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Wolves of YellowstoneWolves of Yellowstone StonefliesStoneflies Invasive speciesInvasive species Wildlife corridorsWildlife corridors Flying foxesFlying foxes Dung beetlesDung beetles Sea OttersSea Otters Sea lampreySea lamprey Ants and acacia treeAnts and acacia tree

Community EcologyCommunity Ecology

AP Environmental AP Environmental ScienceScience

Milton High SchoolMilton High School

Habitat fragmentation causes Habitat fragmentation causes significant decline in species significant decline in species diversitydiversity Reduce species richnessReduce species richness Reduce amount of functional habitatReduce amount of functional habitat Cause isolation of a speciesCause isolation of a species Possibility of genetic drift or inbreedingPossibility of genetic drift or inbreeding

Edge Effects Associated Edge Effects Associated with Habitat Fragmentation with Habitat Fragmentation Can Reduce BiodiversityCan Reduce Biodiversity Makes many species vulnerable Makes many species vulnerable

to stresses such as predators and to stresses such as predators and firesfires

Creates barriers that can prevent Creates barriers that can prevent some species from colonizing new some species from colonizing new areas and finding food and matesareas and finding food and mates

Edge effect

Conservation Conservation Biologists Protect Biologists Protect BiodiversityBiodiversity Preserving large areas of habitatPreserving large areas of habitat Using migration corridors to link Using migration corridors to link

smaller habitat patchessmaller habitat patches

Tunnels under roads

Bridges over roads

Who benefits from wildlife corridors?

Species diversitySpecies diversity

Species richness Species richness – – number of different number of different speciesspecies

Species evenness Species evenness – – abundance of abundance of individuals within individuals within each of those specieseach of those species

The Most Species-rich The Most Species-rich EnvironmentsEnvironments Tropical forestsTropical forests Coral reefsCoral reefs Deep seaDeep sea Large tropical lakesLarge tropical lakes

Three Major Factors Three Major Factors Affect Species Affect Species DiversityDiversity Latitude (distance from equator)Latitude (distance from equator) Depth (aquatic systems)Depth (aquatic systems) Pollution (aquatic systems)Pollution (aquatic systems)

Number of Species Found Number of Species Found on an Island Determined by on an Island Determined by a Balance Between:a Balance Between: Rate at which Rate at which

new species new species immigrate to immigrate to the islandthe island

The rate at The rate at which species which species become extinct become extinct on the islandon the island

Two features of an island Two features of an island which affects its which affects its immigration and extinction immigration and extinction raterate Island’s sizeIsland’s size

Island’s Island’s distance distance from the from the mainlandmainland

Canary Archipelago

What can you predict about how each island was

colonized by wild species?

1) The closer the island is to another land mass, the higher the probability of colonization.

2) The older the island, the more likely it will be colonized.

3) The larger the island, the more species are likely to be established.

4) The geographic isolation reduces gene flow between populations.

5) Over time, colonial populations become genetically divergent from their parent population due to natural selection, mutation, and/or genetic drift

General principles of General principles of island colonizationisland colonization

Explain Robert MacArthur and E.O. Wilson’s Theory of

Island Biogeography? How is this theory

applied to the management of National Parks?

Island Biogeography

Critical Roles of Critical Roles of Keystone SpeciesKeystone Species Pollination of flowering plant speciesPollination of flowering plant species Dispersion of seeds by fruit-eating Dispersion of seeds by fruit-eating

animalsanimals Habitat modification (Gopher tortoise)Habitat modification (Gopher tortoise) Predation by top carnivores to control Predation by top carnivores to control

populations of various speciespopulations of various species Improving the ability of plant species to Improving the ability of plant species to

obtain soil minerals and waterobtain soil minerals and water Efficient recycling of animal wastesEfficient recycling of animal wastes

Sea Otter: Sea Otter: A keystone speciesA keystone species

Sea otters feed on the sea urchin which eats the base of the kelp plants (killing the

kelp plants)

The Dodo bird inhabited the island of Mauritius in the Indian

Ocean

In 1505, the Portuguese became the 1st humans to set foot on

Mauritius Dodo bird source of food for the sailors

Dutch used the island as a penal colony and brought pigs and monkeys which ate the eggs of the dodo bird

A combination of human exploitation and introduced species

significantly reduced the dodo population

The last dodo bird

was killed in 1681

Scientists discovered a certain species of tree was becoming quite rare on Mauritius. All of

the remaining trees of their species were about 300 years old and no new trees had germinated since the late 1600’s.

Was it coincidence that the tree had stopped reproducing 300 years ago and that the dodo bird had become extinct

300 years ago?

The dodo ate the fruit of the tree and the seed only became active and could grow

after passing through the digestive tract of the dodo bird.

Scientists discovered the

turkey’s digestive tract accomplishes the same task and they are

now using turkeys to

begin a new generation of

the tree - Tambalacoque

Biological indicator species are Biological indicator species are unique environmental indicators as unique environmental indicators as they offer a signal of the biological they offer a signal of the biological

condition of a particular habitatcondition of a particular habitat

Using bioindicators as an early warning of pollution or

degradation in an ecosystem can

help sustain critical resources

Fish are an excellent Fish are an excellent indicator of watershed indicator of watershed

health because:health because: Live in water all of their Live in water all of their

lifelife Differ in their tolerance Differ in their tolerance

levels to amount and levels to amount and types of pollutiontypes of pollution

Are easy to collectAre easy to collect Live for several yearsLive for several years Are easy to identifyAre easy to identify

Benthic macroinvertebrates Benthic macroinvertebrates are good indicators are good indicators

because:because: Live in water for all or most of their Live in water for all or most of their

lifelife Stay in areas suitable for their Stay in areas suitable for their

survival survival Are easy to collectAre easy to collect Differ in their tolerance to amount Differ in their tolerance to amount

and types of pollutionand types of pollution Are easy to identifyAre easy to identify Often live for more than one yearOften live for more than one year Have limited mobilityHave limited mobility Are integrators of environmental Are integrators of environmental

conditioncondition

Possible Causes of Possible Causes of Amphibian DeclinesAmphibian Declines Loss of habitatLoss of habitat Prolonged droughtProlonged drought Pollution (pesticides, nitrates, pH)Pollution (pesticides, nitrates, pH) Increases in ultraviolet radiationIncreases in ultraviolet radiation Increase parasitismIncrease parasitism OverhuntingOverhunting Epidemic diseasesEpidemic diseases Immigration or introduction of alien Immigration or introduction of alien

predators and competitorspredators and competitors

What is the disadvantage?

Five Basic Types of Five Basic Types of Interactions Between Interactions Between SpeciesSpecies Interspecific competitionInterspecific competition Intraspecific competitionIntraspecific competition PredationPredation ParasitismParasitism MutualismMutualism commensalismcommensalism

Commensalism

Remora

“sucking” disc does not harm shark

Bacteria in your intestines

Significant Niche Overlap – Significant Niche Overlap – one of the competing one of the competing species mustspecies must Migrate to another areaMigrate to another area Shift its feeding habits or Shift its feeding habits or

behavior through natural behavior through natural selection or evolutionselection or evolution

Suffer a sharp population declineSuffer a sharp population decline Become extinct in that areaBecome extinct in that area

How Species Avoid How Species Avoid PredatorsPredators

Run, swim, fly fastRun, swim, fly fast Highly developed Highly developed

sense of smell or sense of smell or sightsight

Protective shellsProtective shells Thick barkThick bark SpinesSpines camouflagecamouflage

Parts that break offParts that break off Chemical warfareChemical warfare Warning colorationWarning coloration Behavioral Behavioral

strategiesstrategies– Puffing upPuffing up– MimicryMimicry– SchoolingSchooling– Living in large groupsLiving in large groups– Spreading their wingsSpreading their wings

Avoiding predators

Examples of Primary Examples of Primary SuccessionSuccession Bare rock exposed by glacial Bare rock exposed by glacial

retreat or severe soil erosionretreat or severe soil erosion Newly cooled lavaNewly cooled lava An abandoned highway or parking An abandoned highway or parking

lotlot Newly created shallow pond or Newly created shallow pond or

reservoirreservoir

Pioneer species start Pioneer species start soil formation process soil formation process by:by: Trapping wind-blown soil particles and tiny Trapping wind-blown soil particles and tiny

pieces of detrituspieces of detritus Producing tiny bits of organic matterProducing tiny bits of organic matter Secreting mild acids that slowly fragment Secreting mild acids that slowly fragment

and break down the rockand break down the rock

Lichen

Examples of Secondary Examples of Secondary SuccessionSuccession Abandoned farmlandsAbandoned farmlands Burned or cut forestsBurned or cut forests Heavily polluted streamsHeavily polluted streams Land that has been dammed or Land that has been dammed or

floodedflooded

Three Aspects of Three Aspects of StabilityStability Persistence – resist disturbancePersistence – resist disturbance

Constancy – keep within limitsConstancy – keep within limits

Resilience – bounce backResilience – bounce back

The End

Role of positive and negative Role of positive and negative feedback loops in the stability of an feedback loops in the stability of an ecosystemecosystem

Negative feedback loops promote Negative feedback loops promote stability in a dynamic systemstability in a dynamic system

Positive feedback loops usually leads Positive feedback loops usually leads to one or more populations being to one or more populations being wiped out (local extinction)wiped out (local extinction)

Positive feedback loop = causes a system to change further in the same direction (positive refers to the direction of change, rather than desirability of the outcome)

Negative feedback loop = causes a system to change in the opposite direction

Positive feedback loopPositive feedback loop

A warmer atmosphere will melt ice and this

changes the Earth’s albedo which

further warms the atmosphere

An increase in temperature will melt the permafrost in the tundra causing a release of trapped carbon dioxide and methane (both are greenhouse

gases)

Negative feedback Negative feedback looploop

Predator-prey relationship

The moose population will rise and fall in

response to the wolf population

Positive and negative feedback loops coupled together

1. The settlers of Easter Island found plenty of natural resources2. The Islanders had many children and the population went up3. The island’s tree and soil resources were used faster than they could be

renewed4. Without trees Islanders could not build traditional seagoing canoes5. All of the island’s natural resources were used up6. Both the population and the civilization collapsed

Example of negative Example of negative feedback loopfeedback loop

An example of negative feedback is body temperature regulation. If blood temperature rises too high, this is sensed by specialized neurons in the hypothalamus of the brain. They signal other nerve centers, which in turn send signals to the blood vessels of the skin. As these blood vessels dilate, more blood flows close to the body surface and excess heat radiates from the body. If this is not enough to cool the body back to its set point, the brain activates sweating. Evaporation of sweat from the skin has a strong cooling effect, as we feel when we are sweaty and stand in front of a fan.

Read more: Homeostasis - Biology Encyclopedia - cells, body, examples, function, human, process, system, organisms, blood http://www.biologyreference.com/Ho-La/Homeostasis.html#ixzz11mSI4EzD

Example of positive Example of positive feedback loopfeedback loop

An example of its beneficial effect is seen in blood clotting. Part of the complex biochemical pathway of clotting is the production of an enzyme that forms the matrix of the blood clot, but also speeds up the production of still more thrombin. That is, it has a self- catalytic , self-accelerating effect, so that once the clotting process begins, it runs faster and faster until, ideally, bleeding stops. Thus, this positive feedback loop is part of a larger negative feedback loop, one that is activated by bleeding and ultimately works to stop the bleeding.

Read more: Homeostasis - Biology Encyclopedia - cells, body, examples, function, human, process, system, organisms, blood http://www.biologyreference.com/Ho-La/Homeostasis.html#ixzz11mSpKQyy