Community Structure & Biodiversity

1. Community Structure & 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. 46-3a, p.823

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

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

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

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

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

20. 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

21. P. glutinosis P. jordani Fig. 46-7, p.825

22. 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

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

24. 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

25. 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

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

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

28. Variation in Cycles • An association in predator and prey abundance does not always indicate a cause and effect relationship • Variations in food supply and additional predators may also influence changes in prey abundance

29. 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

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

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

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

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

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

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

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

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

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

39. Mimicry Fig. 46-12c, p.829

40. Mimicry Fig. 46-12d, p.829

41. 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

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

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

44. Fig. 46-13d, p.829

45. 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

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

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

48. Fungus and Frogs • Amphibians are disappearing even in undisturbed tropical forests • Infection by a parasitic chytrid is one of the causes of the recent mass deaths

49. Parasitic Plants • Holoparasites • Nonphotosynthetic; withdraw nutrients and water from young roots • Hemiparasites • Capable of photosynthesis, but withdraw nutrients and water from host

50. Devil’s Hair Fig. 46-15a, p.830