chapter 8 community ecology. core case study: why should we care about the american alligator? ...

Chapter 8Chapter 8

Community EcologyCommunity Ecology

Core Case Study:Core Case Study:Why Should We Care about the Why Should We Care about the

American Alligator?American Alligator?

Hunters wiped out Hunters wiped out population to the population to the point of near point of near extinction.extinction.

Alligators have Alligators have important ecological important ecological role.role.

Figure 7-1Figure 7-1

Core Case Study:Core Case Study:Why Should We Care about the Why Should We Care about the

American Alligator?American Alligator? Dig deep depressions (gator holes).Dig deep depressions (gator holes).

Hold water during dry spells, serve as refuges Hold water during dry spells, serve as refuges for aquatic life.for aquatic life.

Build nesting mounds.Build nesting mounds. provide nesting and feeding sites for birds.provide nesting and feeding sites for birds. Keeps areas of open water free of vegetation.Keeps areas of open water free of vegetation.

Alligators are a keystone species:Alligators are a keystone species: Help maintain the structure and function of the Help maintain the structure and function of the

communities where it is found.communities where it is found.

Biological communities differ in the types and Biological communities differ in the types and numbers of species they contain and the numbers of species they contain and the ecological roles those species play. ecological roles those species play. Species diversitySpecies diversity= = species richnessspecies richness: :

the number of different species it containsthe number of different species it contains species evennessspecies evenness:: combined with the abundance of individuals combined with the abundance of individuals

within each of those specieswithin each of those species

Species Diversity and Niche StructureSpecies Diversity and Niche Structure

Niche structure: how many potential Niche structure: how many potential ecological niches occur, how they resemble ecological niches occur, how they resemble or differ, and how the species occupying or differ, and how the species occupying different niches interact.different niches interact.

Geographic location: species diversity is Geographic location: species diversity is highest in the tropics and declines as we highest in the tropics and declines as we move from the equator toward the poles.move from the equator toward the poles.

TYPES OF SPECIESTYPES OF SPECIES

Native, nonnative, indicator, keystone, and Native, nonnative, indicator, keystone, and foundation species play different ecological foundation species play different ecological roles in communities.roles in communities.

Case Study:Case Study:Species Diversity on IslandsSpecies Diversity on Islands

MacArthur and Wilson proposed the species MacArthur and Wilson proposed the species equilibrium model or theory of island equilibrium model or theory of island biogeography in the 1960’s.biogeography in the 1960’s.

Model projects that at some point the rates of Model projects that at some point the rates of immigration and extinction should reach an immigration and extinction should reach an equilibrium based on:equilibrium based on:

Island size & Distance to nearest mainlandIsland size & Distance to nearest mainland

SPECIES INTERACTIONS: SPECIES INTERACTIONS: COMPETITION AND PREDATIONCOMPETITION AND PREDATION

Species can interact through competition, Species can interact through competition, predation, parasitism, mutualism, and predation, parasitism, mutualism, and commensalism.commensalism.

Some species evolve adaptations that Some species evolve adaptations that allow them to reduce or avoid competition allow them to reduce or avoid competition for resources with other species (resource for resources with other species (resource partitioning).partitioning).

Why do species compete?Why do species compete?

If two different species compete it is called If two different species compete it is called _______ competition._______ competition.

Interspecific Interspecific If two of the same species compete it is called If two of the same species compete it is called _______ competition._______ competition.

Intraspecific Intraspecific If competition is intense, what must the less If competition is intense, what must the less competitive species do?competitive species do?

What is resource partitioning?What is resource partitioning?

Resource PartitioningResource Partitioning

Each species minimizes Each species minimizes competition with the others competition with the others for food by spending at for food by spending at least half its feeding time least half its feeding time in a distinct portion of the in a distinct portion of the spruce tree and by spruce tree and by consuming somewhat consuming somewhat different insect species.different insect species.


PREDATIONPREDATION

Some prey escape Some prey escape their predators or their predators or have outer have outer protection, some protection, some are camouflaged, are camouflaged, and some use and some use chemicals to repel chemicals to repel predators.predators.


SPECIES INTERACTIONS: SPECIES INTERACTIONS: PARASITISM, MUTUALISM, AND PARASITISM, MUTUALISM, AND

COMMENSALIMCOMMENSALIM

Parasitism occurs when one species feeds Parasitism occurs when one species feeds on part of another organism. +, -on part of another organism. +, -

In mutualism, two species interact in a way In mutualism, two species interact in a way that benefits both. +, +that benefits both. +, +

Commensalism is an interaction that benefits Commensalism is an interaction that benefits one species but has little, if any, effect on the one species but has little, if any, effect on the other species. +, 0other species. +, 0

Parasites: Sponging Off of OthersParasites: Sponging Off of Others

Although parasites can harm their hosts, they Although parasites can harm their hosts, they can promote community biodiversity.can promote community biodiversity. Some parasites live in host (micororganisms, Some parasites live in host (micororganisms,

tapeworms).tapeworms). Some parasites live outside host (fleas, ticks, Some parasites live outside host (fleas, ticks,

mistletoe plants, sea lampreys).mistletoe plants, sea lampreys). Some have little contact with host (dump-nesting Some have little contact with host (dump-nesting

birds like cowbirds, some duck species)birds like cowbirds, some duck species)

Mutualism: Win-Win RelationshipMutualism: Win-Win Relationship

Two species Two species can interact in can interact in ways that ways that benefit both of benefit both of them.them.


Commensalism: Using without HarmingCommensalism: Using without Harming

Some species Some species interact in a way interact in a way that helps one that helps one species but has species but has little or no effect little or no effect on the other.on the other.


Indicator Species: Indicator Species: Biological Smoke AlarmsBiological Smoke Alarms

Species that serve as early warnings of Species that serve as early warnings of damage to a community or an ecosystem.damage to a community or an ecosystem. Presence or absence of trout species because Presence or absence of trout species because

they are sensitive to temperature and oxygen they are sensitive to temperature and oxygen levels. levels.

Are often amphibians, Why?Are often amphibians, Why?

Case Study: Case Study: Why are Amphibians Vanishing?Why are Amphibians Vanishing?

Frogs serve as indicator species because Frogs serve as indicator species because different parts of their life cycles can be easily different parts of their life cycles can be easily disturbed.disturbed. Figure 7-3Figure 7-3

Case Study: Case Study: Why are Amphibians Vanishing?Why are Amphibians Vanishing?

Habitat loss and fragmentation.Habitat loss and fragmentation. Prolonged drought.Prolonged drought. Pollution.Pollution. Increases in ultraviolet radiation.Increases in ultraviolet radiation. Parasites.Parasites. Viral and Fungal diseases.Viral and Fungal diseases. Overhunting.Overhunting. Natural immigration or deliberate introduction Natural immigration or deliberate introduction

of nonnative predators and competitors.of nonnative predators and competitors.

What does richness refer to?What does richness refer to?

A.A. The number of individuals of each speciesThe number of individuals of each species

B.B. The number of different speciesThe number of different species

C.C. The number of edge effectsThe number of edge effects

D.D. The number of ecotonesThe number of ecotones

E.E. The number of different communitiesThe number of different communities

Prey are least likely to defend themselves Prey are least likely to defend themselves against predators byagainst predators by

A. camouflageA. camouflage

B. acute senses of sight and smellB. acute senses of sight and smell

C. protective shellsC. protective shells

D. pursuit and ambushD. pursuit and ambush

E. warning and ambushE. warning and ambush

Interspecific competition can be avoided byInterspecific competition can be avoided by

A.A. Eating at different timesEating at different times

B.B. Resource partitioningResource partitioning

C.C. Character displacementCharacter displacement

D.D. All of the aboveAll of the above

E.E. None of these answersNone of these answers

All of the following are ectoparasites exceptAll of the following are ectoparasites except

A.A. Fleas and ticksFleas and ticks

B.B. MosquitoesMosquitoes

C.C. MistletoeMistletoe

D.D. TapewormsTapeworms

E.E. Athletes footAthletes foot

Species whose roles in an ecosystem are Species whose roles in an ecosystem are much more important than their abundance much more important than their abundance would suggest, are calledwould suggest, are called

A.A. Nonnative speciesNonnative species

B.B. Native speciesNative species

C.C. Keystone speciesKeystone species

D.D. Specialist speciesSpecialist species

E.E. Generalist speciesGeneralist species

Keystone Species: Major PlayersKeystone Species: Major Players

Keystone species help determine the types Keystone species help determine the types and numbers of other species in a and numbers of other species in a community thereby helping to sustain it.community thereby helping to sustain it.

Figures 7-4 and 7-5Figures 7-4 and 7-5

Foundation Species: Foundation Species: Other Major PlayersOther Major Players

Expansion of keystone species category.Expansion of keystone species category. Foundation species can create and enhance Foundation species can create and enhance

habitats that can benefit other species in a habitats that can benefit other species in a community.community. Elephants push over, break, or uproot trees, Elephants push over, break, or uproot trees,

creating forest openings promoting grass growth creating forest openings promoting grass growth for other species to utilize.for other species to utilize.

ECOLOGICAL STABILITY AND ECOLOGICAL STABILITY AND SUSTAINABILITYSUSTAINABILITY

Many species play a role in ecosystemsMany species play a role in ecosystems Can keystone species be top predators?Can keystone species be top predators? Can they be decomposers?Can they be decomposers?

How Would You Vote?How Would You Vote?

Do we have an ethical obligation to protect Do we have an ethical obligation to protect shark species from premature extinction and shark species from premature extinction and treat them humanely?treat them humanely? No. It's impractical to force international laws on No. It's impractical to force international laws on

individual fishermen that are simply trying to feed individual fishermen that are simply trying to feed their families with the fishing techniques that they their families with the fishing techniques that they have.have.

Yes. Sharks are an important part of marine Yes. Sharks are an important part of marine ecosystems. They must be protected and, like all ecosystems. They must be protected and, like all animals, they should be humanely treated. animals, they should be humanely treated.

COMMUNITY STRUCTURE AND COMMUNITY STRUCTURE AND SPECIES DIVERSITYSPECIES DIVERSITY

Biological communities differ in their structure Biological communities differ in their structure and physical appearance.and physical appearance.


ECOLOGICAL SUCCESSION: ECOLOGICAL SUCCESSION: COMMUNITIES IN TRANSITIONCOMMUNITIES IN TRANSITION

New environmental conditions allow one New environmental conditions allow one group of species in a community to replace group of species in a community to replace other groups.other groups.

Ecological successionEcological succession: the gradual change : the gradual change in species composition of a given areain species composition of a given area Primary successionPrimary succession: the gradual establishment : the gradual establishment

of biotic communities in lifeless areas where of biotic communities in lifeless areas where there is no soil or sediment.there is no soil or sediment.

Secondary successionSecondary succession: series of communities : series of communities develop in places containing soil or sediment.develop in places containing soil or sediment.

Primary succession begins with an essentially Primary succession begins with an essentially lifeless are where there is no soil in a terrestrial lifeless are where there is no soil in a terrestrial

ecosystemecosystem

What are the steps What are the steps involved?involved?

1)Pioneer species1)Pioneer species

2)Early successional 2)Early successional plantsplants

3)Mid-successional 3)Mid-successional plantsplants

4)Late successional 4)Late successional plantplant


Secondary succession begins in an area where Secondary succession begins in an area where the natural community has been disturbed.the natural community has been disturbed.

What 3 factors What 3 factors control the rate at control the rate at which ecological which ecological succession takes succession takes place?place?

1)Facilitation1)Facilitation

2)Inhibition2)Inhibition

3)Tolerance3)Tolerance


What are the 3 aspects of stability or What are the 3 aspects of stability or sustainability in living systems?sustainability in living systems?

A system that resists being disturbed or altered A system that resists being disturbed or altered is said to have _____or _____.is said to have _____or _____.

Inertia or persistenceInertia or persistenceA population that can keep its numbers within A population that can keep its numbers within

limits imposed by resources shows _____.limits imposed by resources shows _____.ConstancyConstancyA system that is able to repair damage after a A system that is able to repair damage after a

moderate external disturbance shows moderate external disturbance shows ______.______.

ResilienceResilience

ECOLOGICAL STABILITY AND ECOLOGICAL STABILITY AND SUSTAINABILITYSUSTAINABILITY

Having many different species appears to Having many different species appears to increase the sustainability of many increase the sustainability of many communities.communities.

Human activities are disrupting ecosystem Human activities are disrupting ecosystem services that support and sustain all life and services that support and sustain all life and all economies.all economies.

A B CD

E

Which letter represents the stage in which shrubs grow?

Which letter represents the start of secondary ecological succession?

Which letter represents a mature forest of hardwoods?

Which letter represents the step in which perennial weeds and grasses are plentiful?

Which letter represents the stage in which the land can support trees, shrubs, weeds, and grasses?

Population biologists are concerned about introduced Population biologists are concerned about introduced species such as the zebra mussel in North species such as the zebra mussel in North America becauseAmerica because

a.a. Their removal from their native habitat has a Their removal from their native habitat has a negative impactnegative impact

b.b. Predators of the introduced species often Predators of the introduced species often overpopulate because of the influx of the overpopulate because of the influx of the introduced speciesintroduced species

c.c. The introduced species compete for resources The introduced species compete for resources more effectively than native speciesmore effectively than native species

d.d. Introduced species often become endangered in a Introduced species often become endangered in a new habitatnew habitat

e.e. Their introduction will require more land to be Their introduction will require more land to be protectedprotected

Which of the following is the best example of a Which of the following is the best example of a keystone specieskeystone species

a.a. Sea OtterSea Otter

b.b. Sea UrchinSea Urchin

c.c. Tree FrogTree Frog

d.d. Spotted OwlSpotted Owl

e.e. Snail DarterSnail Darter

Where is most of the world’s biodiversity?Where is most of the world’s biodiversity?

A.A. high-latitude forestshigh-latitude forests

B.B. Middle-latitude forestsMiddle-latitude forests

C.C. Low-latitude forestsLow-latitude forests

D.D. Polar grasslandsPolar grasslands

E.E. TundraTundra

How long does it take natural processes to How long does it take natural processes to produce fertile soil.produce fertile soil.

A.A. Weeks to monthsWeeks to months

B.B. Months to yearsMonths to years

C.C. Decades to a few centuriesDecades to a few centuries

D.D. Several centuries to several thousands of Several centuries to several thousands of yearsyears

E.E. Several thousand years to millions of yearsSeveral thousand years to millions of years

The tropical rain forest is characterized by all of The tropical rain forest is characterized by all of the following except highthe following except high

A.A. DiversityDiversity

B.B. ResilienceResilience

C.C. InertiaInertia

D.D. ConstancyConstancy

E.E. Persistence Persistence

Ecologists would consider all of the following to Ecologists would consider all of the following to be natural disturbances exceptbe natural disturbances except

A.A. DroughtsDroughts

B.B. FloodsFloods

C.C. DeforestationDeforestation

D.D. FiresFires

E.E. FrostFrost

chapter 8 community ecology. core case study: why should we care about the american alligator? ...

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