Presentation on theme: "Biodiversity, Species Interactions, and Population Control"— Presentation transcript:
1Biodiversity, Species Interactions, and Population Control Chapter 5
2Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? HabitatHunted: early 1900sPartial recoveryWhy careabout sea otters?EthicsKeystonespeciesTourism dollars
3Case Study: Sea Otters Are They Back From the Brink of Extinction Sea otters a tool-using mammals, uses stones to prey shellfish off rocks underwater and to break open the shells while swimming on the their backs and using their bellies as a table. They consume a ¼th of their weight each day in sea urchins, clams, mussels, crabs, abalones and about 40 other species of bottom-dwelling organisms. . They are the only marine mammal that lacks blubber, they can trap air under their fur for insulation. Early 1900’s almost extinct. They were hunted for fur and because they competed with fishers for valuable abalone declared endangered. Most remaining species are found between California’s coastal cities of Santa Cruz and Los Angeles.(a) Southern sea otter(b) Sea Urchin(c) Kelp bed
45-1 How Do Species Interact? Concept 5-1 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.
5Most Species Compete with One Another for Certain Resources Competition the struggle among organisms, both of the same and of different species, for food, space, and other vital requirements.Competitive exclusion principle The principle that when two species compete for the same critical resources within an environment, one of them will eventually outcompete and displace the other. The displaced species may become locally extinct, by either migration or death, or it may adapt to a sufficiently distinct niche within the environment so that it continues to coexist noncompetitively with the displacing species.
6Species Interact in Five Major Ways Interspecific CompetitionPredationParasitismMutualismCommensalism
7Interspecific competition Competition between two different speciesFor food, sunlight, water, soil, spaceOne species may migrate or shift feeding habits or face extinctionExample-native ants and nonnative fire antsIntraspecific competitioncompetition between members of the same speciesNatural capital: resource partitioning and niche specialization as a result of competition between two species. The top diagram shows the overlapping niches of two competing species. The bottom diagram shows that through evolution the niches of the two species become separated and more specialized (narrower) so that they avoid competing for the same resources.
8Most Consumer Species Feed on Live Organisms of Other Species Predators may capture prey byPursuitWalkingSwimmingFlyingPursuit and ambushCamouflageChemical warfare
14Most Consumer Species Feed on Live Organisms of Other Species Prey may avoid capture byCamouflageChemical warfareWarning colorationMimicryDeceptive looksDeceptive behaviorSwift movementShell
15Some ways prey species avoid their prey Span wormWandering leaf insectBombardier beetleFoul-tasting monarchbutterflyPoison dart frogViceroy butterfly mimicsmonarch butterflyWhen touched, thesnake caterpillarchanges shape to looklike the head of a snakeHind wings of mothresemble eyes of amuch larger animalSome ways prey species avoid their prey
23Parasitism Live on or in another species Host is harmed Ex. Tapeworms, ticks, fleas, mosquitoes, candiru (vampire fish)
24Mutualism (benefits both species) Pollination mutualism (between flowering plants and animals)Nutritional mutualismLichens grow on treesBirds/rhinos- nutrition and protectionClownfish/sea anemonesInhabitant mutualismVast amount of organisms like bacteria in an animal’s digestive tractTermites and bacteria in gut
25.Coral Reefs- The corals get food and the zooxanthellae (algae) get protection.zooxanthellae
26Yucca and Yucca MothYucca’s only pollinator is the yucca moth. Hence entirely dependent on it for dispersal.Yucca moth caterpillar’s only food is yucca seeds.Yucca moth lives in yucca and receives shelter from plant.Example of co evolution
27Oxpeckers and black rhinoceros Clown fish and sea anemone Figure 8-10 Page 155Oxpeckers and black rhinocerosClown fish and sea anemoneExamples of MutualismMycorrhizae fungi on juniperseedlings in normal soilLack of mycorrhizae fungi onjuniper seedlings in sterilized soil
28Commensalism Helps one species but does nothing for the other CommensalismHelps one species but does nothing for the otherEx. Redwood sorrel grows in shade of redwood- Humans and Eyelash Mites
29Science Focus: Why Should We Care about Kelp Forests? Kelp forests: biologically diverse marine habitatMajor threats to kelp forestsSea urchinsPollution fromwater run-offGlobal warming
305-2 How Can Natural Selection Reduce Competition between Species? Concept 5-2 Some species develop adaptations that allow them to reduce or avoid competition with other species for resources.
31Some Species Evolve Ways to Share Resources Resource partitioningReduce niche overlapUse shared resources at differentTimesPlacesWays
32Resource partitioning Evolve more specialized traitsSharing the wealth: resource partitioning of five common species of insect-eating warblers in the spruce forests of Maine. Each species minimizes competition with the others for food by spending at least half of its feeding time in a distinct portion (shaded area) of the spruce trees, and consuming somewhat different insect species.Five species of common insect-eating warblers in the Spruce forests of Maine
335-3 What Limits the Growth of Populations? Concept 5-3 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.
34Characteristics of a Population Population - individuals inhabiting the same area at the same timePopulation Dynamics: is the study of how population change due toPopulation Size - number of individualsPopulation Density - population size in a certain space at a given timePopulation Dispersion - spatial pattern in habitatAge distribution - proportion of individuals in each age group in population
35Populations Have Certain Characteristics Changes in population characteristics due to:TemperaturePresence of disease organisms or harmful chemicalsResource availabilityArrival or disappearance of competing species
36Population Size Natality Mortality Number of individuals added through reproductionCrude Birth Rate - Births per 1000Total Fertility Rate – Average number of children born alive per woman in her lifetimeMortalityNumber of individuals removed through deathCrude Death Rate- Deaths per 1000
37Population DensityPopulation Density (or ecological population density) is the amount of individuals in a population per unit habitat areaSome species exist in high densities - MiceSome species exist in low densities - Mountain lionsDensity depends uponsocial/population structuremating relationshipstime of year
38Population Dispersion Population dispersion is the spatial pattern of distributionThere are three main classificationsClumped: individuals arelumped into groupsex. Flocking birds orherbivore herds due toresources that are clumpedor social interactionsmost common
39Most Populations Live Together in Clumps or Patches Why clumping?Species tend to cluster where resources are availableGroups have a better chance of finding clumped resourcesProtects some animals from predatorsPacks allow some to get preyTemporary groups for mating and caring for young
40Population Dispersion Uniform: Individuals are regularly spaced in the environment - ex. Creosote bush due to antagonism between individuals, or do to regular spacing of resources rare because resources are rarely evenly spacedtips/2002/clover611.htmRandom: Individuals are randomly dispersed in the environment ex. Dandelions due to random distribution of resources in the environment, and neither positive nor negative interaction between individuals rare because these conditions are rarely metUniform penguins often exhibit uniform spacing by aggressively defending their territory among their neighbors.The leaves of the creosote bush are coated with a resin to prevent water loss in the hot desert. The resin of the creosote bush also protects the plant from being eaten by most mammals and insects. It is believed that the bush produces a toxic substance to keep other nearby plants from growing. Creosote bushes are very long lived, many of them existing for one hundred years, and can grow to a height of 15 feet.Random Tropical fig trees exhibit random distribution as well because of wind pollination. oyster larvae can travel hundreds of kilometers powered by sea currents, which causes random distribution when the larvae land in random places
41Age StructureThe age structure of a population is usually shown graphicallyThe population is usually divided up into prereproductives, reproductives and postreproductivesThe age structure of a population dictates whether is will grow, shrink, or stay the same size
43Population change= (Birth + Immigration)- (Death + Emigration) Four variables influencing growthBirthsDeathsImmigrationEmigrationIncrease by birth & immigrationDecrease death & emigrationPopulation change= (Birth + Immigration)-(Death + Emigration)
44No Population Can Grow Indefinitely: J-Curves and S-Curves (1) Biotic potential - is the population’s capacity for growthLow generally large animals elephant and blue whalesHigh small individuals like bacteria and insectsIntrinsic rate of increase (r) is the rate of population growth with unlimited resources.
45Rapidly growing populations have four characteristics (high r) Reproduction early in lifeShort periods between generationsLong reproductive livesMultiple offspring each time they reproduceA single house fly couldtotal 5.6 trillion house flieswithin 13 months
46No Population Can Grow Indefinitely: J-Curves and S-Curves (2) Size of populations limited byLightWaterSpaceNutrientsExposure to too many competitors, predators or infectious diseases
47Environmental Resistance Consists of all factors that act to limit the growth of a populationAbiotic Contributing Factors:Unfavorable lightUnfavorable TemperaturesUnfavorable chemical environment - nutrientsBiotic Contributing Factors:Low reproductive rateSpecialized nicheInability to migrate or disperseInadequate defense mechanismsInability to cope with adverse conditions
49Limits on population growth Carrying capacity [K] determined by biotic potential & environmental resistanceThis is the # of a species’ individuals that can be sustained indefinitely in a specific spaceAs a population reaches its carrying capacity, its growth rate will decrease because resources become more scarce.
50No population can grow forever No population can grow forever. Exponential growth (lower part of the curve) occurs when resources are not limiting and a population can grow at near its intrinsic rate increase ( r ) or biotic potential. Such exponential growth is converted to logistic growth, in which the growth rate decreases as the population gets larger and faces environmental resistance. With time, the population size stabilizes at or near the carrying capacity ( K )of its environment and results in the sigmoid (s-shaped) population growth curve shown in this figure. Depending on resource availability, the size of a population often fluctuates around its carrying capacity.
51Population Growth Populations show two types of growth With few resource limitationsExponentialJ-shaped curveGrowth is independent of population densityThe growth rate levels off as population reaches carrying capacityLogisticS-shaped curveGrowth is not independent of population density
53Science Focus: Why Are Protected Sea Otters Making a Slow Comeback? Low biotic potentialPrey for orcasCat parasitesToxic algae bloomsPCBs and other toxinsOil spillsSexual yearsReproduce until age 15 one pup a yearOrcas main prey seals numbers have been decliningCat owners have been flushing cat litter or dump in storm drains enters the coastal watersAlgea blooms from bird guano
54When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash Carrying capacity: not fixedReproductive time lag may lead to overshootDieback (crash)Damage may reduce area’s carrying capacity
55Populationovershootscarryingcapacity2,000Population crashes1,500Number of reindeer1,000CarryingcapacityWhen 26 reindeer (24 of them females) were introduced in 1910, lichens, mosses, and other food sources were plentiful. By 1935, the herd population had soared to 2,000 overshooting the islands carrying capacity. This lead to a population crash, with the herd plummeting to only 8 reindeer by 1950.50019101920193019401950YearExponential growth, overshoot, and population crash of reindeer introduced to a small island off of SW Alaska
56Reproductive Strategies Goal of every species is to produce as many offspring as possibleEach individual has a limited amount of energy to put towards life and reproductionThis leads to a trade-off of long life or high reproductive rateNatural Selection has lead to two strategies for species: r - strategists and K - strategists
57r - Strategists Spend most of their time in exponential growth High rate of reproductionLittle parental careMinimum lifeOpportunistK
58R Strategists Many small offspring Little or no parental care and protection of offspringEarly reproductive ageMost offspring die before reaching reproductive ageSmall adultsAdapted to unstable climate and environmental conditionsHigh population growth rate – (r)Population size fluctuates wildly above and below carrying capacity – (K)Generalist nicheLow ability to competeEarly successional species
59K - Strategists Maintain population at carrying capacity (K) K Maximize lifespanCompetitorFollow a logistic growth curveK
60K- Strategist Reproduce later in life Fewer, larger offspring High parental care and protection of offspringMost offspring survive to reproductive ageLarger adultsAdapted to stable climate and environmental conditionsLower population growth rate (r)Population size fairly stable and usually close to carrying capacity (K)Specialist nicheHigh ability to competeLate successional speciesProne to extinction
61Genetic Diversity Can Affect the Size of Small Populations Founder effectDemographic bottleneckGenetic driftInbreedingMinimum viable population size- the number of individuals populations need for long term survival
62Effects of Genetic Variations on Population Size Genetic diversity1. Founder effectFew individuals move to a new location and are isolated from the original populationLimited geneticdiversity
632. Demographic bottleneck Few individuals survive a catastrophe- fire, hurricaneLack of genetic diversity may limit these individuals to rebuild the population
643. Genetic drift 4. Inbreeding Random changes in gene frequencies May help or hurt survival of a populationSome individuals may breedmore than others and theirgenes may eventually dominate the gene pool of the population4. InbreedingMembers of a small population exchange genes
65Density of a population density Density-independent (affects population size regardless of its density)Floods, hurricanes, fire, pesticide spraying , pollution)Density-dependent (greater effect as population density increases)Competition for resources, predation, parasitism, disease – bubonic plague)
66Population fluctuations in nature Stable (varies slightly above and below carrying capacity,K)Irruptive (explode to a high level and then drastically drop - insects)Cyclic (over a regular time period – lemmings populations rise and fall ever 3-4 years)Irregular behavior (no pattern)
68Population size (thousands) 160Hare140Lynx120100Population size (thousands)80604020For decades, predation has been the explanation for the 10-year population cycle of the snowshoe hare and its predator, the Canadian Lynx. According to this top-down control hypothesis, lynx preying on hares periodically reduced the hare population. The shortage of hares then reduced the lynx population, which allows the hare population to build up again. At some point the lynx population increases to take advantage of the increased supply of hares, starting the cycle again. However, researchers have found that snowshoe hare have a 10 year boom-and-bust cycles on islands where lynx are absent. These scientist hypothesizes that the periodic crashes in the hare population can also be influenced by their food supply. Once the hare populations crash the plants can recover and the hare population begins rising again. If this bottom-up control theory is correct the lynx do not control the hare population. Instead, the changing hare population size may cause fluctuations in the lynx populations. It more than likely a combination of the two factors, predation and food supplies.1845185518651875188518951905191519251935YearPredator – prey relationshipsLynx-Hare CycleCyclic ever 10 years
69Humans Are Not Exempt from Nature’s Population Controls IrelandPotato crop in 18451 million people died from hunger or disease form malnutrition3 million migrated to other countries (mainly U.S.)Bubonic plagueFourteenth centuryKilled a least 25 million people in European CitiesAIDSGlobal epidemicBetween AIDS has killed more than 25 million peopleClaims 2.1 million a year ( average of 4 deaths per min.)
70Case Study: Exploding White-Tailed Deer Population in the U.S. 1900: deer habitat destruction and uncontrolled hunting1920s–1930s: laws to protect the deerCurrent population explosion for deerLyme diseaseDeer-vehicle accidentsEating garden plants and shrubsWays to control the deer population
715-4 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? Concept 5-4 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.
72Communities and Ecosystems Change over Time: Ecological Succession Natural ecological restorationPrimary succession is ecological succession in a bare area that has never been occupied by a community of organisms.Bare rock exposed by retreating glacier, severe erosion, newly cooled lava, abandoned concrete/ highway, newly created pondSecondary succession is an ecological succession in an area in which natural vegetation has been removed or destroyed but the soil is not destroyed.forest fires, deforestation, abandoned farmland, heavily polluted streams, and land that has been damned or flooded.
73Succession = change 1. Primary succession Gradual establishment of biotic community on lifeless groundBarren habitatBare rock / retreating glacierA newly- cooled lavaA newly formed pondIt takes several centuries to several thousands of years for natural processes to produce fertile soil.Ex. HawaiiPioneer species (lichens, moss and microbes)
74Some Ecosystems Start from Scratch: Primary Succession No soil in a terrestrial systemNo bottom sediment in an aquatic systemEarly successional plant species, pioneerBacteria, moss, lichensMidsuccessional plant speciesHerbs and shrubsLate successional plant speciesBalsam fir, paper birch, and white spruce
76Primary Succession Balsam fir, paper birch, and white spruce ExposedrocksLichensand mossesBalsam fir,paper birch, andwhite spruceclimax communityPrimary succession is ecological succession in a bare area that has never been occupied by a community of organisms.Primary Succession the ground is nearly lifeless; no soil present in a terrestrial ecosystem; no bottom sediment in an aquatic ecosystemBare rock exposed by retreating glacier, severe erosion, newly cooled lava, abandoned concrete/ highway newly created pondJack pine,black spruce,and aspenHeath matSmall herbsand shrubsTime
77Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession Some soil remains in a terrestrial systemSome bottom sediment remains in an aquatic systemEcosystem has beenDisturbedRemovedDestroyed
79Mature oak-hickory forest Secondary SuccessionMature oak-hickory forestSecondary succession is an ecological succession in an area in which natural vegetation has been removed or destroyed but the soil is not destroyed.Secondary Succession: a biotic community is already present; soil or bottom sediment is presentExamples, forest fires, deforestation, abandoned farmland, heavily polluted streams, and land that has been damned or flooded.Young pine forestPerennialweeds andgrassesShrubsAnnualweedsTime
80Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (2) Primary and secondary successionTend to increase biodiversityIncrease species richness and interactions among speciesPrimary and secondary succession can be interrupted byFiresHurricanesClear-cutting of forestsPlowing of grasslandsInvasion by nonnative species
81Succession of an Aquatic Ecosystem Aquatic ecosystem gradually increasing in sedimentation/inflow of nutrients from surrounding land areasSlowly filling w/ silt, sand and other particles; shoreline gradually advances toward the center of the pond;Aquatic vegetation contributing to this fillingIn a “classic scenario” the pond would eventually become a wetland, then perhaps a grassland, followed by some type of forest.
83Science Focus: How Do Species Replace One Another in Ecological Succession? 1. FacilitationOne species makes an area of suitable for another speciesEx. Moss build land for grasses2. InhibitionEarly species limit later speciesEx. Plants may release toxins3. ToleranceLater species are unaffected by earlier species
84Succession Doesn’t Follow a Predictable Path Traditional viewBalance of nature and a climax communityCurrent viewEver-changing mosaic of patches of vegetationMature late-successional ecosystemsState of continual disturbance and change
85Living Systems Are Sustained through Constant Change Inertia, persistenceAbility of a living system to survive moderate disturbancesResilienceAbility of a living system to be restored through secondary succession after a moderate disturbanceTipping pointWhere any additional stress can cause the system to change in an abrupt and usually irreversible way
86The Cats of BorneoWhat happened first?Arrange the sentence strips in chronological order
87Operation Cat DropOne of the most bizarre events to accompany this early use of DDT occurred when it became necessary to parachute cats into remote jungle villages in what was then Burma. The following account was taken from a source at Cornell University:In the early 1950s, the Dayak people in Borneo suffered from malaria. The World Health Organization had a solution: they sprayed large amounts of DDT to kill the mosquitoes which carried the malaria. The mosquitoes died, the malaria declined; so far, so good. But there were side-effects. Among the first was that the roofs of people's houses began to fall down on their heads. It seemed that the DDT was also killing a parasitic wasp which had previously controlled thatch-eating caterpillars. Worse, the DDT-poisoned insects were eaten by geckoes, which were eaten by cats. The cats started to die, the rats flourished, and the people were threatened by outbreaks of sylvatic plague and typhus. To cope with these problems, which it had itself created, the World Health Organization was obliged to parachute14,000 live cats into Borneo.
88The Day they Parachuted Cats into Borneo WHO sent DDT to Borneo.Mosquitoes were wiped out.Caterpillar numbers went up.Caterpillars ate grass roofs.Roaches stored DDT in their bodies.Lizards ate roaches and got DDT.Lizards slowed down.Cats caught lizards containing DDT.Lizards disappeared.Cats died.Rats increased.Rats brought the plague.Cats were parachuted in.