2KEY PROPERTIES OF COMMUNITIES A communityIs an assemblage of species living close enough together for potential interaction..
3DiversityThe diversity of a community is the variety of different kinds of organisms that make up the communityThere are two main components:Species richness, the total number of different species in the communityRelative abundance of the different species..
4Prevalent Form of Vegetation The prevalent form of vegetation mainly depends on the terrestrial situationThe types and structural features of plants in a community largely determine the kinds of animals that live in the community..
5StabilityCommunity stability - ability to resist change and return to its original species combination after being disturbedDepends on both the type of community and the nature of disturbances..
6Trophic StructureThe trophic structure of a community concerns the feeding relationships among the various species making up the community..Figure 19.4
7INTERSPECIFIC INTERACTIONS IN COMMUNITIES Interspecific interactions are interactions between speciesCompetition between speciesPredationSymbiosis
8Competition Between Species Interspecific competitionMay occur when two or more species in a community rely on similar limiting resourcesMay limit population growth of the competing species..
9Competitive Exclusion Principle Russian ecologist G. F. Gause studied the effects of interspecific competition in two closely related species of protists..Separate culturesCombined culturesP. aureliaP. caudatumFigure 19.5
10From his research, Gause concluded that two species so similar that they compete for the same limiting resources cannot coexist in the same placeCompetitive Exclusion Principle..
11Testing the competitive exclusion principle.. High tideChthamalusBalanusOceanLow tideFigure 19.6
12The Ecological Niche A species’ ecological niche Is the sum total of a species’ use of the biotic and abiotic resources in its environmentIs the species’ ecological roleTwo species cannot coexist in a community if their niches are identical..
13Resource Partitioning Is the differentiation of niches that enables similar species to coexist in a communityThere are two possible outcomes of competition between species with identical nichesExtinction of one speciesEvolution of one species to use a different set of resources..
15Predation Is when organisms eat other organisms Identifies the predator as the consumer and the food species as the preyIncludes herbivory, the consumption of plants by animals..
16Predator Adaptations Most predators have acute senses Many predators Have adaptations such as claws, teeth, fangs, stingers, or poison to help catch and subdue preyAre fast and agile..
17Plant Defenses Against Herbivores Plants have various types of defenses against herbivoresChemical toxinsSpines and thorns..
18Animal Defenses Against Predators Animals can avoid being eatenBy using passive defenses such as hidingBy using active defenses such as escaping or defending themselves..
19Behavioral defenses include Alarm callsMobbing..Figure 19.8
20Distraction displaysDirect the attention of the predator away from a vulnerable prey to another prey that is more likely to escape..Figure 19.9
21Camouflage, or cryptic coloration Is a passive defense that makes a potential prey difficult to spot against its background..Figure 19.10
22Animals with chemical defenses are often brightly colored Some animals have mechanical or chemical defenses against predators..Animals with chemical defenses are often brightly coloredThis is a caution to predators called warning coloration..Figure 19.11
23MimicryIs a “copycat” adaptation in which one species mimics the appearance of anotherIs used by some species to gain protection..
24A palatable or harmless species mimics an unpalatable or harmful model.. Figure 19.12
25Two or more unpalatable species resemble each other.. Figure 19.13
26Predation and Species Diversity in Communities Predator-prey relationshipsCan actually preserve species diversity..
27The experiments of Robert Paine Removed a dominant predator from a communityProvided evidence of the phenomenon of predation..
28With Pisaster (control) Without PisasterFigure 19.14
29Paine’s experiments and others Led to the concept of keystone predatorsKeystone predatorsHelp maintain species diversity by preventing competitive exclusion of weaker competitors..
30Symbiotic Relationships Is an interspecific interaction in which one species, the symbiont, lives in or on another species, the hostParasitismMutualism
31Parasitism Parasitism Is a symbiotic relationship in which one organism benefits while the other is harmedThe parasite obtains its nutrients by living in or on its host organism..
32Mutualism Is a symbiosis that benefits both partners Many mutualistic relationships have evolved from predator-prey or host-parasite interactions..
33The Complexity of Community Networks The branching of interactions between species makes communities complex..WoundingDetection by plantRelease of volatile attractantsRecruitmentChemical in salivaFigure 19.17
34DISTURBANCE OF COMMUNITIES Are episodes that damage biological communities, at least temporarilyDestroy organisms and alter the availability of resourcesAffect all communities..
35Ecological Succession Is the process of community changePrimary successionSecondary succession..
36In primary successionA community arises in a virtually lifeless area with no soil..Retreating glacierBarren landscapeMoss & lichens
37Primary succession from barren soil to a complex community can take hundreds of years.. Shrubs & small treesLarger, intermediate speciesClimax community
38Secondary succession occurs where a disturbance has destroyed an existing community but left the soil intact..
39AN OVERVIEW OF ECOSYSTEM DYNAMICS An ecosystemIs a biological community and the abiotic factors with which the community interacts..
40Energy Flow Chemical cycling Is the passage of energy through the components of the ecosystemChemical cyclingIs the use and reuse of chemical elements within the ecosystem..
41Chemical cycling (C, N, etc.) EnergyFlows through an ecosystem when consumers feed on producersCannot be recycled within an ecosystem, but must flow through continuously..Chemical cycling (C, N, etc.)Chemical energyLight energyHeat energyFigure 19.20
42Energy flow and chemical cycling Depend on the transfer of substances in the feeding relationships, or trophic structure of an ecosystemTrophic levelsDivide the species of an ecosystem based on their main sources of nutritionTrophic relationshipsDetermine an ecosystem’s routes of energy flow and chemical cycling..
43Trophic Levels and Food Chains A food chainQuaternary consumersCarnivoreIs the sequence of food transfer from trophic level to trophic levelMay have many levels..CarnivoreTertiary consumersCarnivoreCarnivoreSecondary consumersCarnivoreCarnivorePrimary consumersHerbivoreZooplanktonProducersPlantPhytoplanktonFigure 19.21A terrestrial food chainA marine food chain
44Herbivores, which eat plants, algae, or autotrophic bacteria, are the primary consumers of an ecosystemAbove the primary consumers, the trophic levels are made up of carnivores, which eat the consumers from the levels belowSecondary consumers include many small mammals, such as rodents, and small fishes that eat zooplanktonTertiary consumers, such as snakes, eat mice and other secondary consumersQuaternary consumers include hawks and killer whales..
45Detritivores, or decomposers Derive their energy from the dead material left by all trophic levelsRecycle the nutrients locked in organisms..Figure 19.22
46Food Webs The feeding relationships in an ecosystem Are typically not as simple as in an unbranched food chainAre usually woven into complex food webs..
48ENERGY FLOW IN ECOSYSTEMS Food chains cannot be longer than 4 – 5 trophic levels.What limits food chains?
49Productivity and the Energy Budgets of Ecosystems BiomassIs the amount of organic material in an ecosystemAn ecosystem’s primary productivityIs the rate at which plants and other producers build biomass..
50Productivity of different ecosystems.. Percentage of Earth’s surface area(b) Average net primary productivity (g/m2/yr)(c) Percentage of Earth’s net primary productivityOpen oceanContinental shelfExtreme desert, rock, sand, iceDesert and semidesert scrubTropical rain forestSavannaCultivated landBoreal forest (taiga)Temperate grasslandWoodland and shrublandTundraTropical seasonal forestTemperate deciduous forestTemperate evergreen forestSwamp and marshLake and streamEstuaryAlgal beds and reedsUpwelling zones
51Energy PyramidsWhen energy flows as organic matter through the trophic levels of an ecosystem, much of it is lost at each link in a food chain..
52Plant material eaten by caterpillar 100 kilocalories (kcal)35 kcalCellular respiration50 kcalFeces15 kcalGrowthFigure 19.25
53An energy pyramidIs a diagram that represents the cumulative loss of energy from a food chain..
55CHEMICAL CYCLING IN ECOSYSTEMS Depend on a recycling of chemical elements..
56The General Scheme of Chemical Cycling Biogeochemical cyclesAre chemical cycles in an ecosystem that involve both biotic and abiotic components..
57Three key points to biogeochemical cycles Each circuit has an abiotic reservoirA portion of chemical cycling can rely completely on geological processesSome chemicals require processing before they are available as inorganic nutrients..
58Generalized scheme for biogeochemical cycles.. ConsumersProducersDetritivoresNutrients available to producersAbiotic reservoirGeologic processesGeneralized scheme for biogeochemical cycles..
59Examples of Biogeochemical Cycles A chemical’s specific route through an ecosystem varies with the particular element and the trophic structure of the ecosystem..
60Higher-level consumers The carbon cycleCO2 in atmosphereBurningWood and fossil fuelsCellular respirationHigher-level consumersDecompositionDetritivoresPhotosynthesisProducersPrimary consumersDetritusFigure 19.29a
61The nitrogen cycle Detritus Nitrates (NO3– ) Decomposition Denitrifying bacteriaAssimilation by plantsNitrogen (N2) in atmosphereAmino acids and proteins in plants and animalsDetritusDetritivoresNitrogen-fixing bacteria in root nodules of legumesDecompositionNitrogen fixationNitrogen-fixing bacteriain soilAmmonium (NH4+ )Nitrifying bacteriaNitrates (NO3– )
62Precipitated (solid) phosphates Phosphates in solution The phosphorous cycleUplifting of rockPhosphates in rockWeathering of rockPhosphatesin organic compoundsConsumersProducersRockPrecipitated (solid) phosphatesPhosphates in solutionin soil (inorganic)DetritusDetritivores in soilFigure 19.29c
63The water cycle Net movement of water vapor by wind (36) Solar heat Precipitation over the sea (283)Solar heatWater vapor over the seaOceansNet movement of water vapor by wind (36)Evaporation from the sea (319)Evaporation and transpiration (59)Water vapor over the landPrecipitation over the land (95)Surfacewater and groundwaterFlow of water from land to sea (36)Figure 19.29d
64BIOMESAre the major types of ecosystems that cover large geographic regions of the Earth..
65How Climate Affects Biome Distribution Because of its curvature, Earth receives an uneven distribution of solar energy.Low angle of incoming sunlightSunlight directly overheadAtmosphereFigure 19.30
66Cloud formation and rain Ascending moist air releases moisture The uneven heating causes rain and windHeated by the direct rays of the sun, air at the equator rises, then cools, forms clouds, and drops rain..Cloud formation and rainAscending moist air releases moistureDescending dry airTropicsTemperate zone
67Proximity to large bodies of water and the presence of landforms such as mountain ranges also affect climate..Wind directionPacific OceanEastCoast RangeCascade RangeFigure 19.32
68Terrestrial BiomesThe distribution of terrestrial biomes depends largely on climateIf the climate in two geographically separate areas is similar, the same type of biome may occur in them..
69Most biomes are named for major physical or climatic features and for their predominant vegetation.. Figure 19.33
78Freshwater Biomes Aquatic biomes Occupy the largest part of the biosphere..
79Lakes and PondsStanding bodies of water - range from small ponds to large lakes..Figure 19.35a
80The photic (photosynthetic) zone In lakes and large ponds the communities are distributed according to the depth of water and its distance from shore.The photic (photosynthetic) zoneIncludes the shallow water near shore and the upper stratum of water away from shoreIs named because light is available for photosynthesisThe aphotic zoneIs deeper, where light levels are too low to support photosynthesisThe benthic zoneIs the bottom of all aquatic biomes
81Rivers and Streams Are bodies of water flowing in one direction Support quite different communities of organisms than lakes and pondsFigure 19.35b
82Marshes, ponds, and other wetlands Are common in downstream areasFigure 19.35c
83Human activities have affected many streams and rivers Figure 19.36
84Marine Biomes Oceans Estuaries Cover about 75% of the planet’s surface Are areas where a freshwater stream or river merges with the oceanAre one of the most biologically productive environments on Earth“Nurseries of thesea”..
85Major Oceanic Zones Marine life is distributed according to Depth of the waterDegree of light penetrationDistance from shoreOpen water versus bottom..
86Oceanic zones Intertidal zone Continental shelf Pelagic zone Benthic zone (seafloor)Photic zoneAphotic zonePelagic zoneFigure 19.38
87The intertidal zone Is the area where land meets water Includes organisms adapted to attach to rocks or vegetation or to burrow..Figure 19.39
88The pelagic zone Is the open ocean Contains phytoplankton and zooplanktonPlankton are organisms that are pushed around because they are too small to resist the ocean currents..
89The benthic zone Is the ocean bottom or seafloor Temperature is constant 4o CMay include hydrothermal vent communities..Figure 19.40