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61 Cards in this Set

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What is Ecology? Our working definition:

The study of the environmental factors that determine the distributionand abundance of organisms

Effect of abiotic environment on the distribution of organisms

o Global climate and biome distributions


o The physical environment and speciesdistribution


o Adaption and acclimatization

What is a biome?




Why do biomes occur a certain latitudes?

An ecological community that extends over a large area and ischaracterized by a dominant vegetation




Climate, distribution can be predicted by precipitation and temperature. Curvature of the earth results in changeof precipitation and temperature laterally. More solar energy/m2hits the earth at low latitudes then high latitudespTlEi4

Temperature and Seasonality

Warm air can hold more moisture then coldair




Temperature effects air circulationpatterns




Seasonality in temperature is higher atthe poles and lower at the equator. Seasonal variation is due to the tilt ofthe earth axis




The tilt of earth’s axis also causesseasonal variation in precipitation




Inter-tropicalconvergente zone (ITCZ)




Hadley cells: seasonal rain cells shiftingaround the tropics of cancer and Capricorn

Why do different climates and thus biomes occur at the same latitude?

OCEAN CURRENTS: Warm ocean currents causebiomes to occur at higher latitudes then they would otherwise


MOUNTAINS:temperature is lower at higher altitudes because the air is less dense and canhold less energy. Rain shadows because drier climates on the east side ofmountain ranges (mostly seen on Western ranges). At high altitudes you seebiomes characteristics of higher latitudes. EX- At the same altitude SanFrancisco peaks have tundra, Mt. Kilimanjaro in Kenya has Boreal forest

Will plants transpire more in higher or lower water saturated air?

When the air is less saturated with water,plants will transpire more: When air outside the plant is less saturated withwater than the air inside the plant = more movement of water from the soil tothe atmosphere (transpiration). When plants transpire more they photosynthesize more.

How do we estimate the transpiration (and by extension photosynthesis)at the whole biome level?

POTENTIAL EVAOTRANSPIRATION (PET), the potential amount of water thatcan move from the soil to the atmosphere at a given temperature




The mean temperature and precipitation ofa location can be summarized using a climate diagram.




On a temperature and precipitation climate graph PET = approx. 2 xtemperaturepT n

Whats AET?




How are AET and PET linked?

Actual evapotranspiration (AET) determinesthe productivity of a biome




Net primary production = the amount ofenergy that plants are able to capture from the sun via photosynthesis, minusthe energy used for respiration




Can’t have a higher AET then rainfall. If rainfall > PET the AET = PET. If rainfall < PET the AET < PET

What are the 3 types of sampling?

Haphazard: select arbitrary or convenientsites/individuals




Random: randomly select sites/individualsTHE MOST ACCURATE




Systematic: select sites/individuals atregular intervals

The biome a species occurs in is dependenton the species physiological tolerance. Physiological tolerance is estimated usingperformance curves. Why do species have different curves?

Acclimation: short term physiologicaladjustment that occurs in response to




Adaption: the evolution via naturalselection of traits that increase performance in a specific environment

What is the Common Garden Experiment?

Rear organisms from different populationsof species in common environment


Estimate their performance curves


If organisms STILL have differentperformance curves when reared in a common environment; then conclude thatdifferences in curves are result of adaption


If differences in performances curves areNOT maintained in a common environment, then conclude that difference in thecurves are the result of acclimation

Whats the difference between acclimation and adaption?

KEY DIFFERENCE between adaption andacclimation is time scale, they CAN work together




Distinguishing between adaption and acclimation to the physicalenvironment: Variation in common garden persists in a common garden indicatingthat it is caused by adaption

What is the heat balance equation?




And what are its components?

The heat balance equation:


HNET= HAR + HMET – HRR +/- HCOND +/- HCONV- HE




HNET the net heat gain


HAR absorbed radiation


HMET metabolic heat


HRR re-radiated heat which islost


HCOND heat gained or lost viaconduction


HCONV heat gained or lost viaconvection


HE evaporative heat lost

What does surface area have to do with heat balance? Allen's rule...

Surface area to volume ratio:


Less compact shapes have a higher SA:Vratio


More compact shapes have a lower SA:Vratio


Smaller shapes have a higher SA:V ratio


Larger shapes have ahigher SA:V




Allen’s rule (1877): surface area tovolume ratio and the distribution of species. Endotherms from warm climates have longerthinner extremities thus higher SA:V ratios

Experimental Studies

Experiments and experimental design,cannot rule out unmeasured variables. Possibilities of other influence. In an experimental study, ecologistsmanipulate the biota or abiotic environment, and measure ow organisms respondto the manipulation. Pros: experimental studies can definitelydetermine cause and effect. Cons: experimental studies can belogistically challenging

What is the water balance equation? And what are its components?

WATER BALANCE EQUATION:


Water balance = WD+ WF + WA – WE - WS




WD gained by indigestion (d> drink)


WF gained from the metabolismof carbohydrates (f > food)


WA gained through absorption(plants)


WE last through evaporation(i.e. sweat)


WS lostthrough secretion (urination and defecation)

Why can’t organisms eliminate all water losses?

There is a trade-off between reducedevaporation and metabolic activity


Spiracles and stomata need to remain openso that O2 and CO2 can be exchanged.



The primary challenge to terrestrialorganisms face in maintaining their water balance within metabolic limits isreducing water loss through evaporation (WE)How do terrestrialorganisms maintain water balance within metabolic limits?

Vapor pressure deficit (VPD) estimatesrelative saturation of air with water:


High VPD = high evaporation (lowsaturation of air with water).


Low VPD = low evaporation

How do freshwater organisms maintain their water balance withinmetabolic limits?

Limiting water gain through absorption (loss of salts through the gills;decreases WA through osmosis, production of copiousurine; increased WS

What is the relationship betweenmechanisms of water balance and species distribution?

Drought deciduous: plants that drop theirleaves during drought. The relationship between water balance andspecies distribution: Sapwood area ratio


High leaf: sapwood area ratio vs low leaf:sapwood area ratio, so leaf area is compared to water conducting tissue. Water is a limiting factor! Low leaf : sapwood area ratio is adaptingto low water therefore it should eliminate water loss by evaporation. Low VPD – High leaf : sapwood area ratio. High VPD – Low leaf : sapwood area ratio

Interactions between temperatureregulation and water balance, are there trade-offs between maintaining heat andwater balance?

Because evaporation affects both heat andwater balance, organisms can fare trade-off between


Because SA:V ratios affect both heat andwater balance organisms can face a trade-off between maintaining heat and waterbalance


EVAPORATION is common denominator and SA:Vratio

Experiments and experimental design

Experimental unit: the piece ofexperimental material that you apply treatment to. It might be a singleorganism or multiples in an area, it MUST be possible for any two experimentalunits to independently receive a different treatment.


Treatment: the experimental manipulationthat is applied to the experimental unit. Different treatments can be differentlevels of the factor being examined.


Control: is an experimental unit that doesnot receive a treatment and functions as a baseline to which the treatments arecompared. Ideally the controls and treatments should be applied during the sameperiod of time so that the experimental unit are all experiencing the same environmentalconditions; this is referred to as a contemporaneous control.


Replication: one of several experimentalunits to which you apply the same treatment. You need to have multipleexperimental units that independently receive the treatment in order to avoidbias and to separate out the effect of the treatment from the naturalvariability that is found in nature. Generally the more replicates the better.


Randomization: the random assignment oftreatments to the experimental units rather than using a subjective approachwhich may be biased. Applying the treatment randomly means that eachexperimental unit has an equal probability of being assigned to any of thetreatments.


Response Variables:the “things” measured to determine the effects of the treatments, in otherwords the dependant variable

What is our working definition of a population?




How can we predict whether a population isgoing to increase in size, decrease in size, or stay the same?

A group of organisms of the same speciesoccupying a particular space at a particular timePredicting whether apopulation is going to increase in size, decrease in size, or stay the same hasimportant real-world applications




Population size: Natality, Mortality,Immigration and Emigration

What is life history?




What are the life history traits (6)?

The life history of a species is determinedby the collection of age or stage specific traits that directly affect anindividual's reproductive success. Together these traits are called a life history strategy.




1. Numberof reproductive events per lifetime (one, few, many)


2. Numberof offspring per reproductive event (“clutch size”)


3. Ageat first reproduction


4. Relativelength of life history stages (egg or seed, juvenile, adult)


5. Investmentper offspring (many small versus few large offspring)


6. Theprobability of dying at different life history stages

How do trade-offs constrain life history strategies?

Offspring size and number, current andfuture reproduction

Life tables can be used to summarize lifehistory traits, what are the two types of Lifetables?

1. CohortLife Table: Follow a cohort of individuals from birth to death. Have to waituntil the last individual dies


2. Static Life Table:Take a cross-section of a population. Easier to collect data, but have toassume that birth and death rates are not changing over time

Life Table info

Age in years (x)


Observed # of species alive (nx)


Proportion of organisms survivingfrom the start of the life table to agex (lx) = nx/no


mx = number of female offspring produced per female in each age interval

What are the three types of survivorship curves:

Type I survivorship curves arecharacterized by high age-specific survival probability in early and middlelife, followed by a rapid decline in survival in later life. They are typicalof species that produce few offspring but care for them well, including humansand many other large mammals.




Type II curves are an intermediate betweenTypes I and III, where roughly constant mortality rate/survival probability isexperienced regardless of age. Some birds and some lizards follow this pattern.




In Type III curves,the greatest mortality (lowest age-specific survival) is experienced early inlife, with relatively low rates of death (high probability of survival) forthose surviving this bottleneck. This type of curve is characteristic ofspecies that produce a large number of offspring (see r/K selection theory).This includes most marine invertebrates. For example, oysters produce millionsof eggs, but most larvae die from predation or other causes; those that survivelong enough to produce a hard shell live relatively long

Net reproductive rate?




Generation time?

The net reproductive rate (Ro):Ro = {lxmx




R0 > 1 Population willincrease in size


R0 = 1 Population size will notchange


R0 < 1Population size will decrease




Generation time (T): T = {lmx/ Ron

Intrinsic rate of increase?

Relationship between body size andgeneration time


Intrinsic rate of increase: r = ln(Ro)/ T


r > 0 Population size will increase


r = 0 Population size will be stable


r < 0 Population size will decrease


Ro and r should predict thesame thing


Intrinsic rate of increase can varybetween species and within a species

Factors that increase intrinsic rate of increase? (3)

1. Reductionin age at first reproduction


2. Increasein the number of progeny in each reproductive event


3. Increasein the number of reproductive events

What does density-independent mean?

In a density-independent model, we assume that birth rates and deathrates do not depend on population size

Overlapping generations:




Exponential growth model for overlapping generations:

Parents and offspring alive at the sametime.


Most plant and animal species haveoverlapping generations


To predict growth of populations withoverlapping generations, we can use an exponential growth modelauto;




Nt = Noert or dN/dt = rN

Bottom up and top down control?

FOOD WEBS! Are populations limited by prey(bottom-up) or by predators (top-down)?


Bottom up: population limited by prey


Top down: population limited by predatorsto;

Intraspecific vs. Interspecific

The effects of biotic and abioticenvironment on the distribution and abundance of organisms – intraspecificrelationships




The effects of species interactions on thedistribution and abundance of organisms – interspecific relationships

Models of density-dependent populationgrowth: logistic growth model

dN/dt = rN[1 - (N/K)] where K = carryingcapacity




dN/dt is at its maximum when N=K/2e=T#9i

Types of predation? (6)

1. Herbivores(animals eat plants)


2. Carnivores (animals prey on animals)


3. Insectparasitoids (lay eggs on organisms and consume from inside out)


4. Parasites(live on host – not necessarily killing)


5. Cannibalism(preadators and prey are same species)


6. Intraguild predation(competing for same resource & preying on each other)

Lotka-Volterra Prey Equation?




Capture efficiency?

PREY EQUATION: dNprey/dt = rpreyNprey-aNpreyNpredator


Nprey is # of victims or prey


Npredator is number ofpredators


rprey intrinsic rate ofincrease of prey or victims


a is capture efficiency




Capture efficiency: tells us the effect ofthe predator on the growth rate of the prey


Filter feeding whales have a large captureefficiency (captures a lot of krill massively decreasing prey population)


Web-building spiders have small captureefficiency (spider catches one bug at a time, decreasing prey population only alittle bit)

Lotka-Volterra Predator equation?




Conversion efficiency?

PREADATOR EQAUATION: dNpredator/dt= abNpredatorNprey - mNpredator


b is conversion efficiency


m is death rate of predators


model assumes predator has only one preyspecies available


Death rate of predators: increases whendeath rate is high




Conversion efficiency (b): ability of apredator to convert each prey item (on an individual basis) into new babypredators, value of individual pre items


High when single prey item is particularlyvaluable (wolf and moose- moose allows wolves to make many more pups). Low when a singleprey item is not very valuable (bird and seeds- one seed does not allow thebird to have more chicks

Equilibrium Solution– what is the solutionof this model when population growth rate is 0?

Prey population equilibrium: 0 = rpreyNprey-aNpreyNpredator then Npredator = rprey/a


Whenprey population r is high, N is going to be very high as well


Whenthe capture efficiency (a) is lower, N increases to keep population steadyo




Predator population equation: 0 = abNpredatorNprey- mNpredator then Nprey = m/ab


Higherdeath rate of predators the more prey are needed

What happens to the prey population in the absence of the predatorpopulation?




What happens to the predator population in the absence of the preypopulation?

dNprey/dt = rpreyNprey




dNpredator/dt = -mNpredator

What is rprey/a?

rprey/a is the number of predators needed to keep prey population steady.

Lotka Volterra Models

Allows us to make predictions which we canthen go test. It predicts the cycling effect shown in the graph betweenpredator and prey.




Peaks and troughs are offset by ¼ of acycle

What are the Lotka-Volterra Assumptions (6)?

1. Thereare no effects of crowding for either the prey or predator (i.e., there is nodensity dependence in growth rates).


2. Allpredator and prey individuals are equally likely to meet any of the others(i.e., the populations are evenly spread out and well-mixed, so that prey haveno refuges from predators).


3. Theprey species is the only food source for the predator.


4. Thepredator is the only significant cause of death for the prey. (no death fromdisease etc.)


5. Eachpredator individual can catch and eat prey individuals instantaneously (thereis no handling time).


6. Thereis no immigration or emigration of either prey or predators. (assuming closedpopulations)n

Can predators and prey limit each othersdistributions in the field?




Can predator and prey species coexist inthe lab?

BIOTIC factors controlling speciesdistributions. Preadator prey coexistence in labs: GausesProtozoans – failed to replicate Lotka-Volterra, populations crashed, thereforeadded refugees to culture – caused predator to go extinct and prey to skyrocket. Eventually managed to achieve predatorprey cycle on graphs: had to introduce immigration. Huffackers oranges: made complex universeswith high dispersal of predators and prey, cycle achieved with 252 oranges

Definition of competition

Intra- vs. interspecific competition




Intraspecific competition: members of aspecies use the same limited resource, negatively influencing each other’s populationgrowth rates and population sizes




Interspecific competition: two differentspecies use the same limited resource, negatively influencing each other’s populationgrowth rates and population sizes

Mechanisms of competition

Interferencecompetition: direct interference with each other’s access to a resource Competition by exploitation(resource competition): whichever species can use resource more efficiently




Milkshake analogy: exploitation can suckmilkshake faster and interference can pinch each other’s straws

If resources are limiting in naturalpopulations, how do so many species coexist?




How can we modify the logistic growth model to describe the effect of interspecific competition on population growth?

The logistic growth model describes theeffects of intraspecific competition on population growth dN/dt = rN(1-N/K)




dN1/dt = r1N1[1-(N1+ α 12N2/K1)]


dN2/dt = r2N2[1-(N2+α 21N1/K2)]




Lotka-Volterra model of competition:Equilibrium solutions N1 =K1 – α12 N2,N2 =K2 – α21 N1

Competition coefficients

α12 and α21 = Competition coefficients




If α12 = 1, strength of interspecific andintraspecific are equal


If α12 < 1, intraspecific competitionstronger


If α12 > 1, interspecific competitionstronger

Co-existance Isoclines

To understand the conditions that allow forcoexistence, we need to plot the isoclines for Species 1 and Species 2 on thesame grapho Intercepts!


What conditions cause each to increase anddecrease


Stable equilibrium: coexistence

What does the Lotka-Volterra model tell usabout the conditions that allow competing species to coexist?

If perturbed off equilibrium will not goback. One species will win over the other


Theta for equilibrium must be less than0.7 and more then 0


Stable equilibrium will be more commonwhen intraspecific competition is stronger than interspecific competition

Meta-analysis

Meta-analysis: combining results from amany experiments, deals with quantitative estimates and sums those over allstudies, very valid way of surveying literature




Meta-analysis of intra- vs. interspecificcompetition: effective size d = (xe –xc)/s




Meta-analysis of interspecificcompetition:


Calculate an effective size: difference invariable (abundance, biomass, etc.) in the experimental treatment and variable(abundance, biomass, etc.) of the control plots, divided by standard deviation(variation)


If the mean effect size is greater then 0,interspecific competition is more prominent

Does interspecific competition limit distribution?

Species have opposite patterns


consistent (provides some evidence)with idea that interspecific competition for some resource could be thelimiting factor of species ranges


however other factors must be considered

What is a community and how do we quantify community structure?

Working definition of community: A groupof interacting species


Species in a community can interact inmany ways: e.g. competition, predation, facilitation, mutualism


A community is made of many populations

Species richness?

Number of species occupying a given area


Scale dependent, therefore can only use tocompare areas of similar size


Estimate is dependent on intensity ofsampling (some species are harder to find)


As the number of samples increases, rarespecies are found, Need to make sure you have sampled enough to reach plateau


In most communities most species haveintermediate abundance THOUGH there is variation


If you log transform abundance can resultin symmetrical bell curve


Eveness: similar abundances


Rank abundance curve! Assume good sampling. Steep slope low eveness. Shallow slope high eveness.

How do communities change over time?

Ecological succession: changes in speciescomposition of a community over time. Primarysuccession. Primary succession after the total removal of all organic matter. Orat sites that have never been modified by organisms. Secondary succession begins afterdisturbance removes some of the organic matter Forest fire. Earthquakes.Hurricanes. Floods. Abandoned Farmland.

Mechanisms of ecological succession (3)?

Facilitation as a mechanism of succession Environmentchanged by residents. Less suitable for themselves. More suitable for new species. Disturbance > pioneer community > intermediatecommunity > climax community: Can eventually replace and facilitate itself. early successional species modify the environment so that it becomesless suitable for themselves and more suitable for later successional species




Inhibition as a mechanism of succession. Early occupants modify the environment toprevent establishment of other species. Early occupants can be replaced by manydifferent species, but over time longer-lived species prevail. Sequence of succession is unpredictable,with many possible end stages. species that first establish in an area modify the environment to makeit unsuitable for all other species




Tolerance as a mechanism of succession. Species survive by tolerating conditionsand out-competing others Climax species arethose that are tolerant of the environmental conditions early in succession. Species that are tolerant of the environmental conditions early insuccession dominate later successional stages

How do trophic interactions regulate communities?

Sometimes trophic interactions have hugeeffects and sometimes very little. Top-down:regulated by the abundance of predators is also a more recent idea then bottomup. Trophic downgrading: the idea that killingoff the predators has boom in herbivories thus degrading environment




Foodchains: not all interactions are equally important – some have larger effectthan others on structure of community

Hypothesis: Strong top-down interactionsstabilize communities

Predators keep prey populations belowcarrying capacity Because prey populations are below their carrying capacity,competing prey species are more likely to coexist More coexistence = higherspecies richness




Asymmetricalcompetition: there is a dominant competitor and a weaker competitor




Bob Paine (1960s): Predicted that if thestarfish Pisaster was removed, species richness within the rocky intertidalwould decrease

What stabilizes communities?

Keystone species (such as Pisaster) influencecommunities more than would be expected given their abundance


Sea star wasting syndrome is currently causing amassive die-off of Pisaster. Species richness declined: When Pisaster wasremoved, Mytilus colonized most of the available habitat, competitivelyexcluding other species. Evidence that top-down interactions stabilizecommunities

Defining stability (5)

1. Resistance


2. Return time


3. Resilience


4. Persistence


5. Constancy