Chapter 46: Community Structure and Biodiversity

1. Chapter 46: Community Structure and Biodiversity

2. Community • All the populations that live together in a habitat • Type of habitat shapes a community’s structure

3. Factors Shaping Community Structure • Climate and topography • Available foods and resources • Adaptations of species in community • Species interactions • Arrival and disappearance of species • Physical disturbances

4. Niche Sum of activities and relationships in which a species engages to secure and use resources necessary for survival and reproduction

5. Realized & Fundamental Niches • Fundamental niche • Theoretical niche occupied in the absence of any competing species • Realized niche • Niche a species actually occupies • Realized niche is some fraction of the fundamental niche

6. Species Interactions • Most interactions are neutral; have no effect on either species • Commensalism helps one species and has no effect on the other • Mutualism helps both species

7. Species Interactions • Interspecific competition has a negative effect on both species • Predation and parasitism both benefit one species at a cost to another

8. Symbiosis • Living together for at least some part of the life cycle • Commensalism, mutualism, and parasitism are forms of symbiosis

9. Mutualism • Both species benefit • Some are obligatory; partners depend upon each other • Yucca plants and yucca moth • Mycorrhizal fungi and plants

10. Yucca and Yucca Moth • Example of an obligatory mutualism • Each species of yucca is pollinated only by one species of moth • Moth larvae can grow only in that one species of yucca

11. Fig. 46-2b, p.822

12. Mycorrhizae • Obligatory mutualism between fungus and plant root • Fungus supplies mineral ions to root • Root supplies sugars to fungus

13. Sea Anemone and Fish Fig. 46-4, p.823

14. Competition • Interspecific - between species • Intraspecific - between members of the same species • Intraspecific competition is most intense

15. Forms of Competition • Competitors may have equal access to a resource; compete to exploit resource more effectively • One competitor may be able to control access to a resource, to exclude others

16. Interference Competition Least chipmunk is excluded from piñon pine habitat by the competitive behavior of yellow pine chipmunks Least Chipmunk Yellow Pine Chipmunk

17. Fig. 46-5a, p.824

18. Fig. 46-5b, p.824

19. Fig. 46-5c, p.824

20. Fig. 46-5d, p.824

21. Competitive Exclusion Principle When two species compete for identical resources, one will be more successful and will eventually eliminate the other

22. Gause’s Experiment Paramecium caudatum Species grown together Paramecium aurelia Figure 47.6 Page 825

23. Fig. 46-6a-c, p.825

24. Hairston’s Experiment • Two salamanders species overlap in parts of their ranges • Removed one species or the other in test plots • Control plots unaltered • 5 years later, salamander populations were growing in test plot

25. Fig. 46-7, p.825

26. Resource Partitioning • Apparent competitors may have slightly different niches • May use resources in a different way or time • Minimizes competition and allows coexistence Figure 47.8   Page 825

27. Fig. 46-8a, p.825

28. bristly foxtail Indian mallow smartweed Fig. 46-8b, p.825

29. Predation • Predators are animals that feed on other living organisms • Predators are free-living; they do not take up residence on their prey

30. Coevolution • Joint evolution of two or more species that exert selection pressure on each other as an outcome of close ecological interaction • As snail shells have thickened, claws of snail-eating crabs have become more massive

31. Predator-Prey Models • Type I model: Each individual predator will consume a constant number of prey individuals over time • Type II model: Consumption of prey by each predator increases, but not as fast as increases in prey density • Type III model: Predator response is lowest when prey density is lowest

32. Fig. 46-9a, p.826

33. Fig. 46-9c, p.826

34. Canadian Lynx and Snowshoe Hare • Show cyclic oscillations • Krebs studied populations for ten years • Fencing plots delayed cyclic declines but didn’t eliminate them • Aerial predators, plant abundance also involved • Three-level model

35. Fig. 46-10a, p.827

36. Fig. 46-10b, p.827

37. Fig. 46-10c, p.827

38. Prey Defenses • Camouflage • Warning coloration • Mimicry • Moment-of-truth defenses

39. Camouflage Fig. 46-11a, p.828

40. Camouflage Fig. 46-11b, p.828

41. Camouflage Fig. 46-11c, p.828

42. Mimicry Fig. 46-12a, p.829

43. Mimicry Fig. 46-12b, p.829

44. Predator Responses • Any adaptation that protects prey may select for predators that can overcome that adaptation • Prey adaptations include stealth, camouflage, and ways to avoid chemical repellents

45. Fig. 46-13a, p.829

46. Fig. 46-13b, p.829

47. Parasitism • Parasites drain nutrients from their hosts and live on or in their bodies • Natural selection favors parasites that do not kill their host too quickly

48. Fig. 46-14a, p.830

49. Fig. 46-14b, p.830

50. Kinds of Parasites • Microparasites • Macroparasites • Social parasites • Parasitoids