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Chapter 37

Chapter 37. Communities and Ecosystems. Dining In Community structure and function depend on the interactions among organisms Example: Apanteles glomeratus wasp, Pieris rapae butterfly, and other wasps

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Chapter 37

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  1. Chapter 37 Communities and Ecosystems

  2. Dining In • Community structure and function depend on the interactions among organisms • Example: Apanteles glomeratus wasp, Pieris rapae butterfly, and other wasps • Ecosystem structure and function depend on the interactions of the community with its abiotic environment

  3. STRUCTURAL FEATURES OF COMMUNITIES 37.1 A community includes all the organisms inhabiting a particular area • Biological community: an assemblage of all the populations of organisms living close enough together for potential interaction • Key characteristics of a community • Species diversity: variety of different kinds of organisms • Species richness • Relative abundance

  4. Dominant species • Response to disturbances • Trophic structure: feeding relationships among species

  5. 37.2 Competition may occur when a shared resource is limited • Interspecific competition may play a major role in structuring a community • Two species competing for the same limited resource • May inhibit growth of one or both species

  6. Competitive exclusion principle • Two species cannot coexist in a community if their niches are identical • Niche: species' total use of biotic and abiotic resources • Two possible results • Less competitive species will be driven to local extinction • Resource partitioning may evolve

  7. LE 37-2a

  8. LE 37-2b

  9. 37.3 Predation leads to diverse adaptations in both predator and prey • Predation is an interaction between species in which predator kills and eats prey • Adaptations of both tend to be refined through natural selection • Camouflage • Chemical defense Video: Seahorse Camouflage

  10. Batesian mimicry • Palatable species mimics an unpalatable model • Mullerian mimicry • Two unpalatable species mimic each other

  11. 37.4 Predation can maintain diversity in a community • Keystone species • Exerts strong control on community structure because of its ecological niche • Keystone predator • May maintain community diversity by reducing numbers of the strongest competitors • Removal can cause major changes in community dynamics

  12. 37.5 Herbivores and the plants they eat have various adaptations • Herbivores are animals that eat plants or algae • Have adaptations for locating and eating vegetation • Plants have evolved defenses against herbivores • Toxic chemicals • Physical defenses (spines, thorns)

  13. Some herbivore-plant interactions illustrate coevolution • Reciprocal evolutionary adaptations • Change in one species acts as a new selective force on another species

  14. LE 37-5 Eggs Sugar deposits

  15. 37.6 Symbiotic relationships help structure communities • Symbiotic relationship: interaction between two or more species that live in direct contact • Parasitism • Parasite lives on or near its host • Parasite obtains nourishment at the expense of host • Includes pathogens that may inflict lethal harm on host

  16. Commensalism • One species benefits without significantly affecting the other • Few absolute cases documented • Mutualism • Both partners benefit

  17. Video: Clownfish and Anemone

  18. 37.7 Disturbance is a prominent feature of most communities • Disturbances are characteristic of most biological communities • Events such as fire, storms, floods • Damage communities • Remove organisms from communities • Alter the availability of resources • Can have positive effects

  19. Ecological succession is a transition in community species composition following a major disturbance • Primary succession: gradual colonization of barren rocks • Secondary succession: occurs after a disturbance has destroyed a community but left the soil intact

  20. LE 37-7 Retreating glacier with moraine in the foreground Dryas stage Spruce starting to appear in the alder and cottonwood forest Spruce and hemlock forest

  21. TALKING ABOUT SCIENCE 37.8 Fire specialist Max Moritz discusses the role of fire in ecosystems • Dr. Max Moritz studies fire in chaparral ecosystems • Fire is a key abiotic factor in many ecosystems • Important in nutrient cycling • Creates conditions for regeneration of many plants • Dr. Moritz hopes to help people coexist with cycles of weather, vegetation, growth, and fire

  22. 37.9 Trophic structure is a key factor in community dynamics • Trophic structure: a pattern of feeding relationships consisting of several different levels • Food chain: sequence of food transfer up the trophic levels • Moves chemical nutrients and energy

  23. Producers • Autotrophs that support all other trophic levels • Plants on land • In water, mainly photosynthetic protists and cyanobacteria • Primary consumers • Herbivores that eat plants, algae, or phytoplankton

  24. Secondary, tertiary, and quaternary consumers • Eat consumers from the level below them • Detritivores (decomposers) • Animal scavengers, fungi, and prokaryotes • Derive energy from detritus produced at all trophic levels • Decomposition is essential for recycling nutrients in ecosystems Video: Shark Eating Seal

  25. LE 37-9 Trophic level Quaternary consumers Hawk Killer whale Tertiary consumers Snake Tuna Secondary consumers Herring Mouse Primary consumers Zooplankton Grasshopper Producers Plant Phytoplankton A terrestrial food chain An aquatic food chain

  26. 37.10 Food chains interconnect, forming food webs • A food web is a more realistic view of trophic structure • Consumers usually eat more than one type of food • Each food type is consumed by more than one type of consumer

  27. LE 37-10 Quaternary, tertiary, and secondary consumers Tertiary and secondary consumers Secondary and primary consumers Primary consumers Producers (plants)

  28. ECOSYSTEM STRUCTURE AND DYNAMICS 37.11 Ecosystem ecology emphasizes energy flow and chemical cycling • An ecosystem consists of all the organisms in a community and the abiotic factors with which they interact • Ecosystem dynamics involve two processes • Energy flow through the components of the ecosystem • Chemical cycling within the ecosystem

  29. LE 37-11 Chemical cycling Energy flow Chemical energy Light energy Heat energy Chemical elements

  30. 37.12 Primary production sets the energy budget for ecosystems • Primary production: amount of solar energy converted by producers to chemical energy in biomass • Biomass: amount of organic material in an ecosystem • Net primary production: amount of biomass produced minus amount used by producers in cellular respiration • Varies greatly among ecosystems

  31. LE 37-12 Open ocean Estuary Algal beds and coral reefs Desert and semidesert scrub Tundra Temperate grassland Cultivated land Boreal forest (taiga) Savanna Temperate deciduous forest Tropical rain forest 0 500 1,000 1,500 2,000 2,500 Average net primary productivity (g/m2/yr)

  32. 37.13 Energy supply limits the length of food chains • Only about 10% of the energy stored at each trophic level is available to the next level • Pyramid of production shows loss of energy from producers to higher trophic levels • Amount of energy available to top-level consumers is relatively small • Most food chains have only three to five levels

  33. LE 37-13 Tertiary consumers 10 kcal Secondary consumers 100 kcal Primary consumers 1,000 kcal Producers 10,000 kcal 1,000,000 kcal of sunlight

  34. CONNECTION 37.14 A production pyramid explains why meat is a luxury for humans • Human meat or fish eaters are tertiary or quaternary consumers • Humans eating grain have ten times more energy available than when they process the same amount of grain through meat • Using land to raise animals consumes more resources than using the land to cultivate crops

  35. LE 37-14 Trophic level Human meat-eaters Secondary consumers Primary consumers Human vegetarians Cattle Corn Corn Producers

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