Lecture 9: Regulated Population Growth Flashcards
Exponential population growth is where
populations grow continuously and generations overlap
- keeps growing, does not level off
- the intrinsic rate is unaffected
dN/dt = rN
Geometric population growth is where
populations grow in discrete time intervals and reproduce synchronously
N t+1 = Lambda(Nt)
When lambda is less than 1 and r is less than 0 the population size ____
the population size decreases in size (lambda < 1 r < 0)
When lambda is more than 1 and r are is more than 0 the population size ____
the population size increases in size
When lambda or r are equal to 0 the population size ____
stay the same or do not change
Can real populations grow exponentially? When?
YES:
- colonization of new habitats
- recovery after catastrophe
- pulse of new nutrients
- introduced species
all can cause populations to grow exponentially
what does r affect in exponential growth –> dN/dt = rN
how rapidly population size increases. r is constant, it is not affected by N
Exponential growth ___ be sustained for long periods of time in a population
CANNOT
the logistic population growth model shows us…
what determines K (carrying capacity)?
the per capita rate of population growth approaches zero as the population size nears carrying capacity (K)
- K can be determined by various limiting factors such as space available, food available, etc.
What is the equation for the logistic growth model
dN/dt=rN ((K-N)/K)
K-N shows us the number of additional individuals the environment can support
(K-N)/K is the fraction of K that is still available for population growth
r selection is …
is selection for life history traits that maximize reproductive success at low density (further from carrying capacity)
k selection is …
is selection for life history traits that are advantageous at high population densities (closer to carrying capacity)
define density independent populations
populations where birth rate and death rate DO NOT CHANGE with population density
define density dependent populations
birth rates and death rates directly or indirectly regulated by population density
density independent factors
effects on birth and death rates independent of number of individuals (weather conditions, catastrophes,)
density dependent factors
birth, death, dispersal rates change as the density of the population changes (disease, predation, malnutrition)
positive vs negative density dependence
positive density dependence is where population growth is facilitated by increased population density.
negative density dependence is where population growth is facilitated by decreased population density.
define density dependent mortality
density dependent birth and death rates are an example of negative feedback that regulates population growth.
What are the mechanisms of density dependent populations regulation
- Competition for resources
- Disease
compeition for resources
increasing population density intensifies competition for resources resulting in lower birth rate
disease
In dense populations, pathogens can spread more rapidly
