Chapter 4Chapter 4Ecosystems and Living Ecosystems and Living OrganismsOrganisms

Overview of Chapter 4Overview of Chapter 4

EvolutionEvolution Natural SelectionNatural Selection

Biological CommunitiesBiological Communities SymbiosisSymbiosis Predation & CompetitionPredation & Competition

Species Richness & Community Species Richness & Community StabilityStability

Community DevelopmentCommunity Development SuccessionSuccession

EvolutionEvolution

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 proposed by Charles Current theories proposed by Charles

Darwin, a 19Darwin, a 19thth century naturalist century naturalist Occurs through natural selectionOccurs through natural selection

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

Based on four observations about Based on four observations about the natural world:the natural world:

1.1. High Reproductive CapacityHigh Reproductive Capacity2.2. Heritable VariationHeritable Variation3.3. Limits on Population Growth, or a Limits on Population Growth, or a

Struggle For ExistenceStruggle For Existence4.4. Differential Reproductive SuccessDifferential Reproductive Success

Natural Natural SelectionSelection

DarwinDarwin’’s s finches finches exemplified exemplified the variation the variation associated associated with natural with natural selectionselection

The Modern SynthesisThe Modern Synthesis

An attempt to An attempt to explain variation explain variation among offspring among offspring (mutation)(mutation) Includes Includes

knowledge from knowledge from genetics, genetics, classification, classification, developmental developmental biology, fossils and biology, fossils and ecology ecology

Domains of LifeDomains of Life

Biological CommunitiesBiological Communities 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

Community Interaction in Oak Community Interaction in Oak ForestForest

Oak Forest Oak Forest Community Community RelationshipsRelationships Possible to link Possible to link

lyme disease to lyme disease to bumper acorn bumper acorn cropscrops

Ecological NicheEcological Niche

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

Takes into account all aspects of an Takes into account all aspects 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

Ecological NicheEcological Niche

Fundamental nicheFundamental niche Potential idealized ecological niche Potential idealized ecological niche

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

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

Ecological NicheEcological Niche

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 Brown anole eventually out-competed

the green anole, thereby reducing the the green anole, thereby reducing the green anolegreen anole’’s realized niches realized niche

Limiting ResourcesLimiting Resources

Any environmental resource that restricts the Any environmental resource that restricts the ecological niche of an organism because it is ecological niche of an organism because it is scarce or at an unfavorable levelscarce or at an unfavorable level

CompetitionCompetition

Interaction among organisms that vie Interaction among organisms that vie for the same resource in an for the same resource in an ecosystemecosystem

IntraspecificIntraspecific Competition between individuals in a Competition between individuals in a

populationpopulation Interspecific Interspecific

Competition between individuals in 2 Competition between individuals in 2 different speciesdifferent species

Interspecific CompetitionInterspecific Competition

Competitive Exclusion & Resource Competitive Exclusion & Resource PartitioningPartitioning

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 Resource Partitioning (below)Resource Partitioning (below)

Coexisting species share a niche by using it in Coexisting species share a niche by using it in different ways different waysdifferent ways different ways

SymbiosisSymbiosis

An intimate relationship between An intimate relationship between members of 2 or more speciesmembers of 2 or more species Participants may be benefited, harmed Participants may be benefited, harmed

or unaffected by the relationshipor unaffected by the relationship Result of coevolutionResult of coevolution

Three types of symbiosisThree types of symbiosis MutualismMutualism CommensalismCommensalism ParasitismParasitism

MutualismMutualism Symbiotic relationship in which both Symbiotic relationship in which both

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

Fungus provides roots with unavailable Fungus provides roots with unavailable nitrogen from soilnitrogen from soil

Roots provide fungi with energy Roots provide fungi with energy produced by photosynthesis in the plantproduced by photosynthesis in the plant

Left: root growth Left: root growth without fungiwithout fungi

Right: root Right: root growth with fungigrowth with fungi

CommensalismCommensalism 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

Ex: epiphytes and tropical treesEx: epiphytes and tropical trees

Epiphytes use Epiphytes use trees as anchortrees as anchor

Epiphytes Epiphytes benefit from benefit from getting closer to getting closer to sunlight, sunlight, tropical tree is tropical tree is not affectednot affected

ParasitismParasitism 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 hosts

Ex: ticksEx: ticks Ticks attach Ticks attach

themselves to themselves to skin of animals skin of animals and consume and consume their bloodtheir blood

PredationPredation

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

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

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

Pursuing prey- chasing prey down Pursuing prey- chasing prey down and catching itand catching it Ex: Day gecko and spider (below)Ex: Day gecko and spider (below)

Ambush- predators catch prey Ambush- predators catch prey unawareunaware CamouflageCamouflage Attract prey with Attract prey with

colors or lightcolors or light

Plant Defenses Against Plant Defenses Against HerbivoresHerbivores

Plants cannot flee predatorsPlants cannot flee predators AdaptationsAdaptations

Spikes, thorns, leathery leaves, thick Spikes, thorns, leathery leaves, thick waxwax

Protective chemicals that are poisonous Protective chemicals that are poisonous or unpalatableor unpalatable

Defensive Adaptation of Defensive Adaptation of AnimalsAnimals Fleeing or runningFleeing or running Mechanical defensesMechanical defenses

Ex: quills of porcupines, shell of turtlesEx: quills of porcupines, shell of turtles Living in groupsLiving in groups CamouflageCamouflage Chemical defenses - Chemical defenses - poisonspoisons

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

Keystone SpeciesKeystone Species

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

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

conservation biologistsconservation biologists

Species RichnessSpecies Richness

The number of The number of species in a species in a communitycommunity Tropical rainforests Tropical rainforests

= high species = high species richnessrichness

Isolated island = Isolated island = low species richnesslow species richness

Related to the Related to the abundance of abundance of potential ecological potential ecological nichesniches

Invasive Species DestroyInvasive Species Destroy Species Richness Species Richness

Asian Tiger ShrimpAsian Tiger Shrimp

Ecosystem ServicesEcosystem Services

Important environmental benefits Important environmental benefits that ecosystems provide, such as:that ecosystems provide, such as: Clean air to breatheClean air to breathe Clean water to drinkClean water to drink Fertile soil in which to grow crops Fertile soil in which to grow crops A forest to go camping inA forest to go camping in

Community DevelopmentCommunity Development

Succession: the process where a Succession: the process where a community develops slowly through a community develops slowly through a series of speciesseries of species Earlier species alter the environment in some Earlier species alter the environment in some

way to make it more habitable by other way to make it more habitable by other speciesspecies

As more species arrive, the earlier species As more species arrive, the earlier species are outcompeted and replacedare outcompeted and replaced

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

Primary SuccessionPrimary Succession

Succession that begins in a Succession that begins in a previously uninhabited environmentpreviously uninhabited environment No soil is presentNo soil is present Ex: bare rocks, cooled lava fields, etc.Ex: bare rocks, cooled lava fields, etc.

General Succession PatternGeneral Succession Pattern Lichen secrete acids that crumble the Lichen secrete acids that crumble the

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

Lichen mosses grasses shrubs Lichen mosses grasses shrubs forestsforests

Primary SuccessionPrimary Succession1.1. Bare rock with Bare rock with

lichenlichen

2.2. Grasses and shrubsGrasses and shrubs

3.3. FoForest communityrest community

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Secondary SuccessionSecondary Succession

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

after fireafter fire

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