community ecology chapter 8. objectives summarize species types evaluate competition and predation...
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Community Ecology
Chapter 8
Objectives
• Summarize species types• Evaluate competition and predation• Compare and contrast symbiosis
What is a niche?
• Species’ way of life or functional role in an ecosystem
• Everything that affects its survival and reproduction– Range of tolerance for physical and chemical conditions– Types and amounts of resources it uses– How it interacts with other living and nonliving
components– Role it plays in energy flow and matter cycling
• How is this different from a habitat?
Fundamental vs. Realized
• Full potential range a species’ could theoretically use if no direct competition from other species
• Part of the fundamental niche a species actually uses
• Done to avoid competition for the same resources
Generalist vs. Specialist
• Have broad niche– Live in many places– Eat variety of food– Tolerate wide range of
environmental conditions
• Have narrow niche– Live in one type of
habitat– Only 1-2 types of food– Tolerate narrow range of
environmental conditions
Types of Species
• Native species
• Nonnative, exotic, or alien species
Types of Species
• Indicator
• Keystone
Why Should We Care About Alligators?
• Why are alligators considered a keystone species? How do they affect
• Do you think people should be allowed to kill alligators found on their property? Explain.
What might species compete for?
Intraspecific Competition
What makes a good territory?
Interspecific Competition
Interference Competition Exploitation Competition
Competitive Exclusion Principle
High
Low
Rel
ati
ve
po
pu
lati
on
den
sity
0 2 4 6 8 10 12 14 16 18
Days
Each species grown alone
Parameciumaurelia
Parameciumcaudatum
High
LowR
ela
tiv
e p
op
ula
tio
n d
ensi
ty0 2 4 6 8 10 12 14 16 18
Days
Both species grown together
Parameciumaurelia
Parameciumcaudatum
Reducing or Avoiding Competition
Why are Sharks Important?
Species Interaction
Who Benefits?
Who is Harmed? Examples
Predator-Prey
Parasitism
Mutalism
Commensalism
PredatorsIncrease Chance of Meal
PreyDefend or Avoid Predators
How is predation different from parasitism? How are they similar?
Objectives
• Explain community structure• Describe the theory of island biogeography
Community Structure
Ecotones and Edge Effects
Ants Birds
Latitude
Depth
Pollution
Spe
cie
s di
vers
ity 20
5
00 2,
000
4,000
6,000Depth (meters)
0 2,000 4,000 6,000
Depth (meters)
15
5
0
Coast Deep Sea
Snails Tube worms
Coast Deep Sea
0 2,000 4,000 6,000
Biod
iver
sity
Theory of Island BiogeographyHigh
Low
Ra
te o
f im
mig
ratio
no
r ex
tinct
ion
Equilibrium number
Immigration and extinction rates
Number of species on island
(a)
100
50
25
12.5
6.25
0 2,000 4,000 6,000 8,000 10,000
Distance from New Guinea (kilometers)
Num
ber
of
spec
ies
(per
cent
age
of
sam
ple
stu
died
)
100
1 10 100 1,000 10,000 100,000
Area (square miles)
Num
ber
of
amph
ibia
n an
d re
ptile
spe
cies
10
SABA MONTSERRAT CUBA
Hispaniola
Puerto Rico
Jamaica
Cuba
Montserrat
Saba
Redonda
Objectives
• Compare and contrast primary and secondary succession.
• Describe the factors that affect succession.• Evaluate the three types of stability
How do ecosystems respond to change?
• What happens after a forest fire?• What happens after a volcano?• What happens when climate changes?
Primary Succession
Secondary Succession
Succession and Wildlife
Primary Secondary
Primary or Secondary?
Disturbance and Succession
Intermediate Disturbance Hypothesis
Percentage disturbance
Spe
cies
div
ersi
ty
Succession Predictability
• Old View – predictable sequence leading to a climax community
• New View – ongoing process impacted by chance and biodiversity
Ecological Stability
• Inertia – persistence, resist change
• Constancy – maintain within limits, population
• Resilience – recover
Does diversity = stability?
Ecological Sustainability
• If diversity ≠ stability why conserve?
Precautionary principle
Succession, Disturbance and Stability
Draw a picture showing how disturbance can increase diversity. How is succession involved? How is stability involved?
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