1. Which species benefits from its interactions?
Community Ecology
Which species benefits from its interactions?

2. Community Ecology Review
Community interactions are classified by whether they help, harm, or have no effect on the species involved
Examples are competition, predation, herbivory, symbiosis (parasitism, mutualism, and commensalism), and facilitation

3. Community Ecology Review
Ecological Niche: Abiotic and biotic factors that an organism uses to live.
Species can coexist in a community if there are one or more significant differences in their niches

4. A species’ fundamental niche is the niche potentially occupied by that species
A species’ realized niche is the niche actually occupied by that species
As a result of competition, a species’ fundamental niche may differ from its realized niche
For example, the presence of one barnacle species limits the realized niche of another species

5. EXPERIMENT High tide Chthamalus Chthamalus Balanus realized niche
Figure 54.3
EXPERIMENT
High tide
Chthamalus
Balanus
Chthamalus
realized niche
Balanus
realized niche
Ocean
Low tide
RESULTS
High tide
Figure 54.3 Inquiry: Can a species’ niche be influenced by interspecific competition?
Chthamalus
fundamental niche
Ocean
Low tide

6. Diversity and trophic structure characterize biological communities
The type of organism in a community and resources they use characterize an ecosystem.
Species diversity (Biodiversity) of a community is the variety of organisms that make up the community
It has two components: species richness and relative abundance
Species richness is the number of different species in the community
Relative abundance is the proportion each species represents of all individuals in the community

7. Which Forest is more diverse?
Figure 54.10 A B C D
Community 1
Community 2
Figure Which forest is more diverse?
A: 25%
B: 25%
C: 25%
D: 25%
A: 80%
B: 5%
C: 5%
D: 10%
Which Forest is more diverse?

8. Biodiversity Communities with higher diversity are
More productive and more stable in their productivity
Better able to withstand and recover from environmental stresses
More resistant to invasive species, organisms that become established outside their native range

9. Trophic Structures
Trophic structure is the feeding relationships between organisms in a community
Food chains link trophic levels from producers to top carnivores

10. A terrestrial food chain A marine food chain
Figure 54.13
Carnivore
Quaternary
consumers
Carnivore
Carnivore
Tertiary
consumers
Carnivore
Carnivore
Secondary
consumers
Carnivore
Figure Examples of terrestrial and marine food chains.
Herbivore
Primary
consumers
Zooplankton
Plant
Primary
producers
Phytoplankton
A terrestrial food chain
A marine food chain

11. Label teach organisms trophic level in this food web? Fish larvae
Figure 54.15
Sea nettle
Juvenile striped bass
Figure Partial food web for the Chesapeake Bay estuary on the U.S. Atlantic coast.
Label teach organisms trophic level in this food web?
Fish larvae
Fish eggs
Zooplankton

12. Energy Transfer with Trophic structures
The energetic hypothesis state that: length is limited by inefficient energy transfer
For example, a producer level consisting of 100 kg of plant material can support about 10 kg of herbivore biomass (the total mass of all individuals in a population)
The dynamic stability hypothesis states that: long food chains are less stable than short ones
Most data support the energetic hypothesis

13. Number of trophic links
Figure 54.16 5 4 3
Number of trophic links 2 1
High (control):
natural rate of
litter fall
Medium: 1/10
natural rate
Low: 1/100
natural rate
Figure Test of the energetic hypothesis for the restriction of food chain length.
Productivity