Flashcards in Fill in the blanks for lecture 5 Deck (44):
_______ and _________ increase population size (_), _______ and ___________ decrease population size.
Births and immigration increase population size (N), deaths and emigration decrease population size.
The geometric growth of a population has two assumptions:
1) A closed system
2) Population growth is continuous
In the geometric growth of a population equation,
N is ________ ________
r is -
t is ____
N- population density
r - per capita population growth rate
t - time
The _________ growth equation is given by dN/dT = rN.
The exponential growth model (single species) assumes what?
1) unlimited food and space to grow
2) No predators
3) Closed system (no immigration/emigration)
What is the integrated form of the exponential growth equation?
N(t) = No*e^(rt)
N(t) = population density at time t
No = initial population density
t = time
r = per capita population growth rate (intrinsic growth rate)
Assume you are rearing a population of insects in the lab. You start with 100 individuals and the intrinsic growth rate is 0.2 insects/week. Assume that growth is continuous.
What would the population of insects be in 6 weeks?
N(t) = No*e^(rt)
N(t) = 100*e^(0.2*6)
N(t) = 332
________ is also called the Verhulst model.
When comparing the prediction of Verhulst, using the first 5 U.S censuses, he predicted the population growth, and it was found to be?
Nearly identical to the actual census data.
Logistic population growth - As a population increases in size (increased density), its growth rate will decline due to:
1) Depletion of resource
2) Aggressive interactions among individuals (competition of resources)
3) Increased wastes
________ ________ is a negative feedback between density and per capita growth rate.
Logistic population growth assumes?
Closed system: no immigration/emigration
Density dependent per capita birth and death rate varies with ________ ______ (______).
Population size (density)
The carrying capacity K, is the point at which birth and death rate are _________.
logistic (or verhulst) single species model - growth in a ________ _________.
What is the equation for the logistic growth model, and what do each of the variable mean?
dN/dT = rN ((K - N)/K)
dN/dt = change in numbers/change in time
r - intrinsic rate of increase
K - carrying capacity
N - population size
Calculate the % growth for a population with:
K - 4 000
r = 0.1 individuals/year
N - 4 500
Thus, since N is larger than K, the % growth must be negative.
dN/dT = rN ((K-N)/K)
dN/dT = 0.1 * 4500 * ((4000-4500)/4000)
dN/dt = -56.25 individuals per year
Then, convert to percentage.
-56.25 individuals/year * 100%/4500 individuals
= -1.25% growth per year
Instead of getting a perfect fit of the logistic growth model in nature, we often get _________ around the carrying capacity.
The logistic growth equation predicts sigmoidal population growth through time. The population size (density) reaches a _______ maximum at K, __ _______ ________.
Stable maximum at K, the carrying capacity
Visualize how population growth rate (dN/dt) varies as a function of population size. The peark of the dN/dt corresponds to the _______ ____ in the dN/dt vs. time curve.
The inflexion point in the dN/dt vs. time curve corresponds to _/_ K.
dN/dt declines with _________ population size (N).
Assumptions of the logistic equation are _________.
The assumptions of the logistic growth model are: (4).
2) no Oscillations/time lags.
3) External environments has no effect on dN/dt,
4) if an individual can reproduce, there is no size or age effect
The assumption of a closed system in the logistic growth model lends itself to a _______ ________.
The assumption of no time lags means that the dN/dt responds _________ to changes in N. Why is this unrealistic?
Unrealistic since it takes to to catch up
The assumption that if an individual can reproduce, there are no size and age effects is unrealistic since?
Unrealistic for real populations. Generally morphology plays a role in differential reproductive success.
Field evidence for ______ ______ (typically done along a time scale).
When looking at a meta analysis of the rate of population change per generation (r(G)) (y-axis) vs. log(number of generations monitored) (x-axis), we see that as the number of generations increase we reach a point of _____ ___ ______.
Zero net growth
Alternative method for testing density dependence. Experimentally alter population sizes. Then measure: (3)
birth rate, death rate, population size
What factors are important in density dependent population regulation?
Top-down regulation: competition, predation
Bottom-up regulation: resources
_______ density dependence and Allee effects.
The allee effect is what?
Low densities associated with limited ability to find a mate.
Positive density dependence and allee effect.
At what rate do species return after local extinction by an exotic fish?
Recovery of zooplankton is achieved by resting eggs buried in silt.
Studied 4 alpine lakes where non-native trout were removed and _____ __ ______ _____ _____.
Looked at recovery over time
Daphnia has ________ reproduction.
Hesperodiaptomus has ______ reproduction.
_______ species may recover from 1 diapausing egg.
An increase in the abundance of 1 species is linked to the decrease in the abundance of another - _________ (_____-___) ________.
Compensatory (zero-sum) dynamics
Synthesizing 30 years of data from desert rodent community. Shift in vegetation from grasses to woody shrubs and a corresponding change in rodent community. Coexisting granivorous rodents using the ______ _________ _________.
same limiting resource
What was observed in the shift in rodent communities over 30 years, concerning the grassland and shrubland species.
Increase in shrubland species and decrease in grassland species - compensatory dynamics.
Despite the species turnover in the rodent study, species _______ has remained constant.
Temporal trends in granivorous rodents:
Average individual rodent body size _______ significantly over time.
Total rodent abundance _________ significantly over time.
Decline in metabolic rate due to drought, 1985-1995 but no overall change in resource consumption (energy flux). Therefore - ________ ___________.
The idea of compensatory (zero-sum) dynamics is controversial.
Argue that _____ ______ (______ and _______) are more important than ________ _________ in driving fluctuations in species abundances within communities.
Argue that abiotic factors (temperature and precipitation) are more important than competitive interactions in driving fluctuations in species abundances within communities.