Population Growth

Age pyramids
– a wide base is indicative of a population growth in the future
– developing countries have pyramid shaped graphs
– developed countries have straighter graphs (no population growth = population will stay the same)
Population Growth Models (key)
Nt – pop at time t
No – original pop size
B – # of births
D – # of deaths
I – immigration
E – emigration
? – geometric growth rate, replacement rate or (N(t+1))/Nt
r – intrinsic rate of natural increase or B-D per individual
k – carrying capacity
General Growth Model
Nt = No + B – D
Geometric Growth Model
Nt = No?^t

-discrete breeding
-non-overlapping generations

Exponential Growth Model
dN/dt = rN

-continuous breeding
-overlapping generations
-unlimited environment
J-shaped curve

Logistic Growth Model
dN/dt = rN (K-N /K)

-continuous breeding
-overlapping generations
-limited resources
S-shaped curve

intraspecific competition
competition for resources w/in your own specie