiesThe actual niche the organism occupies

o Ex: Green Anole and Brown AnoleEx: Green Anole and Brown Anole

Ecological NicheEcological Niche

o Green Anole and Brown AnoleGreen Anole and Brown Anole• Fundamental niches of 2 lizards initially Fundamental niches of 2 lizards initially

overlappedoverlapped• Brown anole eventually out-competed the Brown anole eventually out-competed the

green anole- reduced the green anole’s green anole- reduced the green anole’s realized nicherealized niche

Limiting Resources (factors)Limiting Resources (factors)

o Any environmental resource that, because it is Any environmental resource that, because it is scarce or at unfavorable levels, restricts the scarce or at unfavorable levels, restricts the ecological niche of an organismecological niche of an organism

Interspecific: Competition using Interspecific: Competition using ParameciumParamecium

Competitive Exclusion & Resource Competitive Exclusion & Resource PetitioningPetitioning

o Competitive ExclusionCompetitive Exclusion• One species excludes another from a portion of the One species excludes another from a portion of the

same niche as a result of competition for resourcessame niche as a result of competition for resources

o Resource PartitioningResource Partitioning• Coexisting species’ niche differ from each other in Coexisting species’ niche differ from each other in

some waysome way

Keystone SpeciesKeystone Species

o A species that exerts profound A species that exerts profound influence on a communityinfluence on a community• More important to the community than More important to the community than

what would be expected based on what would be expected based on abundanceabundance

o The dependence of other species on the The dependence of other species on the keystone species is apparent when the keystone species is apparent when the keystone species is removedkeystone species is removed• Protecting keystone species is a goal to Protecting keystone species is a goal to

conservation biologistsconservation biologists

Species RichnessSpecies Richness

o The number of The number of species in a species in a communitycommunity• Tropical Tropical

rainforests = high rainforests = high species richnessspecies richness

• Isolated island = Isolated island = low species low species richnessrichness

o Related to the Related to the abundance of abundance of potential potential ecological nichesecological niches