COMMUNITY ECOLOGY

1. COMMUNITY ECOLOGY CHAPTER 8

2. I. Community Structure A. FOUR CHARACTERISTICS 1. Physical Appearance Size, Stratification, Distribution of populations/ species 2. Species Diversity or Richness Number of different species 3. Species Abundance Number of individuals of each species 4. Niche Structure Number of ecological niches

3. The types, relative sizes, and stratification of plants and animals vary in different terrestrial communities and biomes. • Distribution of populations and species in a terrestrial or aquatic community can be vertical or horizontal • -In terrestrial ecosystems physical structure is usually a mosaic ofVEGETATION PATCHESwith sharper edges and wider ecotones • EDGE EFFECTS – Differences in the physical structure and physical properties at boundaries and ecotones.

4. 100 30 20 50 10 ft m Tropical rain forest Coniferous forest Deciduous forest Thorn forest Thorn scrub Tall-grass prairie Short-grass prairie Desert scrub Community Structure: Appearance and Species Diversity Fig. 8.2, p. 174

5. II. THE EXTENT of BIODIVERSITY BIODIVERSITY- term used to indicate the number and types of organisms on the earth/in an area. Studies indicate that the most species rich environments are… -Tropical rain forests- low latitude forests near the equator -Coral Reefs -Deep Sea -Large tropical Lake *Those communities with the largest number of different species generally have only a few of each species or low species abundance

6. A. 3 Factors That Affect Species Diversity: 1) Latitude- Position on the latitudinal line of the earth. (terrestrial) “Latitudinal Species Diversity Gradient” REASONS: -resource availability -higher evolution rate -parasites keep down domination -speciation greater than extinction

7. “Latitudinal Species Diversity Gradient” 200 1,000 Species diversity 100 100 0 10 60 40 20 0 60 30 0 60 80˚N 90˚N 30˚S Latitude Latitude ANTS BIRDS

8. Local variations within terrestrial ecosystems Diversity tends to increase with… - increased solar radiation - increased precipitation - decreased elevation - strong seasonal variations

9. 2) Depth-How far down in an aquatic environment (aquatic) “Depth-species diversity gradient” REASONS: -Increased stability -Lack of nutrients in the mid-depths -Increased nutrients at bottom 3) Pollution- poisons (aquatic) REASON: -kills or impairs species

10. III. General Types of Species A. Native: - Normally live and thrive in an ecosystem B. Non-native: - Often called exotic, alien or invasive: - Migrate or Accidentally Introduced species; tend to crowd out native species

12. ACCIDENTAL STOWAWAYS

13. C. Indicator: - Serve as an early warning that an ecosystem is being damaged Ex: Birds, Trout, Frogs

14. D. Keystone: • Species that have a greater importance in the structure of the community • Play role in developing habitat and key role in food chain *Controversial among scientists

15. Species Interactions A) COMPETITION B) PREDATOR/PREY C) SYMBIOSIS

16. A) COMPETITION: 1.Intraspecific: -Competition between members of the same species -Territoriality: Patrol their area

17. 2. Interspecific: -Competition between 2 or more different species -Most common -Two types include… *Interference *Exploitation

18. Interference Competition: • One species limits another's access to a resource Exploitation Competition: • Competing species have equal access to the resources but differ in how fast they use it

19. High Relative population density Low 0 2 4 6 8 10 12 14 16 18 Days Each species grown alone COMPETITIVE EXCLUSION PRINCIPLE: The niches of 2 species cannot overlap completely or for an extended period of time Both species grown together

20. 3. ReducingCompetition Resource Partitioning Divide scarce resources so species use them at different times and/or places to live in same ecosystem to avoid excessive competition Ex: Lions/ Leopards, Owl/Hawk

21. B. PREDATION: (predator/prey) • Predator • Prey • Prey acquisition • Predator Avoidance

22. Quick escape Keen sense of smell and sight Protective shells Spines or thorns Camouflage Chemical warfare Warning coloration Mimicry: Imitate a dangerous species Behavior How do Prey Defend Themselves?

24. C. Symbiotic Species Interactions Symbiosis:Long lasting relationship where species live together 3 types of symbiotic relationships 1. Parasitism 2. Mutualism 3. Commensalism

25. 1. Parasitism • Species feeds on part of another organism • Host is usually harmed • Parasite is usually smaller than the host • Rarely kills the host • Endo/Ectoparasites Ex. Fleas, Ticks, Mosquitoes Ex. Tapeworms and humans

26. SHOW CLIP “NEVER UNDERESTIMATE THE BODY SNATCHERS” UNITED STREAMING: TAPEWORMS BODY SNATCHERS

27. 2. Mutualism • 2 species are in a relationship that is beneficial to both(win-win) • Providing Food + Protection

28. -Clownfish and sea anemones -Bacteria on roots of some plants -Bacteria in the digestive system -Protozoan's in termite guts -Birds catching a ride on rhinos -Roots and Rhizoids -Lichens (algae and bacteria) Examples of Mutualism

29. 3. Commensalism • Relationship that benefits one species but neither helps nor harms the other

31. V. Ecological Succession: A. SUCCESSION -Defined as a gradual change in species composition of a given area. 1. Primary Succession: -Succession that occurs where no ecosystem existed before. (bare rock, lava, etc. -Initiated by PIONEER SPECIES (moss and the like) and progresses to SUCCESSIONAL SPECIES (early, mid, and late)

32. Lichens and mosses Balsam fir, paper birch, and white spruce climax community Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Time Primary Succession- Exposed Rock

34. PRIMARY SUCCESSION – ALASKA, HAWAII

35. 2. Secondary Succession: -Succession that occurs where an ecosystem previously existed EX: Abandoned fields, polluted streams, strip mines, burned or cut forests

36. Mature oak-hickory forest Young pine forest Shrubs Perennial weeds and grasses Annual weeds Time Secondary Succession

37. SUCCESSION ON MT. MOUNT ST. HELEN

38. The Stages of Succession

39. Early Successional Species Rabbit Quail Ringneck pheasant Dove Bobolink Pocket gopher Midsuccessional Species Elk Moose Deer Ruffled grouse Snowshoe hare Bluebird Late Successional Species Turkey Martin Hammond’s Flycatcher Gray squirrel Wilderness Species Grizzly bear Wolf Caribou Bighorn sheep California condor Great horned owl Ecological succession Succession and Wildlife

40. B. Factors that affect the rate of succession One set of species makes an area suitable for species with different niche requirements • Facilitation • Inhibition Early species hinder the establishment and growth of other species Species are unaffected by members of another species from earlier stages of succession • Tolerance

41. C. Disturbances in Succession -Disturbance – a change in environmental conditions that disrupts an ecosystem or community. -Often categorized as CATASTROPHIC or GRADUAL (natural or human-caused.)

42. Catastrophic

43. Gradual

44. VI. Ecological Stability • Constant dynamic change in response to changing conditions 1. Inertia or Persistence: • Ability to resist being disturbed or altered 2. Constancy: • Ability to keep its #’s within the limits imposed by limited resources 3. Resilience: • Ability to bounce back after a disturbance

45. Precautionary Principle • When there is evidence that an activity harms the environment we should take precautionary measures • “Better Safe than Sorry”