1. Community Characteristics
Chapter 27
Community Characteristics

2. Why do organisms compete?
Food, resources and reproduction

3. 27.1 Biotic Factors Nutritional Relationships
*Predator-prey relationship
*Interspecies Competition
*Intraspecies Competition
Symbiotic Relationships
*Mutualism (+,+)
*Parasitism (+, -)
*Commensalism (+,0)

4. SPECIES A
SPECIES B
Positive
Negative
Neutral

5. Resource partitioning
SPECIES A
SPECIES B
Positive
Negative
Neutral
mutualism
Predation (Species A is prey)
Parasitism (Species A is host)
Competitive exclusion of Species A
commensalism
Predation (Species A is predator)
Parasitism (Species A is parasite)
Competition
Limiting resources --
Resource partitioning

6. 2. Symbiotic Relationships
Different organisms may live together in a close association.
This is known as symbiosis.
There are three types:
1. Commensalism 2. Mutualism 3. Parasitism
KEY:
+ = benefits
- = harmed
o = not affected

7. Ex: barnacles on a whale
Commensalism
(+ , o)
In this relationship, one organism benefits and the other is not affected.
Ex: barnacles on a whale

8. Commensalism
(+ , o)
Epiphytes (mosses, orchids, ferns, bromeliad ) attach themselves to tree bark and obtain their nutrients without harm to the trees.

9. Mutualism
(+ , +)
In this relationship both organisms benefit from each other.
Ex: protozoan living in the digestive tract of termites.
Wood eaten by termites is digested by the protozoan. The nutrients released supply both organisms.

10. In this relationship both organisms benefit from each other.
Mutualism
(+ , +)
In this relationship both organisms benefit from each other.
Ex:

11. Mycorrhizae (+ , +)
In this relationship both organisms benefit from each other.
Ex: Red Cedar and mycorrhizal fungi.

12. Ex: athlete’s foot fungus on humans tapeworm and heartworm in dogs.
Parasitism
(+ , - )
In this relationship, the parasite benefits at the expense of the host.
Ex: athlete’s foot fungus on humans
tapeworm and heartworm in dogs.

13. Crown gall disease in plants.
Parasitism
(+ , - )
Pathogens (disease causing agents) are parasites that often cause the death of its host.
Crown gall disease in plants.

14. Parasite/Host Relationship
Guinea worm/Human

15. Parasite/Host Relationship
Sea Lamprey/Fish

16. Parasitism Parasite/Host Relationship Varroa mite/Honeybee
Tracheal mites

17. Do Now:
Define keystone species and discuss two examples of organisms that are keystone species.

18. Keystone species
These determine the nature and structure of an entire ecosystem. Usually found in small numbers but have a key influence.
Examples: Wolves, Fig Trees

19. 27.4 Predator/Prey Relationships!

20. 27.4 Predator-Prey Cycles

21. 27.7 Predator/Prey Relationships
Data collected from fur pelts from the Hudson Bay Company

22. Studies have shown that Endocrine changes in populations may produce behavioral changes which tend to limit population growth. Therefore all population changes may not be due to predator/prey relationships alone.

23. by Margaret Carroll Department of Biology Framingham State College
Case Study
"The Effects of Coyote Removal in Texas: A Case Study in Conservation Biology"
by Margaret Carroll Department of Biology Framingham State College

24. Case Study
The Wolf, the Moose, and the Fir Tree: Who Controls Whom on Isle Royale? A case study of trophic interactions by Gary M. Fortier Department of Small Animal Science Delaware Valley College

25. The Data

26. The Data
Fig. 1. Population parameters of the Isle Royale ecosystem from Shaded areas signify periods of forage suppression that may be connected to interactions between herbivores and carnivores.
Population size of wolves each winter (based on aerial counts).
Population size of moose each winter (based on aerial counts and skeletal remains).
Ring-widths from the west end of Isle Royale, N=8.
Ring-widths from the east end of Isle Royale, N=8.
Actual evapotranspiration rates (AET), annual calculations based on data from April-October at a weather station 20 km from Isle Royale. AET is an approximation of primary productivity, it represents water availability as a function of temperature and rainfall.

27. Energy Flow Relationships
For an ecosystem to be self-sustaining, there must be a flow of energy between organisms.
The pathway of energy flow through the living components of an ecosystem are represented by food chains and food webs.
          

28. Nutritional Relationships
Involves the transfer of nutrients from one organism to another within an ecosystem.
In terms of nutrition, organisms are either autotrophs or heterotrophs

29. Energy Flow through a food Chain

30. Energy Losses The mouse receives energy from the food it eats.
Cells extract the food's energy for growth, acquiring food, escaping enemies lost as heat. Some lost in the mouse's waste (feces).
The remaining energy is stored in the mouse's body and is available to the organism that preys on it.
About 90% of the energy is used or lost, only 10% is available to predators.

31. Energy Flow

32. Biological Magnification
A nondegradable or slowly degradable substance
That becomes more and more concentrated in the tissues of organisms at higher trophic levels of a food web.
* Dichloro-Diphenyl-Trichloroethane (DDT)
* Polychlorinated biphenyls (PCBs)

33. DDT in Food Webs

34. DDT

35. PCBs in Food Webs
PCB concentrations in animal tissue can be magnified up to 25 million times.
Microscopic organisms pick up chemicals from sediments
Consumed in large numbers by filter feeding zooplankton.
Mysid shrimp then consume zooplankton
fish eat the mysid
and so on up the food web to the herring gull.
(Figure and caption from Our Stolen Future, p. 27)

36. DDT residues Why was there never a concern for the Ring-billed gulls?
Fig. 41-7, p.736

37. DDT Detection
In 1962, Rachel Carson, a former U.S. Fish and Wildlife Service (USFWS) scientist and writer, published Silent Spring, outlining the dangers of DDT
Fig. 41-8, p.736

38. DDT in Food Webs Heinz Meng
Responsible for the reintroduction of the Peregrine Falcon.

39. 27.3 Competitive Interactions
Exploitative competition: species do not interact directly but compete for resources
Competitive exclusion: both species require same resource

40. 27.3 Competitive Interactions WAYS TO AVOID COMPETITION ???
Over abundance or resources
Resource Partitioning

41. 27.3 Natural selection can favor Resource Partitioning: differences in resource use among species.

42. The diagram represents a tree containing three different species of warbler, A, B, and C. Each species occupies a different niche. A fourth species, D, which has the same environmental requirements as species B, enters the tree at point X. Members of species B will most likely 
(1.) live in harmony with species D 
(2.) move to a different level and live with species A or species C 
(3.) stay at that level but change their diet 
(4.) compete with species D

43. Effect of community complexity on Species richness

44. 41.8 Ecological Succession
Succession is a process of ecological change in which a series of natural communities are established and then replaced over time.
Two kinds of succession: .
Primary succession takes place on an area that is originally completely empty of life.
flow of lava has, for a time, no life at all on it.
Over a period of time, however, various kinds of organisms begin to grow in the area. Over time, the variety of life-forms changes as succession continues.
Secondary succession is far more common. It occurs in an area where life once existed but has then been destroyed.
a forest that has been destroyed by a wildfire.
For a period of time, no living organisms may exist in the area. Before long, however, certain types of plants begin to reappear. And, as with primary succession, the nature of the plant communities gradually change over time.

45. 41.8 Ecological Succession
Pioneers
Organisms
-lichen
-grasses
Climax
Community

46. United streaming video
Biologix: Interactions and Relationships among Organisms