Presentation on theme: "Chapter 41 Community Ecology (Sections )"— Presentation transcript:
1 Chapter 41 Community Ecology (Sections 41.1 - 41.5)
2 41.1 Fighting Foreign Fire Ants Red imported fire ants, Solenopsis invicta, have a venomous sting, disrupt native wildlife communities, and are not controlled by pesticidesBiological control involves phorid flies, specialized parasites (parasitoids) that kill their host by laying an egg in the ant’s tissues – the larvae eats its way through the fire ant and undergoes metamorphosis in its headcommunityAll species that live in a particular region
3 Phorid Fly and Fire AntPhorid flies insert a fertilized egg into an ant’s thoraxParasitized ant that lost its head after a developing fly larva moved into itFigure 41.1 Red imported fire ants and their foes. Opposite, nest mounds of fire ants in a Texas pasture. A Phorid fly. This fly uses nia and as far north as Kansas and Delaware. the hooked extension on its abdomen to insert a fertilized egg into an ant’s thorax. B Parasitized ant that lost its head after a developing the fly larva moved into it. The larva will undergo metamor phosis to an adult inside the detached head.
4 41.2 Community StructureThe type of place where a species normally lives is its habitat, and all species living in a habitat constitute a communityCommunities often are nested one inside anotherhabitatType of environment in which a species typically lives
5 Species Diversity Communities differ in their species diversity Species diversity has two components:Species richness (number of species)Species evenness (relative abundance of each species)Community structure is dynamicSpecies richness and evenness change over time
6 Factors Affecting Community Structure Community structure can change:As the community forms and agesAs a result of natural or human-induced disturbancesWith changes in physical factors such as climate and resource availabilityDue to various types of species interactions
7 Species InteractionsSpecies interactions can be mutually beneficial, mutually harmful, or benefit one species while harming the otherExample: Commensal ferns attached to the trunk of a tree; the fern benefits from the light, and the tree is unaffectedcommensalismSpecies interaction that benefits one species and neither helps nor harms the other
8 Commensalism A tree with a commensal fern The fern benefits by growing on the tree, which is unaffected by the presence of the fernFigure 41.2 A tree with a commensal fern. The fern benefits by growing on the tree, which is unaffected by the presence of the fern.
9 Types of Two-Species Interactions Type of Interaction Species 1 Species 2Commensalism Helpful NoneMutualism Helpful HelpfulInterspecific competition Harmful HarmfulPredation, herbivoryparasitism, parasitoidism Helpful Harmful
10 SymbiosisSymbiosis (“living together”) refers to a relationship in which two species have a prolonged close associationTwo species that interact closely for generations can coevolve – an evolutionary process in which each species acts as a selective agent on the othersymbiosisOne species lives in or on another in a commensal, mutualistic, or parasitic relationship
11 Key Concepts Community Characteristics A community consists of all species in a habitatA habitat’s history, its biological and physical characteristics, and interactions among species in the habitat affect the number of species in the community and their relative abundance
12 41.3 MutualismIn a mutualistic interaction, two species benefit by taking advantage of one anotherExample: Pollinators eat nectar and pollen, and plants receive pollen from other plants of the same speciesmutualismSpecies interaction that benefits both species
13 Mutualism and Coevolution In some mutualisms, neither species can complete its life cycle without the otherExample: Yucca plants and the moths that pollinate themThe moth matures when yucca flowers bloomMouthparts of the female moth are specialized to collect yucca pollenFemale flies to another flower, pierces its ovary, and lays eggs inside – fertilizing the yucca as she leavesMoth eggs develop into larvae in the ovary of the yucca
14 Yucca Plant and Yucca Moth Figure 41.3 Mutualism on a rocky slope of the high desert in Colorado. Only one yucca moth species pollinates plants of each Yucca species; each moth cannot complete its life cycle with any other plant. The moth matures when yucca flowers blossom. The female has specialized mouthparts that collect and roll sticky pollen into a ball. She flies to another flower and pierces its ovary, where seeds will form and develop, and lays eggs inside. As the moth crawls out, she pushes a ball of pollen onto the flower’s pollenreceiving platform. After pollen grains germinate, they give rise to pollen tubes, which grow through the ovary tissues and deliver sperm to the plant’s eggs. Seeds develop after fertilization. Meanwhile, moth eggs develop into larvae that eat a few seeds, then gnaw their way out of the ovary. Seeds that larvae do not eat give rise to new yucca plants.
15 Mutualism and Defense For some mutualists, the main benefit is defense Example: Sea anemone and anemone fishAn anemone fish has a mucus layer that shields it from stinging cells (nematocysts) of a sea anemoneTentacles of the anemone protect the fish from predatorsThe anemone fish chases away the few fishes that are able to eat sea anemone tentacles
16 Sea Anemone and Anemone Fish Figure 41.4 The sea anemone Heteractis magnifica has a mutualistic association with the pink anemone fish (Amphiprion perideraion). This tiny but aggressive fish chases away predatory butterfly fishes that would bite off tips of anemone tentacles. The fish cannot survive and reproduce without the protection of an anemone. The anemone does not need a fish to protect it, but it does better with one.
17 Mutualistic Microorganisms Mutualistic microorganisms help plants obtain nutrients:Nitrogen-fixing bacteria on roots of legumes (peas) provide the plant with extra nitrogenMycorrhizal fungi living in or on plant roots enhance a plant’s mineral uptakeOther fungi interact with photosynthetic algae or bacteria in lichens
18 41.4 Competitive Interactions Resources are limited and individuals of different species often compete for access to them (interspecific competition)Competition adversely affects both speciesinterspecific competitionCompetition between two species
19 Ecological NicheEach species has an ecological niche defined by physical and biological factors; the more similar the niches of two species are, the more intensely they will competeAn animal’s niches include the temperature range it can tolerate, species it eats, and places it can breedA flowering plant’s niche would include its soil, water, light, and pollinator requirementsecological nicheAll of a species’ requirements and roles in an ecosystem
20 Two Types of Interspecific Competition Exploitative competition:Two species reduce the amount of resources available to the other by using that resourceExample: Deer and blue jays compete for acornsInterference competition:One species actively prevents another from accessing some resourceExample: One species of scavenger will often chase another away from a carcass
21 Interference Competition Figure 41.5 Interspecific competition among scavengers.
22 Interference Competition A Golden eagle and a red fox face off over a moose carcass.B In a dramatic demonstration of interference competition, the eagle attacks the fox with its talons. After this attack, the fox retreated, leaving the eagle to exploit the carcass.Figure 41.5 Interspecific competition among scavengers.Stepped ArtFig. 41.5, p. 694
23 Effects of Competition Species compete most intensely when a shared resource is the main limiting factor for bothWhenever two species require the same limited resource to survive or reproduce, the better competitor will drive the less competitive species to extinction in that habitatcompetitive exclusionProcess whereby two species compete for a limiting resource, and one drives the other to local extinction
24 Experiment: Competitive Exclusion Two Paramecium species compete for the same food (bacteria)Each species thrives when grown aloneWhen grown together, P. aurelia drove P. caudatum to extinctionFigure 41.6 Results of competitive exclusion between two Paramecium species that compete for the same food. When the two species were grown together, P. aurelia drove P. caudatum to extinction.
26 Experiment: Competitive Exclusion Figure 41.6 Results of competitive exclusion between two Paramecium species that compete for the same food. When the two species were grown together, P. aurelia drove P. caudatum to extinction.Fig , p. 695
27 Experiment: Competitive Exclusion Figure 41.6 Results of competitive exclusion between two Paramecium species that compete for the same food. When the two species were grown together, P. aurelia drove P. caudatum to extinction.Fig , p. 695
28 Experiment: Competitive Exclusion Figure 41.6 Results of competitive exclusion between two Paramecium species that compete for the same food. When the two species were grown together, P. aurelia drove P. caudatum to extinction.Fig , p. 695
29 Experiment: Competitive Exclusion Time (days)population densityRelativeP. caudatum aloneTime (days)population densityRelativeBoth species togetherTime (days)population densityRelativeP. aurelia aloneFigure 41.6 Results of competitive exclusion between two Paramecium species that compete for the same food. When the two species were grown together, P. aurelia drove P. caudatum to extinction.Stepped ArtFig. 41.6, p. 695
30 ANIMATION: Competitive Exclusion To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to playMac Users: CLICK HERE
31 Resource Partitioning Resource partitioning is an evolutionary process by which species become adapted to use a shared limiting resource in a way that minimizes competitionExample: Three plant species growing in the same fieldresource partitioningSpecies become adapted in different ways to access different portions of a limited resourceAllows species with similar needs to coexist
32 Resource Partitioning Roots of each species take up water and mineral ions from a different soil depthReduces competition among the species and allows them to coexistFigure 41.7 Resource partitioning among three annual plant species in a plowed but abandoned field. Roots of each species take up water and mineral ions from a different soil depth. This difference reduces competition among the species and allows them to coexist.
33 Character Displacement Directional selection occurs when species with similar requirements share a habitat and compete for a limiting resource, resulting in character displacementExample: Beak sizes in Galapagos finchescharacter displacementOutcome of competition between two speciesDirectional selection shifts the range of variation for one or more traits in a direction that lessens competition for a limiting resource
34 ANIMATION: Hairston's Experiment To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to playMac Users: CLICK HERE
35 ANIMATION: Resource Partitioning To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to playMac Users: CLICK HERE
36 41.5 Predation and Herbivory Predation and herbivory are short-term interactions in which one species obtains nutrients and energy by feeding on anotherpredationOne species (the predator) captures, kills, and eats another species (the prey)
37 Predator and Prey Abundance The abundance of prey species in a community affects how many predators it can supportWith some predators, such as web-spinning spiders, the proportion of prey killed is constantUsually, the number of prey killed depends on the time it takes predators to capture, eat, and digest prey
38 Predator and Prey Abundance (cont.) Predator and prey populations may rise and fall in cyclesExample: Lynx and snowshoe hare populations rise and fall over a ten-year cycleFigure 41.8 Graph of the number of Canadian lynx (dashed line) and snowshoe hares (solid line), based on counts of pelts sold by trappers to Hudson’s Bay Company during a ninety-year period.
39 Lynx and Snowshoe HareFigure 41.8 Graph of the number of Canadian lynx (dashed line) and snowshoe hares (solid line), based on counts of pelts sold by trappers to Hudson’s Bay Company during a ninety-year period.
40 Coevolution of Predators and Prey Predator and prey exert selection pressure on one anotherPredators exert selection pressure that favors improved prey defensesImproved prey defenses in turn exert selection pressure on predators to improve capture skills, and so on
41 Defensive Adaptations Defensive adaptations of prey include hard or sharp parts that make prey difficult to eat, and chemicals that taste bad or sicken predatorsOther adaptations trick or startle an attacking predatorWell-defended prey often have warning coloration that predators learn to avoid, such as the black and yellow stripes of stinging wasps and bees
42 Defensive Adaptations (cont.) In a type of mimicry, prey masquerade as a species that has a defense that they lackExample: Some flies that can’t sting resemble stinging bees or waspsmimicryA species evolves traits that make it more similar in appearance to another species
43 Wasp and MimicFigure 41.9 Mimicry. Some edible insect species resemble toxic or unpalatable species that are not closely related.
44 Predator AdaptationsPredator adaptations include sharp teeth and clawsPredators and prey may be coevolved for speedExample: cheetah and gazelleBoth predators and prey use camouflage (a form, patterning, color, or behavior that allows them to blend into their surroundings) to avoid detection
45 Camouflage in Prey and Predators Figure Camouflage in prey and predators.
46 Coevolution of Herbivores and Plants With herbivory, the number and type of plants in a community can influence the number and type of herbivores presentherbivoryAn animal feeds on plant parts
47 Herbivores and Plants (cont.) There are two types of defenses against herbivory:Some plants have adapted to withstand and recover quickly from herbivoryOther plants have traits such as spines, tough leaves, or toxins that deter herbivoryPlant defenses favor adaptations in herbivoresExample: Koalas have special enzymes to break down toxins in eucalyptus
48 ANIMATION: Predator-Prey Interactions To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to playMac Users: CLICK HERE