Exam 2 Flashcards
What methods are used for estimating population size? When would you use each method?
Box plots: count all organisms in a given box/area. Good for sessile organisms
Line-transect: count all individuals seen on a given walking distance. Good for fast, widely scattered or hard to find species.
Capture, mark, recapture (Lincoln-Peterson model): collect initial sample, tag, release, recollect and use ratio of tagged and untagged to estimate population
What are the assumptions of the Lincoln-Peterson model? (4) What are the consequences of violations?
N=nM/x
- Marked and unmarked individuals are captured at random
- if marked individuals more likely to be caught, N will be underestimated - No birth or death between initial marking and recapture
- if birth and death happen, more individuals will be unmarked leading to an overestimate of N - No immigration or emigration
- immigration: new individuals entering pop–> overestimate of N
- emigration: individuals leaving population –> underestimate of N likely - Marks are persistent/cannot be overlooked
- if marks able to be undone will lead to less marked individuals–> overestimate of pop
Common patterns of dispersion (distribution)?
Random
Regular
Clumped
Causes of Random dispersion?
Neutral interactions between individuals
Causes of Regular dispersion?
Antagonistic interactions between individuals or local depletion of resources
Causes of Clumped dispersion?
Attraction between individuals or attraction of individuals to a common resource
Shrub dispersion changes with age/size example
Young shrubs: clumped dispersion due to seeds not dispersing far away, and at safe sites, and due to asexual reproduction
As shrubs get older dispersion becomes more regular as shrubs compete for resources in soil through root systems
What are the 7 types of rarity? (really 3 + combos)
- Restricted Geographic range
- Narrow habitat tolerance
- Small local population
- 1 & 2
- 1 & 3
- 2 & 3
- all three
When do you use exponential growth vs geometric growth?
Assumptions for both?
geometric: reproduction rate is constant, non-overlapping generations or discrete breeding seasons
exponential: continuous reproduction
Assumptions: environmental conditions are constant, all individuals reproduce and survive equally well or there is a stable age distribution
How is per capita rate of increase related to body size?
As body size increases, per capita rate of increase will decrease. This has to do with it taking more resources to create larger offspring and more resources needed per individual
Cohort analysis
Follow single group of animals all born at same time until their death. Useful for plants and sessile organisms
Static analysis
Look at survival and reproductive rates of individuals of each age group. Good for long living or relatively mobile species
Age Distribution
way of estimating age-specific survival and reproductive rates.
Calculate difference in proportion of individuals in each age class, assumes differences are due to differences in mortality
can help indicate if a population is shrinking or growing based on proportion young and old individuals
What are density-dependent factors?
food supply; places to live (burrows, etc); effects of predators (bison example), parasites, and diseases
What are density-independent factors?
temperature, precipitation, catastrophic events
Consequences of crowding
- less food
- aggravates social strife
- promotes spread disease
- attracts attention of predators
Survivorship curves (types I, II, and III)
type I: high survivorship for most of life then sharp decline (humans)
type II: near linear survivorship no matter age (some birds, fish, etc.)
type III: low/fast initial survivorships at young ages then slows later in age (MOST COMMON TYPE). seen in plants and smaller organisms
What do you need to estimate population growth rates from a life table?
You need to know the net reproductive rate across all age classes (Ro), the survivorship (lx), and fecundity (Fx)
r = ln(Ro)/T Ro = sum(lx*Fx) T = sum(x*lx*Fx)/Ro
What does r tell us about birth rates, death rates, and immigration or emigration?
r = births - deaths
What does r tell us about birth rates, death rates, and immigration or emigration?
r = births - deaths
What is the difference between Sx and lx?
Sx is the survivorship per age group (so the probability of survival from x to x + 1 : Nx+1/Nx
lx is the overall survivorship (the percent survival rate from age 0 to age x) : lx+1 = Sx*lx
What is the inflection point of the logistic growth model represent?
Population growth rate is highest here (K/2). Represents shift from higher growth rate to lower growth rate
How do dN/dt and r change as population size changes under logistic growth?
dN/dt: higher at population sizes below K/2, lower at population sizes above K/2
r:
Why does carrying capacity fluctuate?
In reality, death and birth rates fluctuate. Since K is pop size at which births = deaths, it fluctuates as well
Why does carrying capacity fluctuate?
In reality, death and birth rates fluctuate. Since K is pop size at which births = deaths, it fluctuates as well
What is the rescue effect?
If populations allow for immigration, if one population were to have gone extinct it can be replenished by another population thus “rescuing” it
What is delayed density dependence, and how does it influence population fluctuations?
The time it takes before the effect is felt by a generation: commonly number of individuals born is influenced by past population densities. This can result in lags/delays that cause fluctuations that go above and below carrying capacity
What are demographic stochasticity, environmental stochasticity, Allee effects, and how do they increase the likelihood of extinction for small populations?
demographic stochasticity: chance events related to survival and reproduction of individuals
- chances of all individuals dying or not reproducing higher for small populations (extinction)
- can also cause allee effects
environmental stochasticity: change in birth/death rates due to random environmental fluctuations
Allee effects: population rate decreases as population density decreases. Passenger pigeon example (breeding traits/hard to find mates)
- if other 2 types happen can lead to allee effects and have a spiraling effect
What genetic problems plague small population?
inbreeding, genetic drift and loss of heterozygosity (diversity): allows for recessive diseases/mutations to become more abundant (ex:// lion with sperm abnormalities after near extinction)
In what ways are the dynamics of metapopulations different from those of single populations?
Can survive extinction events due to immigration and emigration (extinction and colonization dynamics)
What is a ‘classic metapopulation’? How does this differ from a ‘core-satellite metapopulation’?
classic: all colonized patches are similar in size
core-satellite: one large “source” patch immigrates to smaller “sink” patches
What two factors have the greatest influence on the probability that a given suitable habitat patch will be occupied? Why?
Patch size and closeness to other occupied patches
What are non-equilibrium metapopulations, and why are they called that? What is their likely fate? Why?
When decreased (very minimal) interaction between patches. Likely fate is extinction events in individual patches or speciation due to loss of rescue effect
What are interference and exploitative (= resource) competition?
Interference is the allocation of resources due to direct aggressive competition (interference via chemicals = allelopathy/ hyenas and vultures)
Exploitative is the allocation of resources in which the use of the resource by an individual makes it no longer available (rock space for lichen/root space )
What is the competitive exclusion principle?
No 2 species can coexist if they occupy the same niche
What does it mean to describe a niche as an “n-dimensional hypervolume”?
That there are many factors that go into describing an organism’s niche so something that can start as a 2-dimensional mapping (foraging height vs prey length) can have many more dimensions added based on the number of factors (n) involved
What are fundamental and realized niches? Why might they differ for a given organism?
fundamental: hypothetical niche based on organisms adaptive ability to survive in a given environment
realized: actual niche in which an organism lives
They differ in that realized is often smaller due to factors such as competition, predation, parasitism, etc.
What is character displacement? How does this relate to the ‘ghost of competition past’?
Character displacement: natural selection favors species that do not need to compete. Can relate by showing there was past competition (ex:// super fast antelopes and galapagos finches)
How does character displacement relate to the competitive exclusion principle?
If two species are competing for a given niche, either one will be driven to extinction or they will differentiate in their niches (competitive exclusion principle: no two species can coexist within the same niche). The result of either of these would be a species that no longer needs to compete, thus leading to the observation of ‘character displacement’ where it seems like a species is favored because it does not have to compete.
What predictions do Lotka-Volterra models make for the outcome of interspecific competition?
species with greater areas of growth (area under K2(1) and K2(1)/beta(alpha) line) will out compete other species. = unstable equilibrium
species with no clear winner can exist in a stable equilibrium
What are the Lotka-Volterra models?
Given on test but use alpha and beta as conversion factors to tell how much of the carrying capacity of a species (1) is taken up by another species (2)
What factors might allow species to coexist even if they compete?
When alpha < K1/K2 < 1/beta
degree to which each species is limited by own carrying capacity (K1,K2) as well as effects on each other (alpha, beta)
If species have similar strong effects (alpha and beta: broad niche overlap) then carrying capacities must be almost equal for coexisitence
if species have similar weak effects (weak niche overlap), coexistence can occur even if K’s are very different
Why might the outcome of interspecific competition depend on environmental conditions?
Because different species may have better fitness with different abiotic conditions (temperature, humidity, etc)
What is apparent competition?
Looks like competition but is produced by indirect effects of predators
What are parasitoids?
parasite that develops in host and kills on way our
What are hyperparasitoids?
Secondary parasitoids that develop at expense of primary parasitoids
Why do internal vs external feeders typically have different diet breadths?
While internal feeders may have food more abundantly available the diversity of diet choice may be small where as external feeders may find it more difficult to find food but there may be a larger diversity in diet choice (?)
Why do predator-prey cycles arise?
From numerical and functional responses that cause fluctuations in population sizes
- predators eat prey: prey pop decreases
- predators starve: predator pop decreases
- few predators leads to increased prey pop
- increased prey leads to increased predator pop, completing the cycle
What factors influence the degree of fluctuations in predator-prey cycles?
predator reproduction rate, prey reproduction rate, environmental/adaptive factors (ability prey to hide/ability predators to hunt)
what conditions are necessary to get persistence of both predator and prey in the long term?
adaptations to avoid being eaten/ to hunt: coevolution
no extinction events
predator populations must be affected by decreased prey populations (?)
Under what conditions can predation lead to increased species diversity in a community?
Different strategies can be adapted to deal with predation
What is the difference between predator functional response and numerical response?
numerical: changes in the number of predators
functional: changes in the attack/consumption rates of predators on prey (types I, II, and III)
type I - liner (filter feeders)
type II - prey handling time leads to curve (wolves/moose)
type III - lower food intake at smaller prey densities then similar to type II (can be due to prey rarity)
What are two mechanisms responsible for the leveling off of rates of predation as prey populations increase in the Type II and III functional responses?
They are limited by handling time and satiation
Why do rates of predation initially increase slowly as prey populations increase in the Type III functional response?
Due to a lesser ability to search/handle prey at smaller densities (rarity)
ex:// kairomones can attract predators, some predators switch to most abundant prey species,
How do numerical and functional responses of predators relate to predator satiation?
Predators can only consume so much so as prey population increases past a certain point consumption rate will no longer increase
How does predation act as a selection force on prey life histories?
Guppy example: if a certain predator prefers to eat/hunt certain size of guppy, can influence size, age of fecundity, number of offspring produced, etc.
How might predation act as a selective force on prey coloration?
Lynx and hare example (ability to camouflage)
