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BSC 201 Exam 3
Terms in this set (64)
group of actually or potentially interacting species in the same location. Bound together by a shared environment and a network of influence each species has on the other
Species Richness (S)
number of species
Species Evenness (E)
*maximal when all species equal
How do species richness (S) and species evenness (E) contribute to diversity?
includes number and abundances of species
E + S
What do dominance-diversity plots show?
rank abundance plot and species-abundance distributions
* plots species (ranked by their abundance) and their abundance
species sequentially take a fraction of available resources
Ex.) British dinner table
Log Series distribution
a few dominant species but most species have low abundance
Ex.) well groomed lawn; grass is abundant with a few other species in low abundance
few species very common, few extremely rare, most intermediate
Broken stick model
Everyone gets the same amount of resources
Explain the difference between alpha, beta, and gamma diversity.
Alpha: within a local habitat unit
Beta: between habitat units
Gamma: total global diversity of all habitats
Stating the effects on the two species (harm, neutral, benefit), what are the five nonneutral
possible categories of two species interactions?
1.) competition (-,-)
2.) Mutualism (+,+)
3.) Predation/Parasitism (+,-)
4.) Commensalism (0,+)
5.) Amensalism (0,-)
between members of different species
Ex.) bunnies and lettuce
among members of one species
lion eats an antelope
*tapeworm living inside of a human
oxpecker and a zebra
barnacles on a whale
release of chemical toxins by plants that can inhibit the growth of other plant species
What is the difference between a fundamental niche and a realized niche?
Fundamental niche is where a species can exist and realized it where it actually exists
*affected by interactions with other species (predation, parasitism, competition)
What are distribution patterns of organisms that are suggestive of strong interspecific
patterns of realized niches suggest underlying competition
Why are experiments needed to conclusively demonstrate interspecific competition?
Such an experiment would typically have treatments removing one species, adding more
of one species, and a control. What are the predictions for the second species based on
the hypothesis of interspecific competition? Give two examples of such experiments
discussed in class.
outside forces could be affected the populations in unseen ways
*removing one species: predict increase in second species
*add a species: predict a decrease in competitor
2.) kangaroo rats(large removed), pocket mice, and deer mice --> smaller seed eating rodents increase and insectivorous species did not change in number
Lotka-Volterra competition equations
What do the parameters in equations mean?
intra-specific competition: (k1-N1)/k1
Interspecific competition: N1
Why is a competition coefficient used?
competition may be asymmetrical
*effect of species 1 on species 2 may not be the same vice versa
If interspecific < intraspecific competition, and vice versa, what values will the
competition coefficient take?
*Competition coefficient < 1
interspecific < intraspecific competition
*Competition coefficient > 1
interspecific > intraspecific competition
Why are we interested in the model equilibrium?LVCM
to determine if there is coexistence between the two species or if one drives the others to extinction
What will be the equilibrium points?
Joint Equilibrium: neither species' numbers changing
What are zero-growth isoclines on a phase plane diagram?
line that represents all of the combinations of species 1 and 2 that result in one species having a growth rate of zero
*aka null clines
Plot and describe in words and mathematically based on inequalities the basis of
the four possible outcomes of the Lotka-Volterra competition model.
1.) Species 1 always wins: species 1 line to the right of species 2 line (lines don't cross means one specie will drive the other to extinction)
2.) Species 2 always wins: sp2 to the right of sp1
3.) Unstable equilibrium: carrying capacities are furthest away from the origin; which species persists is undetermined
4.) Stable equilibrium: stable coexistence
When will there be stable coexistence based on the Lotka-Volterra competition
*α12 < 1 (intraspecific competition stronger for species 1 than interspecific competition)
*α21 < 1 (intraspecific competition stronger for species 2 than interspecific competition)
How does the outcome of the Lotka-Volterra competition model relate to the idea of
niche shows how species use resources
*more interspecific competition leads to greater niche overlap
*more intraspecific competition leads to less niche overlap
How does Gause's Paramecium experiment show the principles of competitive exclusion
and competitive coexistence, and the links to niche overlap?
when interspecific competition is high (niche overlap) then exclusion occurs
*when 2 species have the same niche, the stronger competitor will eliminate the other
Approximately how often, when tested, is the hypothesis of inter-specific competition
upheld, how often is the competition asymmetric? (Based on Connell and Schoener
What effect will competitive exclusion have on the community properties of richness
reduce species richness (S) and evenness (E)
Using the example of Connell's barnacles (lecture and simutext Barnacle Zone) explain
how environment and competition can shape species distributions.
Specie A will go high and Specie B will go low when competing for land
*specie B will go high and low when not competing
What is resource partitioning, and how can it be achieved?
when species divide a niche in order to avoid competition
*different species of warblers occupy different levels of niche within a tree and as a result evolve to better live in their new niche
Explain the difference between a niche shift (plastic) and character displacement
plastic is not an evolutionary change; takes place within generation
Explain with the use of the Galapagos finch example character displacement, and what the predictions are for traits of species living in sympatry and allopatry.
evolutionary change for resource division
Ex.) beak size, feet circumference
*sympatry: living together
*allopatry: living apart
*hot and dry conditions kills mosquito eggs
What do exploitative interactions mean for the per capita population change (dN/Ndt)
of exploiter and victim populations, respectively?
dN/Ndt of consumer increased at expense of prey (dN/Ndt prey decreased in presence of consumer)
What do the parameters mean?
Nprey= size of prey population
Npredator= size of predator population
How do prey grow in the absence of predators?
grow exponentially (without limit)
Which part of the predator equation relates to predator death, which part to predator
mNpredator= predator death rate
abNpreyNpredator= predator birth
What term defines the zero-growth isocline of prey? Or above what number of
predators will the prey population no longer grow?
Plot predator and prey zero-growth isoclines on a phase plane diagram and for each quadrant draw arrows of how the populations will change and describe why.
1. predator scarce, prey abundant: both increase
2. both abundant: predator increase and prey decreases
3. predator abundant, prey scarce: both decrease
4. both scarce: predator decrease, prey increases
What does it mean when we say the predator-prey oscillations are neutrally
stable, and what will perturbing the system do?
oscillations remain constant and predictable
*altering either the prey or predator populations will directly affect the other
How does the starting point on the phase plane diagram determine the amplitude of
if started farther away, then amplitude of cycle is simply greater
Adding prey self-limitation (a carrying capacity) leads to what change in the
reduce to stable populations below carrying capacity
What type of functional response (relationship between prey number and prey consumption) is in the classical Lotka-Volterra model?
How does predator efficiency influence predator-prey dynamics, system
stability and hence coexistence in more realistic models? Draw each of the four
phase plane diagrams with zero-growth isoclines. Alongside each, sketch on a plot
the densities of predators and prey.
1.) inefficient predator: prey at carry capacity
2.)Intermediate efficiency predator #1: stable coexistence (unstable oscillations)
3.) Intermediate efficiency predator #2: stable coexistence (stable oscillations)
4.) Highly efficient predator: predator drives prey to extinction (expanding oscillations then extinction)
Which five factors covered in the lecture will likely promote stability and
coexistence in more realistic models?
1.) predation not too efficient
2.) density dependent self-limiting affecting predators and prey
3.) predators do not switch between prey (monophagous)
4.) prey can survive in unfavorable conditions (refugia)
5.) reduced time lags between predator and prey population responses
How are prey refuges predicted to influence predator-prey dynamics?
promote coexistence by allowing a certain proportion to escape predation
Explain the difference between the terms mutualism and symbiosis.
Symbiosis: close, long-term interaction between two different species
mutualism: both benefit from interaction
What are the differences between facultative and obligate mutualists?
Obligate: the interaction is required for survival and/or reproduction
Facultative: interaction, though beneficial, is not absolutely required
What are the
differences between generalist and specialist mutualists?
generalist: able to thrive in a wide variety of environmental conditions
specialist: thrives only in a narrow range of environmental conditions or has a limited diet.
Reciprocal evolutionary change in interacting species
Use the Arbuscular Mychorrhizal (AM) and plant example to explain how mutualism
and parasitism are extremes on a continuum, how mutualism is about a balance of
costs and benefits, and how it can be context dependent.
fungi penetrates cell wall and plant provides with carbohydrates and fungi provides water and P
*obligate for fungus
*facultative for plant
What are indirect effects? Explain interaction chain indirect effects and interaction
modification indirect effects.
Indirect effects: effect of one species on another, mediated by a third species
*A affects C
Using an example of the sea star explain the concept of a keystone predator.
competitive exclusion in asymmetric competition prevented when dominant competitor is preferred prey
*limitation of prey species B by predator A, facilitates C
Triangle: A affects C
What is a trophic cascade?
effects produced 2 or more trophic levels down from top predator
What is the difference between apparent competition and direct interspecific
increase in B leads to decrease in species C because of increase of shared predator A
triangle: B - affects C
How important are indirect effects? Discuss.
varies, but can be important
*difficult to assess strength
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