Download The Interactions of Different Populations I. What is a Community?

Chapter 54.1-2 Community Ecology: The Interactions of Different Populations
I. What is a Community?
- An assemblage of species living
close enough together for potential
interaction.
What forms the community structure?
II. Interspecific Interactions!
- A competition for resources between
individuals of two or more species when
resources are in short supply; detrimental
to both species (-/-)
A. Competition ( - / - )
- Interaction detrimental to both species
B. Competitive Exclusion Principle
Two species with similar needs for same limiting resources cannot coexist in
the same place. Example - Paramecium
C. Ecological Niche
An organism’s role in the environment.
-Sum total of an organism’s use of abiotic/biotic resources in the environment.
-The Competitive Exclusion Principle can be restated to say that two species
cannot coexist in a community if their niches are identical.
1. Fundamental Niche
-Niche that is possible for
the organism due to abiotic
conditions
2. Realized Niche
- Niche that results due to
biotic interactions
D. Resource Partitioning
-differentiation of niches that
enables two similar species to
coexist in a community.
E. Character Displacement
-the tendency for characteristics to be
more divergent in sympatric
populations of 2 species than
allopatric populations of same 2
species
Character Displacement
(don’t focus on too much, will see again in evolution unit)
-Allopatric
means
geographically
separate;
sympatric
means
geographically
overlapping
-both birds eat
similarly sized
seeds on Los
Hermanos and
Daphne
islands.
-Difference in
beak
morphology
show
adaptations that
favor eating
different-sized
seeds
F. Predation Types ( + / - )
1) “Standard”
( + / - ) predator eats prey that is immediately consumed
2) Herbivory
(+ / - ) animal eats plant
(+ / - ) predators live on (ectoparasite) /or in (endoparasite) a
host and depend on the host for nutrition
4) Parasitoidism (+ / - ) special type of parasitism where the parasite
eventually kills the host
http://www.youtube.com/watch?v=Df_iGe_JSzI
3) Parasitism
G. Prey Defenses
1) Cryptic Coloration
camouflage including deceptive markings.
2) Aposematic Coloration warning colors, that is sometimes
associated with other defenses (toxins).
3) Batesian Mimicry
harmless species mimics a harmful one
4) Mullerian Mimicry
two or more unpalatable species resemble each other
H. Symbiosis
1) Mutualism
(+/+)
2) Commensalism ( + / 0 )
two species benefit from their interaction
one species benefits from the
interaction, but other is not
affected.
Vocab Quiz
III. Species Diversity – 2 components
-the variety of different kinds of organisms that make up the community
A. Species Richness
-the number of different species in the community
B. Relative Abundance
-the proportion each species represents of all
individuals in the community
H=0.71
H=1.39
C. Measure using Shannon diversity (H)
D. Diversity & Community Stability
-the higher the value H, the more diverse community
-more resistant to invasive species (organism
established outside native area), more resistant to
disturbance/stress (drought, fire, flood), and are more
productive (more biomass, meaning total mass of all
organisms in a habitat)
IV. Trophic Structure
A. Food Chains
B. Food Webs
determines the feeding relationships between organisms
transfer of food energy from its source in photosynthetic organisms
through herbivores and carnivores
All trophic relationships diagrammed in a
community; interconnecting food chains
C. Dominant Species
-have the highest abundance or highest biomass (the sum weight of all individuals in a population)
D. Keystone Species
-exert an important regulating effect on other species in a community
E. Ecosystem Engineers
-an organism that influences community structure by causing physical changes to
the environment
Nellie the otter
V. How is Community Structure controlled?
N = minerals/nutrients
A. Bottom-up model
V = vegetation
H = herbivores
P = predators
-unidirectional influence from lower to higher trophic levels
NVHP
B. Top-down model
-predation controls community organization because
predators limit herbivore numbers, which in turn control
plant/phytoplankton numbers, which in turn control nutrient
levels (aka trophic cascade model)
NVHP
Slide 3
Slide 3
Slide 3
Which community relationship is demonstrated by each of the pictures below?
A: Commensalism
D: Batesian Mimicry
G Herbivory
B: Parasitoidism
E: Mullerian Mimicry
H: Aposematic Coloration
C: Mutualism
F: Cryptic Coloration
I: Batesian Mimicry
Slide 3
Gause’s experiment that led to
idea of Competitive Exclusion
Slide 1