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Ecology 320 Exam 2


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What does the X colomn stand for in life tables?
Age Class
What does the Nx column stand for in life tables?
Number of survivors at the beginning of each age class.
What does Ix stand for in the life tables? What axis is it on a graph?
Proportion o forganisms surviving to start age class interval, x Formula: Nx/Ni Normally plotted on the y-axis.
Describe the Survivorship I curve
organisms live out their full physiological lifetime Ex: humans
Describe the Survivorship II curve
rate of mortality is fairly constant across age groups least common type
Describe the Survivorship III curve
organisms experience high mortality early in life Ex: tabpoles
What does dx stand for on a life properties table?
Number of organisms dying during age interval x to x+1
What is dx (of the life properties table) expressed as?
A proportion of initial population Formula: Ni/dx
What does the Qx (from the life properties table) stand for?
Gives the age specific morality rate Fromula: dx/Nx
What is Lx from the life properties table?
Average number of total years lived during age interval x to x+1 Formula: (Nx+N(x+1))/2
Wat does Tx (from the life properties table) stand for?
It shows the numbers of years left to live T1 = sum of Lx Tx = T(x-1)-L(x-1)
What does ex (in the life properties table) stand for?
Average life expectancy for individuals at the start of an age interval, x. Formula: Tx/Nx
What is a cohort or dynamic life table?
constructed by following a cohort of individuals, a group of individuals born within a given time span
What is a Time-specific, or static, life table?
sampling the population and obtaining a distribution of age classes during a specific period of time Assumes: 1) Each age class is sampled in proportion to its number in the population 2) Birth and death rates are constant 3) Population is stationary
What is a dynamic-composite?
similar to cohort approach, but it constructs a cohort from a composite of a number of individuals sampled over a period of years rather than just one birth period
What is a Fecundity table?
It involves the reproductive rates of a population.
What is mx (in a life properties table)?
It is the average number of daughters produced by a mother of a given age (x)
How is the net reproductive rate calculated? What is the symbol?
Symbol: Ro Formula: sum of (lx*mx) lx = proportion of oganisms surviving to start age class interval, x mx = average # of daughters prduced by mother of given age (x)
What it Ro?
It is the average number of female offspring produced during the lifetime of a newborn female. Formula: sum of (lx*mx)
What is Sx (in the life properties table)?
It is the survival rate. Formula: 1-qx
What is necessary to construct an age structure over time?
1) Initial age structure of population 2)Age specific survivor rate 3) Age specific birth rate Result: ability to predict the population for any time in the future
What is the Finite Multiplication Rule?
What is age distribution?
Overtime, this begins to converge with a lot in the younger ages...LOOK UP BOOK DEFINITION
What is stable age distribution?
constant proportion of individuals in the various age classes of a population - occurs in years 7 & 8 - can occur while population is still growing
What is stationary age distribution?
A special form of stable age distribution in which the population has reached a constant size with birth and death rates equal. - the lambda is 1
What is the Geometric Population Growth?
- plotted to see what the density looks like over time - stable age distribution; constant lambda - Needed: initial # of population & lambda
What is the finite multiplication rate for?
It can be used to estimate a continuous or instantaeous per capita rate of growth
What is Intrinsic Rate of Increase?
it is the continous or instantaneous per capita rate of growth, r
What is the equation for the Intrinsic Rate of Increase?
r = ln(lambda)
How do you go from discrete to continuous equations?
r = ln(lambda) e^r = lambda Nt = N0 * e^(rt) - Graph the Nt equation to create an exponential curve with no discrete points
What is the slope for an exponential model of population growth?
dN/dt = rNt For which Nt = N0 * e^(rt) is the integrated form
What is K?
K is the carrying capacity or population density that can be sustained given the availability of resources in the environment.
What is the rate of population growth equation with K included?
dN/dt = (rN)((K-N)/K)
What are the relationships between N and K?
- When the population size (N) is near zero, (K-N)/K is close to 1.0 and the population grows exponentially - as N approaches K, (K-N)/K approaches 0.0 and the population ceases to grow
What occurs from predatory?
- Effects on predator and prey populations - Functional and numerical response of predators - Prey responses
What occurs from herbivory?
Ecological evolutionary responses
What are "true" predators?
They are lethal - cause death.
What are parasitoids? Are they lethal?
Yes, they are ultimately lethal. They survive on prey, until prey dies and parasitoids moves onto another prey
What are parasites? Are they lethal?
They are (sub)lethal. Their objective is not to kill prey because it is needed to survive.
What are grazers? Are they lethal?
They are generally not lethal. They are seed predators.
Each predator prey relationship changes the others population. What is the equation for the rate of change for a prey population?
It is the (birth rate) - (death rate) dNprey/dt = rNprey - C*Npred*Nprey - C is the predation rate; efficiency of search and attack - Nprey = prey population density - Npred = predator population density r = intrinsic rate of growth
What is the prey growth rate equal to?
Prey birth rate
What does C stand for?
It is the predation rate. - how efficienct the predators are at searching for the prey - how efficient the predators are at attacking for the prey
What is predation rate the same as? What is the corresponding assumption?
It is the same as death rate. Assumption: all deaths are caused by the predators.
Each predator prey relationship changes the others population. What is the rate of change of a predator population?
dNpred/dt = B(C*Npred*Nprey)-D*Npred - Nprey = prey pop. density -Npred = pred. pop. density - D = death rate of predators - B = efficiency of pred. converting food consumed into offspring - C = efficiency of search and attack
In the rate of change for a predator, what does B stand for?
(number of prey killed) * (efficiency of predators)
How do you calculate the zero net growth isoclines?
We want to set dN/dt to zero to show no growth Follow equation algebraically (for rate of change in prey/pred. pop. density) When # of predators = r/C, the prey is not growing When # of prey = D/(B*C) the predator population is not changing
What axis is the # of prey? # of predators?
# of prey is on the x-axis # of predators is on the y-axis
What occurs to the prey population when it is above the (r/C) line? when it is below?
Above: prey population is declining Below: prey population is increasing
What happens to the predator population when it is to the left of the (D/BC) line? when it is to the right?
Left: decreasing predator population Right: increasing predator population.
When there are a lot of predators, what are the effects?
1) the prey population declines 2) the predator population declines
What happens when the predator numbers decrease?
1) the prey numbers increase
What did Gause use for his experiments? What was the outcome?
His experiments used protoza. FINISH!!
What is functional response? What is the equation?
Implies that the individual predator consumes more prey as the prey population increases. C*NPred*Nprey
What is numerical response? What is the equation?
increased consumption of prey results in an increase in predator reproduction B (C Npred NPrey)
Describe the type 1 functional response.
It is linear because the predator always eats the same amount.
Describe the type 2 functional response.
# of prey killed increases, and then saturates - might imply that if prey increases, then why don’t predators increase? There is probably another limiting factor to the predator
Describe the type 3 functional response.
# of prey taken is low, maybe has to do with refugia, it then increases, and then the Type II saturation occurs - low prey densities = low prey kills - high prey densities = saturating prey kills
What is lag time?
It is the time it takes for the predator population to respond to the prey population.
What are some defense mechanisms in plants?
Structural defences (like thorns and tough decomposition) Chemical defenses
When are defenses seen in plants?
When there is a strong plant/herbivore interaction and slow rate of growth
How do grazers decide where to eat?
It depends on the nutritional content. They want to increase their nitrogen (N) uptake
What are prey coevolution responses?
Defenses: chemical and morphological Mimicry Satiation - plant/seed production -huge seed production may be a response to seed herbivory Behavioral
Please draw the Population Interaction table.
Competition: both negative Predation: +/- Parasitism: +/- Amensalism: -/0 Commensalism: +/0 Mutualism: +/+ Neutral: 0/0
What are the 2 assumptions of interspecific competition?
The 2 species coexist in time and space Shared resource is limiting resource
What is the outcome when plants are grown alone vs. together?
The competition changes the biomass...what else??
What is partitioning competition?
What is the logistic equation?
dN1/dt = rN1((K1-N1)/K1)
Each species ________ the availability of resources for the other. It ______ the population size.
a) decreases b) limits
What are the types of individuals?
genets (sexual), ramets (asexual), clone (group of ramets from one genet)
What is a metapopulation?
Separated populations of a species interconnected by dispersal of individuals among habitat patches in heterogeneous landscape
What are 3 ways of dispersion?
Uniform (intraspecific competition) Random (uniform environment) Clumped (habitat, reproduction)
Dispersion affects our ability to determine _____ through sampling.
What is community?
naturally occurring and interacting assemblage of species
What influence the community?
abiotic disturbance, climate, species interactions, resource availability, species effects
What is the dominance-diversity curve?
It is the plotting of the most abundant to the least abundant species, creating a decreasing slope.
What are Clement's (1916) views?
- competition yields distinct cut-offs - discrete, repeatable associations - species have co-evolved - functions as a unit
What are Gleason's (1926) views?
- diffuse boundaries between species - species respond independently to environmental tolerances - associations due to similar requirements - chance plays a role
What is species richness?
number of species
What is species evenness?
Number of individuals in a species
What is the "super-organism" view?
Clement's view
What is the "individualistic" view?
Gleason's view
Who is Whittacre and what did he do?
He bridged the gap between Clement and Gleason.
How do we describe the structure of a community?
Physical -Vertical - Horizontal Biological - species composition - numbers, mass, importance - diversity
What fators influence community structure?
- competition - predation - other interactions - dispersal, resource requirements
Describe the aquatic stratification.
Temperature: decreases with depth Light: decreases with depth Nutrients: increases with depth
What are terrestrial zones?
It is the vertical structure of light, made up by plants, effecting plant diversity
How does the vertical structure influence animal diversity?
The greater the number of layers, the greater the number of different species that can be supported.
What are patchwork landscapes?
Changes in: Slope, Aspect, Soil nutrients, Soil moisture, Light
What are two types of patchwork landscapes?
Edges: abrupt changes in landscape Ecotones: gradual transition between communities, where physical factors are not changing so abruptly, meaning animal types are not changing abruptly - tend to see higher diversity b/c they are a mix of communities on either side
Why do edges/ecotones have increased biodiversity?
Because this is where two communities meet
What is zoneation?
spatial changes in community structure
Competition may influence:
the presence, absence or dominance of a species (organization)
What effect does predation have?
It prevents dominating species
What is the cascading effect?
predator lowers the prey population, so the prey’s food population will increase
What are keystone species?
The are vital to an ecosystem. - many prey species would die out and biodiversity will decrease

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