Unit 3 Flashcards
- How do natural populations grow? What is exponential growth? How do we mathematically describe exponential growth? What is r? What is doubling time?
Geometrically, or following the discrete model for exponential growth dN/dt = rN r = intrinsic rate of growth doubling time (t) = the amount of time in which a population doubles = 0.693/r
Compare and contrast exponential and geometric growth (the discrete model of exponential growth)? What is lambda? How do the two models compare? How do lambda and r compare?
With exponential growth, populations grow continuously. With geometric growth, growth occurs over a discrete interval
Lambda = The ratio of population size in one year to that of preceding year (or other time interval)
They are identical except that lambda takes the place of er
Direct correspondence between r & lambda, except r is an instantaneous rate of increase and lambda is a finite rate of increase.
- What is logistic growth? What is density dependence? What is carrying capacity? What is the mathematical representation of logistic growth? Compare and contrast logistic growth with exponential growth. Where is the inflection point for the logistic growth curve? Where on the curve would you find the maximum sustainable yield (MSY)?
Logistic growth = Modified exponential growth equation to describe the effect of population density
density dependence = Any factor that becomes more significant in highly dense populations
Carrying capacity = maximum size of a population that a habitat can sustain
log vs exponential = The log equation dN/dt = rN [1- (N/K)] is identical to exponential growth, except that it includes the influence of a carrying capacity
inflection point = K/2
Where MSY = At half of the carrying capacity
- What factors influence intrinsic rates of increase (r or lambda)? What factors bring population growth under control? Compare and contrast density dependent and independent factors. What are Allee effects?
Death and birth rates
Density dependent factors: resource availability, spread of disease, predation
Dependent vs independent = The magnitude of the effect changes dependent of density or not
Allee effects have a positive relationship between density and growth
What is demography? What is a life table? What is the use of a life table? Compare and contrast age (cohort) and time specific (static) life tables. What is cohort analysis?
Demography - the study of growth, survival, and age structure in natural populations.
Life table use - Tool for characterizing a species’ by estimating the likelihood of mortality and reproduction change with age
cohort (age specific) vs static (time specific) life tables - cohort analysis follows one gen through life. Static takes a sample of the pop at a given point in time
What are the basic life table variables? How are they computed?
lx = nx/n0 = proportion of individuals surviving to this age bx = age specific fecundity = cannot be computed sx = rate of survival = 1- mx mx = mortality rate =[ nx- (nx+1)] / nx or dx/nx ex = age-specific life expectancy = sum of lx + future generations all over lx Ro = Net repro rate = sum of lxbx T = avg generation time = sumXlxbx / Ro
Can we approximate the exponential growth rate (r) from a life table? If so, how?
Yes, ra = lnRo / T
What is a growth pyramid for a population? What would the pyramid for an expansive population look like? A stationary? A constrictive?
A graphic representation of the age distribution of a species with the oldest individuals at the top
expansive - more abundant younger generations
stationary - even distribution among ages
constrictive - more abundant older generations
What is a survivorship curve? How do we generate these curves? What are the three general types of curves? What are some examples of organisms that fall into each type of curve? What factors might give rise to the three basic types of survivorship curves?
A graphic representation of mortality rate of a population through its lifespan, generated by life tables (cohort or static analysis)
Type I - most live to old age. Species that have large offspring and invest a lot into raising them
Type II - equal mortality rate through life. Bird, lizard species
Type III - High infant mortality, low mortality until old age. Octopus, squid, alligator
Size and quality of offspring, care bestowed by parents, predation patterns
- How do populations respond to variation in the environment? Is fluctuation in population number common for natural populations? Organisms with what values of r are more likely to “track” environmental fluctuation?
Different species respond differently
Yes, fluctuation is common
Organisms with r values >1 “track” environmental fluctuation
- What factors might cause some populations to show periodic cycles in population number? What is a time delay (time lag) in response to population density? What is the delay differential equation?
A time lag causes periodic cycling
Density dependent effects depend on past time (t-tau)
delay differential equation - dN/dt = rN [1- (Nt- tau / K)]
What is a monotonic return to carrying capacity? What are damped oscillations? Stable limit cycles? What values of r and τ give rise to these different responses?
Monotonic - normal logistic growth (0< rt<0.368) monotonic return
Damped osciallations - overshoot and undershoot equilibrium until stable (0.368r<1,6
Stable limit cycle 1.6
- How does a time lag factor into the discrete-time logistic model? What is a monotonic return to carrying capacity? What are damped oscillations? Stable limit cycles? Chaos? What values of r give rise to these different responses? How does the discrete-time delay model differ from the delay differential model?
Nt+1 = Nt + rNt (1- Nt/K) - has a built in time lag of length of 1.0
r < 1, -montonic return (normal logistic growth)
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What is the basic metapopulation model (mathematical)? What are stochastic factors? How are extinction probabilities affected by stochastic processes in small populations?
dp/dt= cp(1-p) – ep
e = probability of subpopulation going extinct p = fraction of suitable habitat patches occupied by subpopulations. c = rate of patch colonization
Stochastic events- random chance events (tornado, hurricane), have a stronger effect in small pops than large pops
- What are the different types of multi-species interactions?
- Neutral (0,0)
- Mutualism (+,+)
- Commensalism (+,0) shark and fish
- Amensalism (-,0) elephants tromping small animals
- Parasitism (+,-)
- Predation (+,-)
- Competition (-,-)
- What is predation? Compare and contrast it with other forms of multiple species interaction.
Predation (-,-) includes:
- Carnivory
- Herbivory - includes grazers, browsers and seed predators
- Parasitism- parasite doesn’t kill the host
- Parasitoidism- parasite lays larvae in host that end up killing the host
- Cannibalism- same species predation
Compare intimacy of relationship and probability of death
- What are the types of plant defenses against herbivory? What are chemical defenses? Compare and contrast quantitative and qualitative defenses? What is meant by an evolutionary “arms race”?
Types:
- Chemical defenses- plants produce chemicals poisonous to other organisms
- Mechanical- spines, thorns, spikes, trichomes
- Defensive association (ant plant)
- Failure to attract
- Masting (black brush) – large, irregular reproductive episode (mast year)
Quantitative- defenses that has a dose dependent effect (C based)
Qualitative- Chemical defenses that are very effective at a small dose (N based)
Herbivory theory- higher herbivory leads to more defenses, higher cost of defense lead to fewer defenses, most defenses are allocated to the most valuable tissues (leaves), environmental stress lessen the availability for defensive mechanisms
Arms race- herbivores and plants are in an evolutionary race to gain some advantage over the other
- What are the types of prey defenses against predators? What are the two forms of mimicry? Compare and contrast Batesian and Mullerian mimicry. What is crypsis? What is aposematism?
Types- mimicry, hiding, escaping, crypsis, warning coloration, chemical, structural and behavioral
crypsis- camouflage behavior
aposematism- warning coloration
two forms of mimicry:
Batesian- organisms that are not poisonous, but mimic things that are poisonous or otherwise harmful
Mullerian- All poisonous or harmful species mimic each other, convergent evolution
- How does parasitism differ from other forms of predation? How many host steps are typically involved in parasite life cycles? How does parasitism differ from parasitoidism? From the textbook reading, what are the mechanisms of parasite transmission? What is a vector? What is horizontal transmission? What is vertical transmission?
Parasitism- Organism has a close, long intimate relationship with host and lives in or on the host and doesn’t directly kill the host
Parasite life cycle host steps- Usually more than one. Maybe two or three
Mechanisms of transmission- vertical, horizontal
Vector- organism used to disperse parasite from one host to another
Horizontal transmission- movement between individuals other than parent and offspring
Vertical transmission- from parent to offspring
- Who was Charles Elton? Who are Lotka and Volterra? What is the Lotka-Volterra predator prey model? What are predator and prey zero-growth isoclines? What is meant by zero growth? Can you predict short-term dynamics of the predator/prey model? If so, How? How would you determine the period and amplitude of the predator/prey cycles? What is neutral stability? How does neutral stability or neutral equilibrium differ from a stable equilibrium?
Charles Elton- Ecologist that tracked pelts brought into Hudson’s Bay Company. Looked at links between predator and prey species (linx and snowshoe hair)
Lotka and Volterra- prey population: dR/dt =rR-cRP Where P = number of predators and R = number of prey (resource), c = capture efficiency of predation.
- It’s a modified exponential growth model. Assumes the only thing that limits prey growth is predation.
- Predator population: dP/dt = acRP-dP. Positive growth occurs when there are enough prey to eat, where d = natural mortality and a = the conversion efficiency of prey into new baby predators
- Assumptions:
o No immigration
o No age or genetic structure
o No time lags
o Growth of prey pop limited only by predation
o Predator dependent on one prey species
o Individual predators can consume infinite numbers of prey
o Random predator and prey encounters
Zero-growth isoclines- plot used to find the conditions in which we would see no growth for either predator or prey
Predators = r/c. Below the line, prey increases, above the line, they prey pop decreases
Prey = d/ac. Right on the line is zero growth. If below, predator declines, above, the predator increases
Zero growth- no growth in either prey or population model
Predict short term and how- Yes plot it in the zero-growth isocline and determine how each population is increasing/decreasing based on which quadrant its in
- Amplitude is determined by the initial population sizes
- Period of the cycle C = 2pie / √rd
is dependent on prey growth rate and predator death rate
neutral stability (equilibrium)- The point where the equilibrium isoclines for predator and prey cross.
differs from stable equilibrium- Conditions will naturally return to a stable equilibrium unless disturbed. In neutral stability, you won’t ever achieve equilibrium except by random chance
- What happens in the predator prey model if you add a carrying capacity to the prey? What is the relationship between b and K?
Adding carrying capacity- dR/dt = rR - cRP – bR^2
. Prey lines are not straight, but constrained. Instead of cycling continuously, the cycle ends at the joint equilibrium
Relationship between b and K- K = -bR^2
- What is a functional response? What is the difference between a Type I, II, and III functional response? Which functional response would you expect with the Lotka-Volterra predator prey model?
Functional response- Graphical representation of the proportion of prey consumed by a predator across prey densities
Type I- constant attack rate constant across all prey sizes (Lotka-Volterra model)
Type II – Takes into account handling time and satiation. Increase to a point, then leveling of
Type III – Takes into account depressed growth at low density due to prey being harder to capture/find at low density
- What is Holling’s disc equation? What is handling time? What is a numerical response? What are multiple steady states in predator/ prey models?
Holling’s disc equation- T = Ts+ThE, where Ts is search time and Th is handling time per item and E is the number of encounters.
E = aRT / 1 + aRTh
a is a constant for efficiency of searching and R is prey density. T is the time it takes a predator to catch and consume a prey
Handling time- total amount of time a predator spends feeding includes searching and handling time
Numerical response- The response in the number of predators to the number of prey
Multiple steady states- when plotting isoclines using Holling’s equation, there are 3 possible equilibria: unstable equilibrium, neutral stability, stable equilibrium
- What is competition? What is intraspecific competition? Interspecific competition? Diffuse competition? Exploitative competition? Interference competition?
Competition- Any use or defense of resource that reduces the availability of that resource to other individuals
Intraspecific competition- competition within a species
Interspecific- competition between species
Diffuse competition- Many species competing for the same resource
Exploitative competition- species use the same resource, such as food. The use by one reduces the availability for another
Interference competition- direct interaction between competitors in which one interferes with or denies access of another
- What is a resource? Nonrenewable resource? Renewable resource? What is Liebig’s law of the minimum? What is synergism?
Resource- any substance or factor consumed by an organism and supports increased population growth
- Consumed
- uses resource for its own maintenance
- When availability is reduced, growth is reduced
Nonrenewable- resources not regenerated
- Space is a nonrenewable resource. Once occupied, it is unavailable
Renewable- resources regenerated
- Animal food and soil nutrients for plants
Liebig’s law of the minimum- Law that states that the potential of a resource to limit a pop depends on availability relative to demand
- Each pop increases until supply of the limiting resource becomes depleted
- Law applies strictly to resources that do not interact to determine pop growth rate, independent influence
Synergism- When two or more resources interact to determine the growth rate of a consumer population
- When two resources together promote growth more than either individually
- What is the mathematical model by Lotka and Volterra for interspecific (2 species competition)? How is the logistic model altered to take into account this competition? What is the competition coefficient? Using this model when would you predict species 1 to exclude species 2; when would you predict species 2 to exclude species 1; when would you predict competition to go either way? When coexistence of the two species?
Mathematical model- dN/dt=rN[1-(N/K)]
Logarithmic altered how- added competition term alpha Ni/Ki
- dN1 / dt = r1N1[(K1-N1-alpha12N2) / K1]
o Separate equation for each species
o In the absence of interspecific competition, you have normal logarithmic growth to carrying capacity
competition coefficient- alpha12 is the degree to which sp. 2 uses the resources of species 1
- alpha 21 (beta) is the degree to which species 1 uses the resources of species 2
When would sp. 1 exclude sp. 2- when sp. 1 isocline is higher than sp. 2
when 2 exclude 1- when sp. 2 isocline is higher than sp. 1
when go either way- When the isoclines cross
When coexistence- same as could go either way but with stable equilibrium point
- What is the competitive exclusion principle of Gause? What types of factors can affect the outcome of competition?
Gause’s principle- Complete competitors cannot exist. Two competing species with identical ecological requirements cannot occupy the same area
- Assumes:
- Genetically unchanged
- No immigration of losing species
- Environmental conditions remain constant
What types of factors- Abiotic conditions, disturbances, predation and herbivory
- What is apparent competition?
APPARENT COMPETITION- INTERACTIONS BETWEEN COMPETING SPECIES THAT ARE MEDIATED BY CONSUMERS (GARLIC MUSTARD’S DOMINANCE RESULT OF HERBIVORY)
ASYMMETRIC COMPETITION- ONE SPECIES MAY HAVE A NEGATIVE EFFECT ON ANOTHER AND NOT VISA VERSA
- What are mutualisms? What is meant by obligate vs. facultative mutualisms? What is a symbiotic mutualism?
MUTUALISMS- INTERACTIONS BETWEEN SPECIES THAT BENEFIT BOTH PARTICIPANTS
- CAN FORM TO COEVOLUTION
- LICHENS (ALGAE OR CYANOBACTERIA+FUNGUS)
OBLIGATE- REQUIRE EACH OTHER TO PERSIST
FACULATIVE- INTERACTION IS NOT CRITICAL TO SURVIVE
SYMBIOTIC MUTUALISM- CLOSE TIGHT RELATIONSHIP
GENERALIST- SPECIES THAT INTERACTS WITH MANY OTHER SPECIES IN A MUTUALISTIC WAY
SPECIALIST- A SPECIES THAT INTERACTS WITH ONE OTHER SPECIES (OR FEW CLOSELY RELATED) IN A MUTUALISTIC WAY
- What is a community? Compare and contrast the main views of communities? Who were the main voices on each side of the debate? What studies were responsible for the settlement of the debate?
Community- a group of populations of two or more species occupying the same area at the same time
Main views of communities-
o Organismic (holistic) – Clements
community like a superorganism (loss of one organism means loss of community
o Individualistic – Gleason
Environment determines where species are found
Who were the main voices on each side- Clements and Gleason
What studies settled the debate?
- Many today take an intermediate view
- What is an open vs. closed community? What are ecotones? Where do you typically find ecotones?
open community- diffuse boundaries, ranges independent of eachother, uncommon and diffuse coevolution, individualistic organization
closed community- holistic organization, distinct boundaries (ecotones), coincidental ranges (coinciding), prominent coevolution
ecotones- sharp, distinct boundaries of species
where do you find ecotones? - Along an environmental gradient
- What is the continuum concept? What is gradient analysis?
continuum concept- Along a continuum you have varying abundance of species
gradient analysis- looking at abundance of species across some environmental gradient (ex. moisture)
- How do we measure heterogeneity of a community? What is species richness and how is it calculated? What is species diversity? How does it differ from richness and how is diversity calculated? What are MacArthur and Shannon-Wiener indices of diversity? How do MacArthur’s and Shannon-Wiener’s indices compare? Under what situations would one be preferred over the other? What is meant by the evenness of a community and how is it computed?
MEASURE HETEROGENEITY- THROUGH SPECIES RICHNESS, DIVERSITY AND EVENNESS
DOMINANCE = AREA COVERAGE OF SPECIES (PLANT) OR BIOMASS
RELATIVE DOMINANCE- AREA COVERAGE RELATIVE TO OTHER SPECIES
RELATIVE DENSITY= TOTAL INDIVIDUALS OUT OF ALL INDIVIDUALS
FREQUENCY = FREQUENCY OF ENCOUNTERING SPECIES AT SPECIFIC INTERVAL (SAMPLE PLOT OR POINTS)
SPECIES RICHNESS, HOW CALC.- NUMERICAL COUNT OF NUMBER OF SPECIES
SPECIES DIVERSITY- NUMBER OF EQUALLY ABUNDANT SPECIES
MACARTHER INDICES- D = 1 / SUMP^2
- GIVES NUMBER OF EQUALLY ABUNDANT SPECIES
SHANNON-WEINER INDICES- H = -SUMPNATURALLOGP
- MORE COMMONLY USED
- GIVES MORE WEIGHT TO RARE SPECIES
- WITH MANY RARE SPECIES, USE SHANNON-WEINER
WHEN WOULD ONE BE PREFERRED- SEE ABOVE
EVENNESS OF A COMMUNITY, HOW CALC (J)- DIVIDE THE ACTUAL SPECIES DIVERSITY OF THE COMMUNITY BY THE MAXIMUM POSSIBLE DIVERSITY OF THE COMMUNITY
O J = D/DMAX, WHERE DMAX = S
- What is the J-shaped species abundance pattern? What is meant by stability in a community? What is meant by the diversity stability hypothesis? How does the study by David Tilman support the diversity-stability link?
J-shaped pattern- frequency class plotted against number of species. Most species are rare in a community; There are a few dominant species
stability-
- 1. Resistance to change
- 2. resilience – ability to come back after change
diversity stability hypothesis- the hypothesis that higher diversity means greater stability
David Tilman study- biomass ratio in prairie before and after a drought. Supported the diversity stability hypothesis
- How do we classify communities? What are some of the statistical methods used to determine community delineation?
How classify communities – Delineation of communities can be difficult unless the transition between adjacent communities is abrupt (ecotone)
- Often arbitrary
methods to determine community delineation –
- Ordination – (see slides)
- Cluster analysis – cluster groups by similarity
- How do we define spatial variation in community structure? How do we define temporal variation in community structure?
define spatial variation – zonation
define temporal variation – succession
- What is succession in communities? What is a sere? What is a seral stage? Define the two basic types of succession (primary vs. secondary)?
Succession – change in community structure in time
Sere – a successional sequence
Seral stage – A stage in a successional sequence
Primary – starting from scratch (no soil or seeds) ex glacial recession, lava
Secondary – Remnants are still there (soil, seeds) after disturbance. Ex sea grass
- What drives succession? What are the models that have been proposed to explain how succession is driven in communities? How do they differ?
What drives succession –
- Facilitation
- Inhibition
- tolerance
What are the models proposed –
Facilitation – embodies Clement’s view – each stage paves the way for the next. Early colonizers pave the way for future species
Inhibition – the presence of one species prevents another from establishing. When inhibition is acting, succession moves forward only through the death and replacement of established individuals. Favors longer-living individuals
Tolerance – a species can invade a new habitat and become established independently of the presence of other species. Early stages are dominated by poor competitors that are good toleraters.
Null hypothesis – random colonization and random extinction causing turnover and change in species over time
- What are the characteristics of pioneer and climax species? How do they differ? If you consider both Clementsian and Gleasonian seres, would you expect a single climax community or alternative climax communities?
Characteristics of pioneer species – wind dispersed, many small seeds, stuck to animals, long see viability, low root : shoot, rapid growth, small size, low shade tolerance
Characteristics of climax species – eaten by animals, large seed size, few seeds, short seed viability, high root : shoot, slow growth, large size, high shade tolerance
Clements view – one climax community
Gleason view – potentially have alternate “climax” communities
- What is the state and transition model for succession?
SOME DISTURBANCE STARTS THE PROGRESSION, TRANSITIONS FROM ONE STAGE TO THE NEXT
DISTURBANCE OVER A THRESHOLD PRODUCES AN ALTERNATE CLIMATE STATE
- What is a shifting mosaic on the landscape level?
SMALL SCALE DISTURBANCES OPEN GAPS THAT ALLOW FOR SECONDARY SUCCESSION. BEST PROMOTES (ANIMAL) SPECIES DIVERSITY
