1. Community and Ecosystem Ecology
Chapter 20

2. Community Ecology Species living in same vicinity
Potential interactions will occur
Interspecific interactions
Interactions between species
Classified according to effect on populations
Helpful (+)
Harmful (-)

3. Community Interactions
Occurs in a few ways:
Competition
Mutualism
Predation
Herbivory
Parasites and pathogens

4. 1. Competition (-/-)
Occurs when members of two different species try to utilize the same resource
Competitive Exclusion Principle:
No two species can occupy the same ecological niche at the same time

5. Competition Between Two Species of Barnacles

6. Competition Competition can lead to resource partitioning
decreases competition between the two species
Character displacement is often viewed as evidence that competition and resource partitioning have taken place

7. 2. Mutualism (+/+)
Both members of the association benefit

8. 3. Predation (+/-) Predator Prey
2 ways this regulates population growth:
A. Predator-Prey Population Dynamics
B. Antipredator Defenses

9. 3. Predation A. Predator-Prey Population Dynamics
Cycling of predator and prey populations
Occurs when either predators overkill prey, or when prey overuse resources and their numbers crash
In either case, predator numbers also decrease from a decrease in food source

10. Predatory-Prey Cycling of a Lynx and a Snowshoe Hare

11. Coevolution
Evolutionary change in one species results in an evolutionary change in the other
Organisms in symbiotic associations are especially prone to the process of coevolution
Also occurs between predators and prey
Example: Cheetah sprints forward to catch prey, and this behavior might be selective for those gazelles that jump high in the air

12. 3. Predation B. Antipredator Defenses Cryptic coloration
Camouflage
Warning coloration
Association with undesirable consequences

13. 3. Predation B. Antipredator Defenses Mimicry
One species resembles another species
Can help capture food or avoid being preyed upon
Batesian Mimicry
A prey that is not harmful mimics another species that has a successful antipredator defense
Warning colorations
Mullerian mimicry
Species that resemble each other all have successful defenses

14. Mimicry Among Insects
Mullerian
Batesian

15. Coral snake vs. Milk snake

16. 4. Herbivory (+/-) Consumption of plants by an animal
Plant must expend energy to regenerate
Evolved defenses

17. 5. Parasites & Pathogens (+/-)
Lives on or in a host
Endoparasite
Ectoparasite
Pathogens
Disease-causing microorganisms

18. Trophic Structures Feeding relationships among species in a community
Determines the passage of energy and nutrients
Sequence of food transfer is a food chain
Unbranched

19. Trophic Structure Autotrophs (producers)
Require an energy source and inorganic nutrients to produce organic food molecules
Manufacture organic nutrients for all organisms
Green plants and algae carry on photosynthesis

20. Trophic Structure Heterotrophs (consumers)
Need a preformed source of organic nutrients
Herbivores
Graze directly on plants or algae
Carnivores
Feed on other animals
Omnivores
Feed on both plants and animals

21. Trophic Structure Heterotrophs Decomposers Scavengers
Heterotrophic bacteria and fungi
Break down nonliving organic matter
They release inorganic matter to be used by producers
Scavengers
Feed on dead remains

22. Ecosystem

23. Ecosystem Ecology Possesses both abiotic and biotic components Biotic
The various populations of organisms that form a community
Abiotic
Includes resources such as sunlight, inorganic nutrients, soil, water, temperature and wind
Two major processes sustain all ecosystems:
Energy flow
passage of energy through the components of the ecosystem
Chemical cycling
use and reuse of chemical elements within the ecosystem

24. Light energy Chemical energy Heat energy Chemical elementscy cl in g
Energy flow
Light
energy
Chemical
energy
Heat
energy
Figure A terrarium ecosystem
Chemical
elements
Bacteria,
protists,
and fungi

25. Energy Flow Ecological Pyramids Biomass
Mass of living organic material in ecosystem
Ecological Pyramids
only about 10% of the energy of one trophic level is available to the next trophic level
Producers at the base
Most available energy
Energy is given off in less usable forms as producers are eaten by primary consumers, etc.

26. Chemical Cycling Biogeochemical cycles
Biotic and abiotic components of the chemical cycles in an ecosystem
3 main cycles:
Carbon cycle
Phosphorus cycle
Nitrogen cycle

27. Figure 20.32 CO2 in atmosphere Burning Photosynthesis
Cellular respiration
Higher-level
consumers
Plants, algae,
cyanobacteria
Wood
and fossil
fuels
Primary
consumers
Figure The carbon cycle
Decomposition
Wastes; death
Plant litter;
death
Decomposers
(soil microbes)
Detritus
Figure 20.32