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Chapter 7 Community Ecology. Chapter Overview Questions  What determines the number of species in a community?  How can we classify species according.

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Presentation on theme: "Chapter 7 Community Ecology. Chapter Overview Questions  What determines the number of species in a community?  How can we classify species according."— Presentation transcript:

1 Chapter 7 Community Ecology

2 Chapter Overview Questions  What determines the number of species in a community?  How can we classify species according to their roles in a community?  How do species interact with one another?  How do communities respond to changes in environmental conditions?  Does high species biodiversity increase the stability and sustainability of a community?

3 Updates Online The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at to access InfoTrac articles.  InfoTrac: California's wild crusade. Virginia Morell. National Geographic, Feb 2006 v209 i2 p80(16).  InfoTrac: Traveling green. Carol Goodstein. Natural History, July-August 2006 v115 i6 p16(4).  InfoTrac: Too hot to trot. Charlie Furness. Geographical, May 2006 v78 i5 p51(7).  The Nature Conservancy: Jaguar Habitat and Center of Maya Civilization Protected in Historic Land Deal  National Geographic News: Conservationists Name Nine New "Biodiversity Hotspots"

4 Core Case Study: Why Should We Care about the American Alligator?  Hunters wiped out population to the point of near extinction.  Alligators have important ecological role. Figure 7-1

5 Core Case Study: Why Should We Care about the American Alligator?  Dig deep depressions (gator holes). Hold water during dry spells, serve as refuges for aquatic life. Hold water during dry spells, serve as refuges for aquatic life.  Build nesting mounds. provide nesting and feeding sites for birds. provide nesting and feeding sites for birds. Keeps areas of open water free of vegetation. Keeps areas of open water free of vegetation.  Alligators are a keystone species: Help maintain the structure and function of the communities where it is found. Help maintain the structure and function of the communities where it is found.

6 Endangered Species  1967 – American Alligator listed as endangered  By 1977 – reduced listing to threatened  Now there are farms that provide alligator meat and skin  There are invasive species that threaten the alligators: breeding populations of burmese pythons in Florida

7 COMMUNITY STRUCTURE AND SPECIES DIVERSITY  Biological communities differ in their structure and physical appearance. Figure 7-2

8 Fig. 7-2, p. 144 Short-grass prairie Desert scrub Tall-grass prairie Thorn scrub Thorn forest Deciduous forest Coniferous forest Tropical rain forest

9 Species Diversity and Niche Structure: Different Species Playing Different Roles  Biological communities differ in the types and numbers of species they contain and the ecological roles those species play. Species diversity/ species richness Species diversity/ species richness the number of different species it containsthe number of different species it contains species evenness species evenness combined with the abundance of individuals within each of those speciescombined with the abundance of individuals within each of those species Do you have equal numbers of different species? Do you have equal numbers of different species?

10 The Edges  Community structure varies around the edges How? How? Might be sunnier, warmer, drier than forest interior Might be sunnier, warmer, drier than forest interior  Increasing edges with habitat fragmentation increases stress on organisms How? How? Species more vulnerable to predators and fire Species more vulnerable to predators and fire Can create barriers to colonizing new areas, finding mates and food Can create barriers to colonizing new areas, finding mates and food

11 Species Diversity and Niche Structure  Niche structure: how many potential ecological niches occur? how many potential ecological niches occur? how they resemble or differ? how they resemble or differ? how the species occupying different niches interact? how the species occupying different niches interact?  Geographic location: species diversity is highest in the tropics and declines as we move from the equator toward the poles. species diversity is highest in the tropics and declines as we move from the equator toward the poles.

12 TROPIC  Consistent daily climate and reliable food sources results in specialists with narrow niches versus generalists  Species in higher latitudes with variable weather have adaptations that allow them to survive in a greater range of environments

13 TYPES OF SPECIES  Native, nonnative, indicator, keystone, and foundation species play different ecological roles in communities. Native: Native: those that normally live and thrive in a particular community.those that normally live and thrive in a particular community. Nonnative species: Nonnative species: those that migrate, deliberately or accidentally introduced into a community.those that migrate, deliberately or accidentally introduced into a community. Also known as invasiveAlso known as invasive

14 Purposely introducing nonnatives  1957 the African bee was introduced to increase the productivity of honey bees  This introduction created “The killler bees”  They have migrated North but are limited by cold weather.  Theses bees are overly aggressive compared with commercial honey bees

15 CANE TOAD  We will watch a video that discusses the affects of the CANE TOAD introduced in Australia

16 Case Study: Species Diversity on Islands  MacArthur and Wilson proposed the species equilibrium model or theory of island biogeography in the 1960’s.  Model projects that at some point the rates of immigration and extinction should reach an equilibrium based on: Island size Island size Distance to nearest mainland Distance to nearest mainland

17 Possible Author for Book  E. O. Wilson  Main works  The Theory of Island Biogeography, 1967, Princeton University Press (2001 reprint), ISBN , with Robert H. MacArthur The Theory of Island BiogeographyISBN The Theory of Island BiogeographyISBN  The Insect Societies, 1971, Harvard University Press, ISBN The Insect SocietiesHarvard University PressISBN The Insect SocietiesHarvard University PressISBN  Sociobiology: The New Synthesis 1975, Harvard University Press, (Twenty-fifth Anniversary Edition, 2000 ISBN ) Sociobiology: The New SynthesisHarvard University PressISBN Sociobiology: The New SynthesisHarvard University PressISBN  On Human Nature, 1979, Harvard University Press, ISBN On Human NatureHarvard University PressISBN On Human NatureHarvard University PressISBN  Genes, Mind and Culture: The coevolutionary process, 1981, Harvard University Press, ISBN Genes, Mind and Culture: The coevolutionary processHarvard University PressISBN Genes, Mind and Culture: The coevolutionary processHarvard University PressISBN  Promethean fire: reflections on the origin of mind, 1983, Harvard University Press, ISBN Promethean fire: reflections on the origin of mindHarvard University PressISBN Promethean fire: reflections on the origin of mindHarvard University PressISBN  Biophilia, 1984, Harvard University Press, ISBN BiophiliaHarvard University PressISBN BiophiliaHarvard University PressISBN

18  Success and Dominance in Ecosystems: The Case of the Social Insects, 1990, Inter-Research, ISSN Success and Dominance in Ecosystems: The Case of the Social InsectsInter-Research Success and Dominance in Ecosystems: The Case of the Social InsectsInter-Research  The Ants, 1990, Harvard University Press, ISBN , Winner of the Pulitzer Prize, with Bert Hölldobler The AntsHarvard University PressISBN Pulitzer PrizeBert Hölldobler The AntsHarvard University PressISBN Pulitzer PrizeBert Hölldobler  The Diversity of Life, 1992, Harvard University Press, ISBN , The Diversity of Life: Special Edition, ISBN The Diversity of LifeHarvard University PressISBN The Diversity of Life: Special EditionISBN The Diversity of LifeHarvard University PressISBN The Diversity of Life: Special EditionISBN  The Biophilia Hypothesis, 1993, Shearwater Books, ISBN , with Stephen R. Kellert The Biophilia HypothesisISBN The Biophilia HypothesisISBN  Journey to the Ants: A Story of Scientific Exploration, 1994, Harvard University Press, ISBN , with Bert Hölldobler Journey to the Ants: A Story of Scientific ExplorationHarvard University PressISBN Bert Hölldobler Journey to the Ants: A Story of Scientific ExplorationHarvard University PressISBN Bert Hölldobler  Naturalist, 1994, Shearwater Books, ISBN NaturalistISBN NaturalistISBN  In Search of Nature, 1996, Shearwater Books, ISBN , with Laura Simonds Southworth In Search of NatureISBN In Search of NatureISBN  Consilience: The Unity of Knowledge, 1998, Knopf, ISBN Consilience: The Unity of KnowledgeISBN Consilience: The Unity of KnowledgeISBN  The Future of Life, 2002, Knopf, ISBN The Future of LifeISBN The Future of LifeISBN  Pheidole in the New World: A Dominant, Hyperdiverse Ant Genus, 2003, Harvard University Press, ISBN Pheidole in the New World: A Dominant, Hyperdiverse Ant GenusHarvard University Press ISBN Pheidole in the New World: A Dominant, Hyperdiverse Ant GenusHarvard University Press ISBN  From So Simple a Beginning: Darwin's Four Great Books. 2005, W. W. Norton.  The Creation: An Appeal to Save Life on Earth, September 2006, W. W. Norton & Company, Inc. ISBN ISBN ISBN  Nature Revealed: Selected Writings , Johns Hopkins University Press, Baltimore. ISBN ISBN ISBN  The Superorganism: The Beauty, Elegance, and Strangeness of Insect Societies, 2009, W.W. Norton & Company, Inc. ISBN , with Bert Hölldobler ISBN Bert HölldoblerISBN Bert Hölldobler

19 Indicator Species: Biological Smoke Alarms Species that serve as early warnings of damage to a community or an ecosystem. Presence or absence of trout species because they are sensitive to temperature and oxygen levels. Presence or absence of trout species because they are sensitive to temperature and oxygen levels. Birds are affected quickly by change Birds are affected quickly by change Butterflies are associated with certain plants Butterflies are associated with certain plants Coal miners used to use canaries Coal miners used to use canaries If they stopped singing then its time to get out!!!If they stopped singing then its time to get out!!!

20 Keystone Species: Major Players  Keystone species help determine the types and numbers of other species in a community thereby helping to sustain it. How were Yellowstone wolves a keystone species? How were Yellowstone wolves a keystone species? Figures 7-4 and 7-5

21 Case Study: Why are Amphibians Vanishing?  Frogs serve as indicator species because different parts of their life cycles can be easily disturbed. Figure 7-3

22 Fig. 7-3, p. 147 Young frog Adult frog (3 years) Sperm Sexual Reproduction Eggs Fertilized egg development Organ formation Egg hatches Tadpole Tadpole develops into frog

23 Case Study: Why are Amphibians Vanishing?  Frogs sensitive at various stage of life Eggs absorb UV radiation or pollution Eggs absorb UV radiation or pollution Tadpoles live in water and eat plants Tadpoles live in water and eat plants As adults they eat insects (pesticide exposure) As adults they eat insects (pesticide exposure)  Frogs have thin permeable skin Easily absorb pollutants from water, air, soil Easily absorb pollutants from water, air, soil As of % of populations threatened As of % of populations threatened 43% of populations declining 43% of populations declining

24 Case Study: Why are Amphibians Vanishing?  See answers on next slide

25 FROGS: No single cause has been indentified 1. Habitat loss and fragmentation Draining and filling wetlands, deforestation, development Draining and filling wetlands, deforestation, development 2. Prolonged drought: kills tadpoles 3. Pollution Pesticides = sensitivity to bacterial, viral and fungal diseases and cause sexual abnormalities Pesticides = sensitivity to bacterial, viral and fungal diseases and cause sexual abnormalities 4. Increases in ultraviolet radiation from ozone layer destruction Harms embryos of amphibians in shallow ponds Harms embryos of amphibians in shallow ponds

26 Frogs continued 5. Parasistes 6. Viral and Fungal diseases Chytrid fungus attacks the skin Chytrid fungus attacks the skin 7. Climate Change: 5. Evaporated water increases cloud cover, lowers daytime temps and warms night = chytrid fungi 8. Overhunting (Frog leg delicacy in Asia and France) 9. Natural immigration or deliberate introduction of nonnative predators + competitors

27 Why should we care if frogs die?  They signal degradation of habitat  They eat insects  They are genetic storehouse of pharmaceutical products waiting to be discovered Painkillers, antibiotics, burns, heart disease, etc Painkillers, antibiotics, burns, heart disease, etc  They might not need us, but we need them

28 Video: Frogs Galore  From ABC News, Biology in the Headlines, 2005 DVD. PLAY VIDEO

29 Foundation Species: Other Major Players  Expansion of keystone species category.  Foundation species can create and enhance habitats that can benefit other species in a community. Elephants push over, break, or uproot trees, creating forest openings promoting grass growth for other species to utilize. Elephants push over, break, or uproot trees, creating forest openings promoting grass growth for other species to utilize. Bats and birds regenerate deforested areas (how?) Bats and birds regenerate deforested areas (how?) Beavers create wetlands Beavers create wetlands

30 How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.  Do we have an ethical obligation to protect shark species from premature extinction and treat them humanely? a. No. It's impractical to force international laws on individual fishermen that are simply trying to feed their families with the fishing techniques that they have. a. No. It's impractical to force international laws on individual fishermen that are simply trying to feed their families with the fishing techniques that they have. b. Yes. Sharks are an important part of marine ecosystems. They must be protected and, like all animals, they should be humanely treated. b. Yes. Sharks are an important part of marine ecosystems. They must be protected and, like all animals, they should be humanely treated.

31 Sharks  Whale shark dorsal fin can = $10,000  Bowl of soup can = $100  Yet fins found to be high in MERCURY  Sharks killed because we fear them, yet only 7 people per year on average die from sharks  SHARKS are our key to cancer.  Sharks rarely get cancer and have effective immune systems  They grow slow, mature late = SENSITIVE TO OVERFISHING SENSITIVE TO OVERFISHING

32 SPECIES INTERACTIONS: COMPETITION AND PREDATION  Species can interact through competition, predation, parasitism, mutualism, and commensalism.  Some species evolve adaptations that allow them to reduce or avoid competition for resources with other species (resource partitioning).

33 Resource Partitioning  Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion of the spruce tree and by consuming somewhat different insect species. Figure 7-7

34 Niche Specialization  Niches become separated to avoid competition for resources. Figure 7-6

35 Fig. 7-6, p. 150 Species 2 Species 1 Number of individuals Species 2 Species 1 Resource use Region of niche overlap

36 Examples  The lion eats larger animals and leopards eat the smaller animals when both exist in the same habitat.  Hawks hunt by day and Owls hunt the same prey by night.

37 SPECIES INTERACTIONS: COMPETITION AND PREDATION  Species called predators feed on other species called prey.  Organisms use their senses their senses to locate objects and prey and to attract pollinators and mates.  Some predators are fast enough to catch their prey, some hide and lie in wait, and some inject chemicals to paralyze their prey.

38 PREDATION  Some prey escape their predators or have outer protection, some are camouflaged, and some use chemicals to repel predators. Figure 7-8

39 Fig. 7-8a, p. 153 (a) Span worm Camouflage

40 Fig. 7-8b, p. 153 (b) Wandering leaf insect Camouflage

41 Fig. 7-8c, p. 153 (c) Bombardier beetle Chemical Warfare

42 Fig. 7-8d, p. 153 (d) Foul-tasting monarch butterfly Chemical Warfare Warning coloration

43 Fig. 7-8e, p. 153 (e) Poison dart frog Chemical Warfare Warning coloration

44 Fig. 7-8f, p. 153 (f) Viceroy butterfly mimics monarch butterfly mimicry

45 Fig. 7-8g, p. 153 (g) Hind wings of Io moth resemble eyes of a much larger animal.

46 Fig. 7-8h, p. 153 (h) When touched, snake caterpillar changes shape to look like head of snake. Deceptive Behavior

47 SPECIES INTERACTIONS: PARASITISM, MUTUALISM, AND COMMENSALIM  Parasitism occurs when one species feeds on part of another organism.  In mutualism, two species interact in a way that benefits both.  Commensalism is an interaction that benefits one species but has little, if any, effect on the other species.

48 Parasites: Sponging Off of Others  Although parasites can harm their hosts, they can promote community biodiversity. Some parasites live in host (micororganisms, tapeworms). Some parasites live in host (micororganisms, tapeworms). Some parasites live outside host (fleas, ticks, mistletoe plants, sea lampreys). Some parasites live outside host (fleas, ticks, mistletoe plants, sea lampreys). Some have little contact with host (dump-nesting birds like cowbirds, some duck species) Some have little contact with host (dump-nesting birds like cowbirds, some duck species)

49 Mutualism: Win-Win Relationship  Two species can interact in ways that benefit both of them. Figure 7-9

50 Fig. 7-9a, p. 154 (a) Oxpeckers and black rhinoceros

51 Fig. 7-9b, p. 154 (b) Clownfish and sea anemone

52 Fig. 7-9c, p. 154 (c) Mycorrhizal fungi on juniper seedlings in normal soil

53 Fig. 7-9d, p. 154 (d) Lack of mycorrhizal fungi on juniper seedlings in sterilized soil

54 Mutualism The microorganisms in our digestive tract and other guts help digest food and benefit from a sheltered habitat with a consistent food supply Without termites there would not be a decay of cellulose. Termites have bacteria and protozoan that help them breakdown cellulose (tough carbohydrates in plants)

55 Commensalism: Using without Harming  Some species interact in a way that helps one species but has little or no effect on the other. Figure 7-10

56 EPIPHYTES  Some orchids grow in the branches of other trees.  They appear to not harm their host tree.

57 ECOLOGICAL SUCCESSION: COMMUNITIES IN TRANSITION  New environmental conditions allow one group of species in a community to replace other groups.  Ecological succession: the gradual change in species composition of a given area Primary succession: the gradual establishment of biotic communities in lifeless areas where there is no soil or sediment. Primary succession: the gradual establishment of biotic communities in lifeless areas where there is no soil or sediment. Secondary succession: series of communities develop in places containing soil or sediment. Secondary succession: series of communities develop in places containing soil or sediment.

58 Primary Succession: Starting from Scratch  Primary succession begins with an essentially lifeless are where there is no soil in a terrestrial ecosystem Figure 7-11

59 Fig. 7-11, p. 156 Exposed rocks Lichens and mosses Small herbs and shrubs Heath mat Jack pine, black spruce, and aspen Balsam fir, paper birch, and white spruce forest community Time Started on new islands, melted glaciers, after volcanic eruptions Succession is dependent on climate

60 Secondary Succession: Starting Over with Some Help  Secondary succession begins in an area where the natural community has been disturbed. Figure 7-12

61 Fig. 7-12, p. 157 Time Annual weeds Perennial weeds and grasses Shrubs and pine seedlings Young pine forest with developing understory of oak and hickory trees Mature oak-hickory forest

62 Can We Predict the Path of Succession, and is Nature in Balance?  The course of succession cannot be precisely predicted.  Previously thought that a stable climax community will always be achieved.  Succession involves species competing for enough light, nutrients and space which will influence it’s trajectory.

63 ECOLOGICAL STABILITY AND SUSTAINABILITY  Living systems maintain some degree of stability through constant change in response to environmental conditions through:

64 Inertia (persistence): Inertia (persistence): the ability of a living system to resist being disturbed or altered.the ability of a living system to resist being disturbed or altered. Constancy: Constancy: the ability of a living system to keep its numbers within the limits imposed by available resources.the ability of a living system to keep its numbers within the limits imposed by available resources. Resilience: Resilience: the ability of a living system to bounce back and repair damage after (a not too drastic) disturbance.the ability of a living system to bounce back and repair damage after (a not too drastic) disturbance.

65 ECOLOGICAL STABILITY AND SUSTAINABILITY  Having many different species appears to increase the sustainability of many communities.  Human activities are disrupting ecosystem services that support and sustain all life and all economies.

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