1. Chapter 20 Community Ecology
20-1: Species Interactions

2. What’s a community?

3. 5 Comm. Interactions: PREDATION PARASITISM COMPETITION MUTUALISM
COMMENSALISM

4. Predation Predator eats prey Adaptations! Being a good predator:
Being a good escaper:
Teeth, venom, muscles, etc.
Camouflage
Mimicry
Plants—thorns, toxins, etc.

5. Mimicry: Avoiding Predation!
Batesian
Mullerian
B – harmless mimics a harmful
M-2 or more dangerous sp look similar (bees)

6. Competition
Interspecific
Intraspecific

7. Research in the Lab Gause, 1930s Yeast

8. Research in the Wild Connell, 1960s Barnacles Fundamental niche
Realized niche

9. Competitive Exclusion Principle
One species is excluded from a comm. b/c competition for same limited resource
No 2 species can occupy same niche at same time/place!
Resource partitioning
Resource part—similar species avoid competition by using a specific part of the resource

11. Niche Activity

12. SYMBIOSIS Parasitism Mutualism Commensalism
Symb – close, longterm relship btwn 2 organisms

13. PARASITISM

14. MUTUALISM

15. COMMENSALISM
The goby is essentially the 'guardian of the hole' as the shrimp has very limited visual abilities. Because of this, the shrimp, while outside the burrow, holds one antennae on the goby. If the goby sees a potential threat, it will give a slight tail flick. This vibration is picked up by the shrimp who consequently darts into the hole. If the danger approaches further, the goby will shoot into the hole through a quick C-bend of the body and enter the hole.

16. Concept map in groups

17. I’m checking today!

18. Chapter 20 Community Ecology
20-2: Patterns in Communities

19. Species Richness vs. Evenness
Richness-# sp in comm (count)
varies equator
trop habitats older (ice ages didn’t disturb), more stable climate
evenness- abundance of each sp (est pop size of each sp)

20. Latitude & Species Richness
Trend?
Hypotheses:

21. Area & Sp Richness
Trend?
Species-area effect
Habitat destruction...

22. Sp Interactions & Richness
Predation
keeps prey # in check
Paine, 1960s
Removed sea stars
Mussels previously coexisted w/several sp
Overabundance  outcompeting for space, etc
# sp from 20  <5 !

23. Richness & Community Stability
Tendency of comm to maintain ~constant conditions
Response to disturbance
More species  more interactions, spread out effects, lessen the blow

24. Brain Break…
p. 410—I’m checking it!

25. Ecological Succession
Primary
Secondary
Gradual, sequential regrowth of a community
1-didn’t support life previously; soil not present
2-did; disturbance, then sequential replacement of sp; soil present

26. Glacier Bay, AK

27. Pioneer Species
1st on the scene
Adapted to new conditions
Small, quick growing, reprod quickly

28. Climax Community
Stable end point
Remains constant long pd time
Too simple...
Disturbances often stop progression (grasslands...fires prevent forest)

29. p. 410—I’m checking it!

30. HW Tonight--Ch 20 Review p. 412, quiz tomorrow (THURS)