Community Ecology, Population Ecology, And Sustainability
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8/3/2019 Community Ecology, Population Ecology, And Sustainability
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Community Ecology, Population
Ecology, and Sustainability
Chapter 6
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Key Concepts Factors determining number of species in a
community
Roles of species Species interactions
Responses to changes in environmental
conditions Reproductive patterns
Major impacts from humans
Sustainable living
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Community Structure and Species
Diversity Physical appearance
Edge effects
Species diversity or richness
Species abundance or evenness
Niche structure
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Fig. 6-2, p. 110
Natural Capital: Types, Sizes, and
Stratification of Terrestrial Plants
Tropicalrain forest
Coniferousforest
Deciduousforest
Thornforest
Thornscrub
Tall-grassprairie
Short-grassprairie
Desertscrub
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Species Diversity and Ecological
Stability Many different species provide ecological stability
Some exceptions
Minimum threshold of species diversity
Many unknowns
Net primary productivity (NPP)
Essential and nonessential species
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Types of Species Native
Nonnative (invasive or alien)
Indicator
Keystone
Foundation
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Indicator Species Provide early warnings
Indicator of water quality
Birds as environmental indicators
Butterflies
Amphibians
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Amphibians as Indicator Species
Environmentally sensitive life cycle
Vulnerable eggs and skin
Declining populations
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sperm
Eggs
Sexualreproduction
Fertilized eggdevelopment Organ formation
Egg hatches
Tadpole
Tadpole develops intofrog
Young frogAdult frog(3 years)
Fig. 6-3, p. 112
Life Cycle of a Frog
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Possible Causes of Declining
Amphibian Populations
Habitat loss and fragmentation
Prolonged drought
Pollution
Increases in ultraviolet radiation
Parasites
Overhunting
Disease
Nonnative species
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Why Should We Care about
Vanishing Amphibians?
Indicator of environmental health
Important ecological roles of amphibians
Genetic storehouse for pharmaceuticals
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Keystone Species
What is a keystone?
Keystone species play critical ecological roles
Pollination
Top predators
Dung beetles
Sharks
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Foundation Species
Relationship to keystones species
Play important roles in shaping communities
Elephants
Contributions of bats and birds
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Species Interactions Interspecific competition
Predation
Parasitism
Mutualism
Commensalism
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Species Interactions: Competition
Interspecific Competition
Fundamental niches
Fighting for limited resources
Competition from humans
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Reducing or Avoiding Competition
Resource partitioning
Role of natural selection
Specialization and sharing of resources
Resource partitioning of warblers
R P i i i d Ni h
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N u
m b e r o f i n d i v i d u a l s
N u m b e r o f i n d i v i d
u a l s
Resource use
Resource use
Species 1 Species 2
Region
ofniche overlap
Species 1 Species 2
Resource Partitioning and NicheSpecialization
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Resource Partitioning of Warbler
Species
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Predator and Prey Interactions Carnivores and herbivores
Predators
Prey
Natural selection and prey populations
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How Do Predators Increase Their
Chances of Getting a Meal? Speed
Senses
Camouflage and ambush
Chemical warfare (venom)
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Avoiding and Defending Against
Predators Escape
Senses
Armor
Camouflage
Chemical warfare
Warning coloration
Mimicry
Behavior strategies
Safety in numbers
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Span worm Bombardier beetle
Viceroy butterfly mimicsmonarch butterfly
Foul-tasting monarchbutterfly
Poison dart frog When touched, thesnake caterpillarchanges shape to looklike the head of a snake
Wandering leaf insect
Hind wings of io mothresemble eyes of amuch larger animal
Fig. 6-6, p. 116
How Species Avoid Predators
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Parasites
Parasitism
Hosts
Inside or outside of hosts
Harmful effects on hosts
Important ecological roles of parasites
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Mutualism
Both species benefit
Pollination
Benefits include nutrition and protection
Mycorrhizae
Gut inhabitant mutualism
E l f M li
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Oxpeckers and black rhinoceros Clown fish and sea anemone
Lack of mycorrhizae fungi onjuniper seedlings in sterilized soil Fig. 6-7, p. 117
Examples of Mutualism
© 2006 Brooks/Cole - Thomson
Mycorrhizae fungi on juniperseedlings in normal soil
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Commensalism Species interaction that benefits one
and has little or no effect on the other
Example: Small plants growing in
shade of larger plants
Epiphytes
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Bromeliad Commensalism
Fig. 6-8, p. 118
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Ecological Succession:
Communities in Transition
What is ecological succession?
Primary succession
Secondary succession
P i E l i l S i
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Fig. 6-9, p. 119
Small herbsand shrubs
Heath mat
Jack pine,black spruce,
and aspen
Balsam fir, paper
birch, and whitespruce climaxcommunity
Exposedrocks
Lichensand mosses
Primary Ecological Succession
S d E l i l S i
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Fig. 6-10, p. 120
Annualweeds
Perennialweeds and
grasses
Shrubsand pineseedlings
Young pine forest withdeveloping understory
of oak and hickorytrees
Mature oak-hickory forest
Secondary Ecological Succession
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How Predictable is Succession?
Climax community concept
“Balance of nature”
New views of equilibrium in nature
Unpredictable succession
Natural struggles
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Population Dynamics: Factors
Affecting Population Size
Population change = (births + immigration)
– (deaths + emigration)
Age structure (stages)
Age and population stability
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Limits on Population Growth
Biotic potential
Intrinsic rate of increase ( r)
No indefinite population growth
Environmental resistance
Carrying capacity ( K )
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Exponential and Logistic Population
Growth Resources control population growth
Exponential growth
Logistic growth
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Fig. 6-11, p. 121
Carrying capacity (K )
Environmental
resistance
Bioticpotential
Exponentialgrowth
Population Growth Curves
Time (t )
P o p u l a t i o n s
i z e ( N )
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Fig. 6-12, p. 121
Logistic Growth of Sheep Population
Overshoot Carrying Capacity
Year
N
u m b e r o f s h e e
p ( m i l l i o n s )
2.0
1.5
1.0
.5
1800 1825 1850 1875 1900 1925
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When Population Size Exceeds
Carrying Capacity
Switch to new resources, move or die
Overshoots
Reproductive time lag
Population dieback or crash
Famines among humans
Factors controlling human carrying capacity
Exponential Growth Overshoot and
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Exponential Growth, Overshoot and
Population Crash of Reindeer
Fig. 6-13, p. 122
PopulationOvershootsCarryingCapacity
Populationcrashes
Carrying
capacity
Year
N
u m b e r o f s h e e
p ( m i l l i o n s ) 2,000
1,500
1,000
500
01910 1920 1930 1940 1950
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Reproductive Patterns
r-selected species
Opportunists (mostly r-selected)
Environmental impacts on opportunists
K-selected species (competitors)
Intermediate and variable reproductive patterns
P i i f l d d K l d S i
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Carrying capacity
K species;experienceK selection
r species;
experiencer selection
K
Fig. 6-14, p. 122
Positions of r-selected and K-selected Species on
Population Growth Curve
Number of individuals
Time
N u
m b e r o f i n d i v i d u
a l s
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Fig. 6-15, p. 123
r-selected Opportunists and K-selected Species
S l t d S i
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r-Selected Species
Cockroach
Dandelion
Many small offspring
Little or no parental care and protection of offspring
Early reproductive age
Most offspring die before reaching reproductive age
Small adults
Adapted to unstable climate and environmental conditions
High population growth rate (r )
Population size fluctuates wildly above and below carrying capacity (K )
Generalist niche
Low ability to compete
Early successional species
Fig. 6-15a, p. 123
r-selected
Opportunists and
K-selected Species
K S l t d S i
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Fewer, larger offspring
High parental care and protection of offspring
Later reproductive age
Most offspring survive to reproductive age
Larger adults
Adapted to stable climate and environmental conditions
Lower population growth rate (r )
Population size fairly stable and usually close to carrying capacity (K )
Specialist niche
High ability to compete
Late successional species
ElephantSaguaro
K-Selected Species
Fig. 6-15b, p. 123
r-selected
Opportunists and
K-selected Species
Characteristics of Natural and Human
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Fig. 6-16, p. 124
Property Natural Systems Human-DominatedSystems
Complexity
Energy source
Waste production
Nutrients
Net primaryproductivity
Biologically diverse
Renewable solarenergy
Little, if any
Recycled
Shared among manyspecies
Biologicallysimplified
Mostly nonrenewablefossil fuel energy
High
Often lost of wasted
Used, destroyed, ordegraded to supporthuman activities
Characteristics of Natural and Human-
Dominated Systems
Human Impacts on Ecosystems
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Fig. 6-17, p. 125
Reduction of biodiversity
Increasing use of the earth'snet primary productivity
Increasing genetic resistanceof pest species and diseasecausing bacteria
Elimination of many naturalpredators
Deliberate or accidentalintroduction of potentiallyharmful species intocommunities
Using some renewableresources faster than they canbe replenished
Interfering with the earth'schemical cycling and energyflow processes
Relying mostly on polluting
fossil fuels
Human Impacts on EcosystemsNatural Capital Degradation
Altering Nature to Meet Our Needs
Four Principles of Sustainability
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Fig. 6-18, p. 126
Four Principles of Sustainability
PRINCIPLESOF
SUSTAINABILITY
Solutions
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Runs onrenewablesolar energy.
Recyclesnutrientsand wastes.There is littlewastein nature.
Uses biodiversityto maintain itselfand adapt to newenvironmentalconditions.
Controls aspecies'population size
and resource useby interactionswith itsenvironmentand otherspecies.
Rely mostly onrenewable solarenergy.
Prevent andreducepollution andrecycleand reuseresources.
Preservebiodiversityby protectingecosystemservices andpreventingprematureextinctionof species.
Reduce birthsandwasteful resourceuse to preventenvironmentaloverload anddepletion anddegradation ofresources.
Fig. 6-19, p. 126
Solutions: Implications of the Principles
of Sustainability
Principles of Sustainability
How Nature Works Lessons for Us
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Lessons from Nature We are dependent on the Earth and Sun
Everything is interdependent with everything else
We can never do just one thing
Earth’s natural capital must be sustained
Precautionary Principle
Prevention is better than cure
Risks must be taken
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