Introduction to EcologyChapters 52

Figure 50.3 Rachel Carson

EcologyEcology the study of interactions between organisms and the environmentBiotic living components of an ecosystem (ex. animals and plants) Abiotic - nonliving components of an ecosystem (ex. soil, air, and water)

Species distributionInteractions between organisms and the environment limit the distribution of species.What affects the distribution of species?Dispersal limits (range expansions and species transplants)Behavior and habitat selectionsBiotic factors (other species)Abiotic factors (temperature, water, sunlight, wind, rocks/soil, and climate)

Figure 50.7 Spread of the African honeybee in the Americas since 1956

Figure 50.11 Solar radiation and latitude

Figure 50.12 What causes the seasons?

Figure 50.14 How mountains affect rainfall

Figure 50.18 Zonation in a lake

Figure 50.22 Zonation in the marine environment

Figure 50.24 The distribution of major terrestrial biomes

Figure 50.10 A climograph for some major kinds of ecosystems (biomes) in North America

POPULATION ECOLOGYCHAPTER 53

POPULATION CHARACTERISTICSPopulation organisms of the same species in the same areaDensity number of individuals in a given area (example: 1200/m2)Dispersion pattern of spacing among individuals

Measuring SizeQuadrant method used for stationary organismsMark and recapture used for mobile organisms

Patterns of DispersionClumped individuals aggregated in patches (most common)Uniform evenly spaced individualsRandom unpredictable, patternless

Patterns of dispersion within a populations geographic range

DEMOGRAPHYDemography is the study of factors that affect populationsAge structure relative number of individuals of each ageBirthrate or fecundity number of offspring born during a certain time periodDeath rate number of individuals who die in a certain time periodGeneration time average span between birth of individuals and the birth of their offspringSex ratio proportion of individuals of each sex

Life tables used to determine how long, on average, an individual of a given age could be expected to liveCohort group of individuals of same ageSurvivorship curve a plot of the numbers in a cohort that are alive at each age

Life Table for Belding Ground Squirrels (Spermophilus beldini) at Tioga Pass, in the Sierra Nevada Mountains of California

Idealized survivorship curves

LIFE HISTORIESLife history traits that affect an organisms schedule of reproduction and deathLife histories vary greatlySalmon travel to ocean to mature and then back to stream to reproduceSome oaks cannot reproduce until they are at least 20 years oldSemelparity or big bang reproduction produce numerous offspring and then dieIteroparity or repeated reproduction produce fewer offspring over many seasons

An example of big-bang reproduction: Agave (century plant)

There is a trade-off between reproduction and survivalFemale red deer who are reproductive have a greater chance of dyingLarger brood sizes increase mortality rate

Cost of reproduction in female red deer on the Island of Rhum, in Scotland

Probability of survival over the following year for European kestrels after raising a modified brood

POPULATION GROWTHN = Change in population sizeB = # births during time interval (birth rate)D = # deaths during time interval (death rate)t = time intervalN/t = B DPer capita birthrate (b)= # offspring produced per time by an average member of populationEx. 46 births/year in pop of 1000 so b = 46/1000 = 0.046

Birth rate = Expected # births/year for pop (B):

B=bN

Ex. B = 0.046 x 500 = 23 births/year (where N = 500)

Per capita death rate (m)= # deaths per time by an average member of populationEx. 22 deaths/year in pop of 1000 so m = 22/1000 = 0.022

Death rate = Expected # deaths/year for pop (D):

D=mN

Ex. D = 0.022 x 500 = 11 deaths/year (where N = 500)

Maximum per capita growth rate (rmax)N/t = bN mN (birthrate death rate)r = b mN/t = rmaxN (exponential growth rate)dN/dt = rmaxN (calculus version)

If a population is growing, r is positive.If a population is declining, r is negative.Zero population growth occurs when r = 0Exponential growth maximum population growth rateIntrinsic rate of increase is the maximum population growth rate, rmaxExponential growth is:dN/dt = rmax N

Population growth predicted by the exponential model

Example of exponential population growth in nature

Carrying capacity (K) maximum population size that a particular environment can support with no net increase or decreaseLogistic Growth incorporates the effect of population density on rmax, allowing it to vary from rmax under ideal conditions to zero as carrying capacity is reached.

When N is small compared to K, the per capita rate of increase is high. (N = pop size)When N is large and resources are limiting, the per capita rate of increase is small.When N = K, pop stops growing.For logistic growth:N/t = rmaxN (K-N/K)

Population growth predicted by the logistic model

How does the logistic curve fit real populations?Some populations closely follow the S-shaped curve.Other populations do not.Low numbers may hurt a population (rhinos)Populations may overshoot the carrying capacity and then drop below K.

How well do these populations fit the logistic population growth model?

StrategiesK-selected populations (density dependent)organisms that are likely to be living at density near the limit imposed by the environment (K)r-selected populations (density indepedent)organisms that are likely to be living in variable environments in which populations fluctuate or in open habitats where individuals are likely to face little competition

Characteristicsr-selectedK-selectedMaturation timeShortLongLifespanShortLongDeath rateOften highUsually low#offspring/episodeManyFew# reproductions/lifetimeUsually oneOften severalTiming 1st reproductionEarly in lifeLate in lifeSize of offspring/eggsSmallLargeParental carenoneOften extensive

POPULATION LIMITING FACTORSLimiting factors factors that limit population growthDensity dependent factors death rate rises or birth rate falls with increasing pop densityDiseasePredationCompetitionLack of foodLack of spaceDensity independent birth rate or death rate that does not change with pop densityClimate

Decreased survivorship at high population densities

Long-term study of the moose (Alces alces) population of Isle Royale, Michigan

Extreme population fluctuations

Population cycles in the snowshoe hare and lynx

Human population growth

Demographic transition in Sweden and Mexico, 1750-1997

Age-structure pyramids for the human population of Kenya (growing at 2.1% per year), the United States (growing at 0.6% per year), and Italy (zero growth) for 1995

Annual percent increase in global human pop (data from 2005). Sharp dip in 1960 due mainly to famine in China that killed 60 million people.

Infant mortality and life expectancy (from 2005)

COMMUNITY ECOLOGYCHAPTER 54

COMMUNITIESCommunities different populations living within the same areaWhat factors are most significant in structuring a community?

INTERACTIONSInterspecific interactions occur between different populations within a communityCoevolution a change in one species acts as a selective force on another species, and counter-adaptation by the second species, which may cause a selective force on the 1st species.

Predation (+/-)Lion hunting, killing, and eating a zebraParasitism (+/-)Ticks sucking blood of humanCompetition (-/-)Fighting over resourcesCommensalism (+/0)Birds feeding on insects which bison flush out of grassMutualism (+/+)Legumes with nitrogen fixing bacteriaHerbivory (+/-)Insects eating plantsDisease (pathogens) (+/-)Bacteria, viruses, protists, fungi, and prions

Figure 53.x2 Parasitic behavior: A female Nasonia vitripennis laying a clutch of eggs into the pupa of a blowfly (Phormia regina)

Figure 53.9 Mutualism between acacia trees and ants. The ants live in the hollow thorns and sting other pests.

PredationCryptic coloration camouflageAposematic coloration when animals with effective chemical defenses are brightly colored as a warning

Figure 53.5 Camouflage: Poor-will (left), lizard (right)

Figure 53.6 Aposematic (warning) coloration in a poisonous blue frog

Figure 53.x1 Deceptive coloration: moth with "eyeballs"

Mimicry an organisms mimic anotherBatesian mimicry a harmless species mimics a harmful or unpalatable speciesMullerian mimicry two or more aposematically species resemble each other

Figure 53.7 Batesian mimicry: the hawkmoth larva resembles a snake

Figure 53.8 Mllerian mimicry: Cuckoo bee (left), yellow jacket (right)

CompetitionCompetitive exclusion principle two species with similar needs for the same limiting resources cannot coexist in the same place. Could lead to extinction of one speciesEcological niche ecological role; the sum total of the organisms use of biotic and abiotic resources

Resource partitioning sympatric (geographically overlapping) species consume slightly different foods or use resources in slightly different ways.Character displacement characteristics are more divergent in sympatric populations compared to geographically isolated (allopatric) populations

Figure 53.3a Resource partitioning in a group of lizards

Figure 53.2 Testing a competitive exclusion hypothesis in the field

Figure 53.3bc Anolis distichus (left) perches on sunny areas and Anolis insolitus (right)perches on shady branches.

What controls community structure?Species diversityFood websDominant speciesKeystone speciesFoundation species

Figure 53.21 Which forest is more diverse?

Species DiversitySpecies diversity considers the following:Species richness number of different speciesSpecies relative abundance proportion each species represents of the total individuals in community

Dominant species most abundant or highest biomassEx. American Chestnut was dominant before 1910, but chestnut blight killed all in N. AmericaInvasive species can become dominantKeystone species a predator that makes an unusually strong impact on community structureKeystone predators maintain higher species diversity by reducing the densities of strong competitors, such that the competitive exclusion of other species does not occurEx. Removing Piaster decreased species diversity. Without piaster, mussels overpopulated and excluded other species,

Figure 53.14b Testing a keystone predator hypothesis

Figure 53.14a Testing a keystone predator hypothesis

Figure 53.15 Sea otters as keystone predators in the North Pacific

Without sea otters, sea urchins do well and eat kelp. Kelp forests are being destroyed. Otters are being eaten by killer whales.

Foundation species - cause physical changes to environmentEx. beaver dam, black rush (grass) helps prevent salt build up in soil of marshes

Bottom-up or Top-down ControlsBottom-up = influence from lower to higher trophic levelsMineral nutrients control the plants, which control the herbivores, which then controls the predatorsTop-down = influence from higher to lower trophic levelsPredators limit herbivores, which in turn limits plants, which affects soil nutrients

DISTURBANCESDisturbances are events such as fire, storms, drought, or human activities that damage communities.Can create opportunities for other speciesHuman disturbance is not always negativeYellowstone fire in 1988 killed old forest, but new plants quickly grew in its wakeDynamic equilibrium hypothesis species diversity depends on the effect of disturbance on the competitive interactions of populations.

Figure 53.16 Routine disturbance in a grassland community

Figure 53.18x2 Forest fire

SUCCESSIONEcological succession transitions in species composition over timePrimary succession when succession begins in an area that is virtually lifeless and has no soil.Lichens and mosses are usually the first macroscopic photosynthesizersCan slowly dissolve rock to make soil, which takes thousands of years

Figure 53.18x1 Large-scale disturbance: Mount St. Helens

Figure 53.19 A glacial retreat in southeastern Alaska

Table 53.2 The Pattern of Succession on Moraines in Glacier Bay

Secondary succession occurs where an existing community has been cleared by some disturbance that leaves soil intact (example fire or volcanoes erupting)Typically pioneer species are r-selected (high birthrates and dispersal)

Figure 53.18 Patchiness and recovery following a large-scale disturbance

ECOSYSTEMSChapter 55

FOOD WEBS and TROPHIC LEVELSAutotrophs Producers make own foodHeterotrophsPrimary consumers = herbivores = eat producersSecondary consumers = carnivores = eat primary consumersTertiary consumers = carnivores = eat secondary consumersDetritivores (decomposers) = eat detritus (nonliving organic material and dead remains)

Figure 54.1 An overview of ecosystem dynamics

Section 3-2A Food Web

Figure 54.2 Fungi decomposing a log

Production rate of incorporation of energy and materials into the bodies of organismsConsumption metabolic useDecomposition breakdown of organic material into inorganic

ENERGY FLOW IN ECOSYSTEMSMost solar radiation is absorbed, reflected, or scattered in the atmosphere of Earth.Only a very small portion of sunlight is used by algae, bacteria, and plants for photosynthesis

Primary productivity amount of light energy converted to chemical energy by autotrophs in an ecosystem in a given time periodGross primary productivity (GPP) total primary productivity (not all of this energy is stored in autotrophs because autotrophs use energy for respiration)Net primary productivity (NPP)NPP = GPP RWhere R = the amount of energy used in respiration

C6H12O6 + 6O2 6CO2 + 6H2OGross primary productivity results from photosynthesisNet primary productivity is the difference between the yield of photosynthesis and the consumption of fuel in respirationRespirationPhotosynthesis

Primary productivity J/m2/yr (energy measured per area per unit time)g/m2/yr (biomass added per area per unit time)Seasonal changes and available nutrients can limit primary productivity

Figure 54.3 Primary production of different ecosystems

Figure 54.4 Regional annual net primary production for Earth

Limiting nutrient the nutrient that must be added to increase primary productivity Example: nitrogen or phosphorus are often limiting in aquatic systems (especially in the photic zone)Secondary productivity rate at which an ecosystems consumers convert chemical energy into their own new biomass

Figure 54.9 Nutrient addition experiments in a Hudson Bay salt marsh

Figure 54.11 An idealized pyramid of net production

ECOLOGICAL PYRAMIDSPyramid of productivity~10% rule - ~10% of energy at one level transfers to next levelWhere does the energy go?

Figure 54.10 Energy partitioning within a link of the food chain

Pyramid of biomass standing crop biomass (total dry weight)Some aquatic systems show inverted pyramids because zooplankton consume phytoplankton quicklyProductivity still upright

Figure 54.12 Pyramids of biomass (standing crop)

Figure 54.13 A pyramid of numbers

NUTRIENT CYCLINGBiogeochemical cycles involve both abiotic and biotic components

Figure 54.16 The water cycle

Figure 54.17 The carbon cycle

CARBON CYCLECarbon dioxide in atmosphere is lowest in summer in N. hemisphere and highest in winter. More plants in summer = less CO2 in atmosphereDissolved CO2 makes carbonic acid (H2CO3)

Increased burning of fossil fuels has increased CO2 levels, which leads to global warming.Carbon dioxide absorbs much of the reflected infrared radiation = greenhouse effect.Without the greenhouse effect, temperature would be 18C.

Figure 54.26 The increase in atmospheric carbon dioxide and average temperatures from 1958 to 2000 (readings taken from Mauna Loa, Hawaii)

Global WarmingA number of studies predict CO2 will double by end of 21st century.Will cause a predicted 2C average global temp increaseHistorically, a 1.3 C would make world warmer than any time in past 100,000 years.Poles probably most affected and polar ice melting may change our coastlines!

Figure 54.18 The nitrogen cycle

NITROGEN CYCLEPlants cannot use N2 (gas).Nitrogen fixing bacteria convert nitrogen gas into a form of N that plants can use: ammonium (NH4+) or nitrate(NO3-).Nitrogen fixing bacteria can live in the soil or in plants called legumes (mutualism).Legumes include beans, alfalfa, and soy.Denitrifying bacteria convert nitrate back into nitrogen gas.Without nitrogen fixing bacteria, plants could not get the nitrogen they need and would die. All life on earth depends on these bacteria.

Figure 54.19 The phosphorous cycle

PHOSPHORUS CYCLEPhosphorus is often the limiting nutrient in lakes.Sewage and runoff provide excess phosphorus. This can cause eutrophication. This is when a lake develops a high productivity, which is supported by high rates of nutrient cycling. This leads to algal blooms, which can suffocate the lake.

Figure 54.8 The experimental eutrophication of a lake

Figure 54.24 Weve changed our tune

BIOLOGICAL MAGNIFICATIONNonbiodegradable substances become more concentrated in increasing, successive trophic levels.The biomass at any given level is produced from a much larger biomass ingested from the level below.Example: DDT caused birds of prey to lay eggs with thin shells.

Figure 54.25 Biological magnification of DDT in a food chain

Chlorinated HydrocarbonsInclude DDT, agent orange, PCBs (polychlorinated biphenyls)They are persistent (i.e., they persist in the environment for several years) They are non-polar (i.e., water-hating) They bioaccumulate (i.e., they concentrate in the fat of organisms, and their concentration increases as one moves up the food chain) They are causing a toxic effect at low concentrations

Agent Orange was a defoliant used during the Vietnam War. Agent Orange is an herbicide that was used during the Vietnam War to strip the land of vegetation making it easier for the US troops to see the opposing forces and also to deplete their food supply. Dioxin is a very toxic chemical within Agent Orange. Dioxin is believed to be the cause of so much damage and has been linked to many cancers and birth defects.

Dioxin (part of Agent Orange)

OZONE DEPLETIONOzone (O3) provides a protective barrier to UV light.Chlorofluorcarbons react with O3 and reduce it to O2, which makes holes in the layer.Largest hole over Antarctica. Chlorofluorcarbons come from refrigerants, propellants in aerosol cans, and in some manufacturing processes.

Figure 54.27a Erosion of Earths ozone shield: The ozone hole over the Antarctic

Figure 54.27b Erosion of Earths ozone shield: Thickness of the ozone layer

Grows for years, makes flowering stalk at end to make and release lots of seeds and then dies*