1. All interactions between biotic factors that can impact an ecosystem
Community Ecology
All interactions between biotic factors that can impact an ecosystem

2. Community Ecology Basics
Population: One species in a specific area
Community: All biotic factors in a specific area
Ecosystem: All biotic and abiotic factors in an area

3. Community Members
Producers: organisms that produce their own food through photosynthesis or chemosynthesis
Autotrophs

4. Community Members Consumers: Organisms that consume their food
Heterotrophs, Detritivores
Carnivores, Omnivores, herbivores
Primary, secondary, tertiary, etc...

5. Can be organized into TROPHIC LEVELS
Community Members
Can be organized into TROPHIC LEVELS
Trends of survivorship can be found in Trophic levels

6. BIG IDEA
Community Ecology is the study of interactions between Community Members

7. Types of Interactions - Competition

8. Types of Interactions - Competition
Organisms attempting to use the same resource
Mates, food, territory (any need that must be filled for life)
Intraspecific Competition: between same species
Sexual selection
Interspecific Competition: between different species
Weeds vs garden plants

9. Types of Interactions - Competition
Competitive Exclusion Principle: no two species can occupy the same niche
Niche: organism’s role in an ecosystem
Includes habitat, food source, behavior (the sum of all biotic and abiotic interactions of an organism)

10. Types of Interactions - Competition
Result of Competition and CEP:
Population control
Extinction
Behavioral shift of one species
Long term evolutionary shift of one species
Character Displacement
If two similar species geographically overlap (sympatric populations), they will look more different than those than don’t overlap

11. Types of Interactions - Competition
Result of Competition and CEP:
Population control
Extinction
Behavioral shift of one species
Long term evolutionary shift of one species
Character Displacement
If two similar species geographically overlap (sympatric populations), they will look more different than those than don’t overlap

12. Types of Interactions - Predation

13. Types of Interactions - Predation
One organism hunts and eats another
Population growth can be affected by predation
Predator / Prey Population Density Cycles
One population’s growth responds to the other

14. Types of Interactions - Predation
Apex Predator: predator at the top of a food chain on which no other predators prey upon.
Mesopredator: Mid-level predator that preys upon and is preyed upon

15. Types of Interactions - Predation

16. Types of Interactions - Predation
Predation causes physical adaptations to both predator and prey due to natural selection

17. Types of Interactions - Predation
Prey Adaptation
Tend to be community oriented herd animals
Physical defensive and offensive adaptations
Adaptations specific to prey’s environment
Eye placement
Coloration
Cryptic
Aposematic
Mimicry

18. Types of Interactions - Predation
Prey Adaptation
Cryptic Coloration: Camouflage
Aposematic Coloration: indicates chemical warnings and defenses (poison)

19. Types of Interactions - Predation
Prey Adaptation
Batesian Mimicry: a harmless species look like a harmful one to avoid predation
Mullerian Mimicry: two or more distasteful species, mimic each other’s warning signals
Do not have to be closely related

20. Types of Interactions - Predation
Predator Adaptation:
Can be pack hunters or solo hunters
Acute senses
Physical Adaptations
Eye placement
Teeth
Feet
Speed
Cryptic Coloration

21. Types of Interactions - Herbivory

22. Types of Interactions - Herbivory
Type of predation in which autotrophs are eaten
Also results in defensive adaptations due to natural selection

23. Types of Interactions - Herbivory
Adaptive Results of Herbivory
Mechanical defense such as thorns and needles
Masting: producing more offspring than an animal can consume
Chemical defense that can include
Taste
Digestive absorption
Toxins
Repellents

24. Types of Interactions - Symbiosis

25. Types of Interactions - Symbiosis
A close and often long term interaction between two different species
Mutualism
Commensalism
Parasitism
Feeding relationships do not qualify as they are not long term

26. Types of Interactions - Symbiosis
Mutualism: Both species benefit from relationship
+ / +
Flowers and insects
Nemo and the Anemone
Result can be in increase in population

27. Types of Interactions - Symbiosis
Commensalism: one member benefits while the other is neither helped nor harmed
+ / 0
Egrets and Water Buffalo
Result can be an increase or stabilizing effect on one population and no effect on the other

28. Types of Interactions - Symbiosis
Parasitism: One organism lives in or on another and harms it in order to get what it needs to live
+ / -
Ticks and mammals
Result can be a limitation of one species population

29. Community Interactions can shape and impact an ecosystem in both positive and negative ways.
A Big Idea

30. Impact Through Trophic Interactions

31. Impact Through Trophic Interactions
Dominant Species
Species in a community that are the most abundant in number or biomass
Biomass = the total mass of all individuals in a population

32. Impact Through Trophic Interactions
How do species become dominant?
Superior in exploiting resources
Successful avoidance of predators or disease
Affects community by decreasing biodiversity or providing niche for other species
American Chestnut Tree

33. Impact Through Trophic Interactions
Keystone Species
Species that have a strong control over an ecosystem
Not based on numbers or biomass
Affects community by having large impact on other species

34. Impact Through Trophic Interactions
Keystone Species
Species that have a strong control over an ecosystem
Not based on numbers or biomass
Affects community by having large impact on other species

35. Impact Through Trophic Interactions
Foundation Species
Ecosystem engineers that impact trophic levels by providing habitats and niches for other species
Positively affect the reproduction and survival of other species

36. Changing Communities by changing trophic levels
Top Down and Bottom Up Models

37. Trophic Level Manipulation
Bottom Up Model: Biomass is altered at the lower trophic levels, allowing changes to move up the food web
Adding minerals to vegetation to stimulate growth
Top Down Model: Biomass is altered at the top trophic levels, allowing changes to move down the food web
Introducing a predator to control population of lower levels

38. Trophic Level Manipulation

39. Limits on Trophic Structure and Food Chain Length
Food Chain: transfer of food energy up trophic levels from source to eventually decomposers
Rarely more than 7 links
Most have 5 or fewer
Why?

40. Limits on Trophic Structure and Food Chain Length
Energetic Hypothesis: Inefficiency of energy transfer along trophic levels
Only 10% is transferred
Producer level consisting of 100 kg of plant matter can support 10 kg of herbivore biomass
This model predicts longer food chains in areas of high photosynthetic capability

41. Limits on Trophic Structure and Food Chain Length
Dynamic Stability Hypothesis: long food chains are less stable than short ones
Population fluctuations at lower trophic levels are magnified at higher levels
Cause potential extinction of top predators

42. Limits on Trophic Structure and Food Chain Length
Dynamic Stability Hypothesis: long food chains are less stable than short ones
Population fluctuations at lower trophic levels are magnified at higher levels
Cause potential extinction of top predators