Topic 15 Flashcards
Exponential model of population growth is based on several assumptions about the environment which are.
- assumes that essential resources, space, food, are all unlimited
- assumes constant environment w no seasonality or variations or change of any kind
In real world environment isn’t constant and resources almost always become..
limiting if population numbers reach large sizes. b and d rate will change, and r value will change
Assume population is growing exponentially ..
- resources are initially high
- higher density demand for resources
- resource consumption eventually exceeds rate of resupply
- shrinking resources and unequal distribution of resources (increase morality and fewer offspring/individual)
Due to density-dependence, we should expect ..
r (=b-d) to vary with N (assumption of exponential model is that r is constant)
K=
carrying capacity, population size (N) that the environment can carry or support
Carrying capacity
max number of individuals an environment can support indefinitely. resources not unlimited
When N=K, r=0
population is not decreasing just at as much as it can hold
K acts as an..
equilibrium around which a population will fluctuate .
Population below K
increase
Population above K
decrease
Determining K is difficult as it will not necessarily ..
remain the same over time
From equation for exponential growth we can do math to arrive at an equation that incorporates ..
K
Logistic growth equation
∆N/∆T = rN(1-N/K)
As the population reaches the carrying capacity the rate of growth stop and if the population exceeds the K the population growth becomes..
negative
(1- N/K) is a correction factors added to the
exponential growth model
