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Chapter 53

Chapter 53. Community Ecology. Community- a group of populations of various species living close enough for potential interaction. How many interactions between species are occurring in this scene?. Competition.

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Chapter 53

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  1. Chapter 53 Community Ecology

  2. Community- a group of populations of various species living close enough for potential interaction How many interactions between species are occurring in this scene?

  3. Competition • Competitive exclusion- strong competition can lead to the elimination of a competing species • Competitive exclusion principle- two species competing for the same limiting resources cannot coexist in the same place

  4. Ecological Niches • Ecological niche- the total of a species’ use of biotic and abiotic resources • Resource partitioning- differentiation of ecological niches, enabling similar species to coexist in a community

  5. A. distichus perches on fence posts and other sunny surfaces. A. insolitus usually perches on shady branches. Resource partitioning among Dominican Republic lizards A. ricordii A. insolitus A. aliniger A. christophei A. distichus A. cybotes A. etheridgei

  6. Predation • Cryptic coloration (camouflage)- makes prey difficult to spot Cryptic coloration Canyon tree frog

  7. Aposematic coloration- animals with effective chemical defense often exhibit bright warning coloration (b) Poison dart frog

  8. Batesian mimicry- a harmless species mimics an unpalatable or harmful model Hawkmoth larva Green parrot snake

  9. Müllerian mimicry- two or more unpalatable species resemble each other Cuckoo bee Yellow jacket

  10. Symbiosis • Parasitism- the parasite derives nourishment from a host which is harmed in the process • Mutualism- an interaction that benefits both species • Commensalism - one species benefits and the other is apparently unaffected

  11. Species Diversity • Species Diversity of a community is the variety of organisms that make up the community • Species richness- the total number of different species in the community • Relative abundance- the proportion each species represents of the total individuals in the community

  12. A B C D Community 1 Community 2 A: 80% B: 5% C: 5% D: 10% A: 25% B: 25% C: 25% D: 25%

  13. Trophic Structure Trophic Structure- the feeding relationships between organisms in a community • Food chains link trophic levels from producers to top carnivores • Food web- a branching food chain with complex trophic interactions

  14. Humans Quaternary consumers Carnivore Smaller toothed whales Carnivore Sperm whales Baleen whales Tertiary consumers Carnivore Carnivore Elephant seals Leopard seals Crab-eater seals Secondary consumers Carnivore Carnivore Squids Fishes Birds Primary consumers Carnivorous plankton Herbivore Zooplankton Euphausids (krill) Copepods Primary producers Phyto- plankton Plant Phytoplankton A terrestrial food chain A marine food chain

  15. Each food chain in a food web is usually only a few links long • Energetic hypothesis- length is limited by inefficient energy transfer • Dynamic stability hypothesis- long food chains are less stable than short ones

  16. Species with a Large Impact • Dominant species- those that are most abundant or have the highest biomass • Invasive species -introduced to a new environment, often lack predators or disease • Keystone species- exert strong control on a community by their ecological roles, or niches

  17. Foundation Species (Ecosystem “Engineers”) • Foundation Species (Ecosystem “Engineers”)- cause physical changes in the environment that affect community structure

  18. Ecological Succession Ecological succession-the sequence of community and ecosystem changes after a disturbance • Primary succession occurs where no soil exists when succession begins • Secondary succession begins in an area where soil remains after a disturbance

  19. Glacial retreat and primary succession at Glacier Bay, Alaska 1941 1907 2 Dryas stage Pioneer stage, with fireweed dominant 1 0 5 10 15 Kilometers 1860 Glacier Bay Alaska 1760 4 Spruce stage 3 Alder stage

  20. Fig. 54-22a Pioneer stage, with fireweed dominant 1

  21. Dryas stage 2

  22. Alder stage 3

  23. Spruce stage 4

  24. 60 50 40 Soil nitrogen (g/m2) 30 20 10 0 Pioneer Dryas Alder Spruce Successional stage

  25. Area Effects • Species-area curve- all other factors being equal, a larger geographic area has more species

  26. Species-area curve for North American breeding birds 1,000 100 Number of species 10 1 0.1 1 10 100 103 104 105 106 107 108 109 1010 Area (hectares)

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