Transcript Dec 6 - University of San Diego

Fig. 53.9
Fig. 53.10
Soay Sheep – Hirta Island
I.
Population Ecology
D.
Population Dynamics
3.
Life History Strategies
•
Finite amount of energy to allocate among growth,
reproduction, metabolism
•
Some species maximize reproduction; others
maximize survival
a. r-selection
•
Opportunistic species in variable environments
•
Population usually much higher or much lower
than carrying capacity
•
Many weed/pest species
b. K-selection
•
Usually in stable environments
•
Population usually at/near carrying capacity
•
Many endangered species Why?
I.
Population Ecology
D.
Population Dynamics
4.
Factors Affecting Population Growth/Size
a.
b.
Density-Independent Factors
•
Catastrophic events
•
Ex: Floods, fires, drought, storms, extreme weather
•
Some aggregated organisms and social animals can
enhance resistance to density-independent factors
•
Ex: Emperor penguins, clustered plants/animals
Density-Dependent Factors
•
Effects increase as population size increases
1. Competition – Limit = resources (food, water, etc.)
Territoriality – Limit = space availability
1. Health – Includes disease
2. Predation – Selective by predator(s)
3. Wastes – Toxic at higher concentrations
4. Other Factors – Ex: Aggression at higher densities
Soay Sheep – Hirta Island
Fig. 53.16
I.
Population Ecology
D.
Population Dynamics
4.
Factors Affecting Population Dynamics
a.
b.
Density-Independent Factors
•
Catastrophic events
•
Ex: Floods, fires, drought, storms, extreme weather
•
Some aggregated organisms and social animals can
enhance resistance to density-independent factors
•
Ex: Emperor penguins, clustered plants/animals
Density-Dependent Factors
•
Effects increase as population size increases
1. Competition – Limit = resources (food, water, etc.)
2. Territoriality – Limit = space availability
3. Health – Includes disease
4. Predation – Selective by predator(s)
5. Wastes – Toxic at higher concentrations
6. Other Factors – Ex: Aggression at higher densities
I.
Population Ecology
D.
Population Dynamics
5.
Population Stability
•
a.
Stability usually related to lifespan, reproductive rate
Environmental factors
•
Resource availability
•
Recruitment
Isle Royale
Fig. 53.18
I.
Population Ecology
D.
Population Dynamics
5.
Population Stability
•
a.
Stability usually related to lifespan, reproductive rate
Environmental factors
•
Resource availability
•
Recruitment
b. Immigration
•
Metapopulations may be more stable than
isolated populations
Glanville Fritillary
Fig. 53.21
I.
Population Ecology
D.
Population Dynamics
5.
Population Stability
•
a.
Stability usually related to lifespan, reproductive rate
Environmental factors
•
Resource availability
•
Recruitment
b. Immigration
•
Metapopulations may be more stable than
isolated populations
c. Combined factors
•
Resources, predation, etc.
Fig. 53.19
II.
Community Ecology
•
Focus on interspecific interactions
•
A.
May be direct or indirect
Competition
•
Two or more species competing for scarce
resource
•
•
1.
Ex: Two plant species competing for water
May be detrimental to one or both species
Competitive exclusion
•
•
No two species can use same set of resources in
same area at same time
Competitively dominant species tend to force
extinction of competitively inferior species
II.
Community Ecology
A.
Competition
2.
Ecological niche
•
•
•
•
Species’ ecological role in a community
Includes use of abiotic and biotic resources
Niche occupied by a species may be narrower than
range of conditions tolerated by species
Fundamental niche vs. realized niche
Fig. 54.3
II.
Community Ecology
A.
Competition
3.
Resource partitioning
•
•
Competitive exclusion can be minimized if
competing species modify niches to reduce overlap
Usually involves dividing resource
Anolis
Dominican
Republic
Fig. 54.2
II.
Community Ecology
A.
Competition
4.
Character displacement
•
•
Resource partitioning may lead to directional
selection on one or both species
Directional selection may lead to divergence in traits
Fig. 54.4
II.
Community Ecology
B.
Predation
•
•
Involves consumption of prey by predator
Predator usually has adaptations to facilitate capture of
prey
Natural selection acts on both predator and prey
•
•
1.
Coevolution
Strategies
a.
b.
c.
Pursuit predation
•
Predators chase prey to capture them
•
Predator usually faster, stronger, &/or more agile than
prey
•
Some species hunt in groups
Ambush predation
•
Predators lie in wait for prey
•
Predators usually camouflaged or concealed
•
May involve lures
Aggressive mimicry
•
Ex: Bolas spider mimics odor of female moths to
attract male moths
II.
Community Ecology
B.
Predation
2.
Predator avoidance
a.
Escape
•
Running/Swimming/Flying away
b. Mechanical defenses
•
Ex: Porcupine quills, armadillo armor
c. Social behavior
•
Ex: Schooling, standing watch
d. Chemical defenses
•
Ex: Poison dart frog, skunk
e. Defensive coloration
Cryptic coloration
- Canyon tree frog
Aposematic coloration
- Poison dart frog
Müllerian mimicry
Batesian mimicry
Fig. 54.5
II.
Community Ecology
C.
Herbivory
•
•
Consumption of plants by animals
Most herbivores are small
•
•
•
Ex: Insects, snails/slugs
Herbivores adapted to consume plants
Some plants have anti-herbivore defenses
•
•
•
Physical – Ex: Thorns, spines
Chemical – Ex: Nicotine in tobacco, pyrethrins in
chrysanthemums
Coevolution has affected herbivore evolution
•
Ex: Monarch butterfly caterpillars can eat milkweed
•
Toxic to most herbivores
•
Nearly exclusive access to food source
•
Can sequester noxious compounds for defense
II.
Community Ecology
D.
Parasitism
•
Parasite benefits at expense of host
•
•
Fig. 33.12
•
•
•
•
Host harmed in process
Ex: Tapeworm absorbs nutrients from host digestive
system
Endoparasites – Live within body of host
Ectoparasites – Live outside body of host
Parasitoids – Lay eggs on/in host; larvae feed
on host, eventually killing host
Many parasites have complex life cycles
Fig. 33.11
Schistosoma mansoni
II.
Community Ecology
E.
Disease
•
Widespread disease outbreaks may alter
community composition and dynamics
•
•
•
•
Ex: Dutch elm disease
Ex: Sudden oak death
Ex: Avian flu
Ex: West Nile virus