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Community and Population Ecology

Community and Population Ecology. Chapter 6. Core Case Study: American Alligator. Highly adaptable Only natural predator is humans 1967 – endangered species list Successful environmental comeback Keystone species. American Alligator. Fig. 6-1, p. 105.

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Community and Population Ecology

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  1. Community and Population Ecology Chapter 6

  2. Core Case Study: American Alligator • Highly adaptable • Only natural predator is humans • 1967 – endangered species list • Successful environmental comeback • Keystone species

  3. American Alligator Fig. 6-1, p. 105

  4. 6-1 How Does Species Diversity Affect the Sustainability of a Community? • Concept 6-1 Species diversity is a major component of biodiversity and tends to increase the sustainability of communities and ecosystems.

  5. Species Diversity • Species richness combined with species evenness • Niche structure • Varies with geographic location • Species richness declines towards poles

  6. Sustainability and Environmental Change • Inertia or persistence • Constancy • Resilience

  7. Science Focus: Community Sustainability • No certain definition of sustainability • Do communities need high inertia and high resilience? • Communities may have one but not the other • Equilibrium is rare

  8. Richness and Sustainability • Hypotheses • Does a community with high species richness have greater sustainability and productivity? • Is a species-rich community better able to recover from a disturbance? • Research suggests “yes” to both

  9. 6-2 What Roles Do Species Play in a Community? • Concept 6-2 Based on certain ecological roles they play in communities, species are described as native, nonnative, indicator, keystone, or foundation species.

  10. Ecological Niche • Species occupy unique niches • Native species • Nonnative species • Spread in new, suitable niches

  11. Indicator Species • Early warning system • Birds • Butterflies • Amphibians

  12. Case Study: Why Are Amphibians Vanishing? (1) • Habitat loss and fragmentation • Prolonged drought • Pollution • Ultraviolet radiation • Parasites

  13. Case Study: Why Are Amphibians Vanishing? (2) • Viral and fungal diseases • Climate change • Overhunting • Nonnative predators and competition • Why we should care

  14. Life Cycle of Typical Frog

  15. Adult frog (3 years) Young frog Tadpole develops into frog Sperm Sexual reproduction Tadpole Eggs Fertilized egg development Egg hatches Organ formation Fig. 6-2, p. 109

  16. Keystone Species • Significant role in their food web • Elimination may alter structure, function of community • Pollinators • Top predators

  17. Keystone Species: Dung Beetle Fig. 6-3, p. 110

  18. Foundation Species • Create habitats and ecosystems • Beavers • Elephants • Seed dispersers

  19. Science Focus: Why Should WeProtect Sharks? • Remove injured, sick animals • Many are gentle giants • Provide potential insight into cures for human diseases • Keystone species

  20. 6-3 How Do Species Interact? • Concept 6-3A Five basic species interactions – competition, predation, parasitism, mutualism, and commensalism – affect the resource use and population sizes of the species in a community. • Concept 6-3B Some species develop adaptations that allow them to reduce or avoid competition for resources with other species.

  21. Interspecific Competition • No two species can share vital limited resources for long • Resolved by: • Migration • Shift in feeding habits or behavior • Population drop • Extinction • Intense competition leads to resource partitioning

  22. Resource Partitioning in Warblers

  23. Blakburnian Warbler Black-throated Green Warbler Cape May Warbler Bay-breasted Warbler Yellow-rumped Warbler Fig. 6-4, p. 112

  24. Predation • Predator-prey relationship • Predators and prey both benefit – individual vs. population • Predator strategies • Prey strategies

  25. Predator Avoidance

  26. Fig. 6-5ab, p. 113

  27. (a) Span worm (b) Wandering leaf insect Fig. 6-5ab, p. 113

  28. Fig. 6-5cd, p. 113

  29. (c) Bombardier beetle (d) Foul-tasting monarch butterfly Fig. 6-5cd, p. 113

  30. Fig. 6-5ef, p. 113

  31. (e) Poison dart frog (f) Viceroy butterfly mimics monarch butterfly Fig. 6-5ef, p. 113

  32. Fig. 6-5gh, p. 113

  33. (h) When touched, snake caterpillar changes shape to look like head of snake. (g) Hind wings of Io moth resemble eyes of a much larger animal. Fig. 6-5gh, p. 113

  34. Parasitism • Live in or on the host • Parasite benefits, host harmed • Parasites promote biodiversity

  35. Mutualism • Everybody benefit by unintentional exploitation • Nutrition and protection • Gut inhabitant mutualism

  36. Mutualism in Action

  37. (a) Oxpeckers and black rhinoceros (b) Clownfish and sea anemone (c) Mycorrhizal fungi on juniper seedlings in normal soil (d) Lack of mycorrhizal fungi on juniper seedlings in sterilized soil Fig. 6-6, p. 114

  38. Commensalism • Benefits one with little impact on other

  39. 6-4 How Do Communities Respond to Changing Environmental Conditions? • Concept 6-4A The structure and species composition of communities change in response to changing environmental conditions through a process called ecological succession. • Concept 6-4B According to the precautionary principle, we should take measures to prevent or reduce harm to human health and natural systems even if some possible cause-and-effect relationships have not been fully established scientifically.

  40. Ecological Succession • Primary succession • Secondary succession • Disturbances create new conditions • Intermediate disturbance hypothesis

  41. Primary Ecological Succession

  42. Balsam fir, paper birch, and white spruce forest community Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Lichens and mosses Exposed rocks Time Fig. 6-8, p. 115

  43. Lichens and mosses Exposed rocks Balsam fir, paper birch, and white spruce forest community Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Time Stepped Art Fig. 6-8, p. 115

  44. Secondary Ecological Succession

  45. Mature oak and hickory forest Young pine forest with developing understory of oak and hickory trees Shrubs and small pine seedlings Perennial weeds and grasses Annual weeds Time Fig. 6-9, p. 116

  46. Mature oak and hickory forest Young pine forest with developing understory of oak and hickory trees Shrubs and small pine seedlings Perennial weeds and grasses Annual weeds Time Stepped Art Fig. 6-9, p. 116

  47. Succession’s Unpredictable Path • Successional path not always predictable toward climax community • Communities are ever-changing mosaics of different stages of succession • Continual change, not permanent equilibrium

  48. Precautionary Principle • Lack of predictable succession and equilibrium should not prevent conservation • Ecological degradation should be avoided • Better safe than sorry

  49. 6-5 What Limits the Growth of Populations? • Concept 6-5 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

  50. Population Distribution • Clumping – most populations • Uniform dispersion • Random dispersion

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