Population growth

Question 1

dN
—— =
dt

Answer 1

Change in N
———————– =
Change in time

Question 2

Reasons for population change

Answer 2

Deaths, births, emigration and immigration

Question 3

Exponential growth model

Answer 3

dN
—– = rN
dt
N is pop size, t is time, d is change in something

Question 4

How to calculate slope of growth

Answer 4

by multiplying the population size (N) by a constant r, so increases as the pop grows.
R is the per individual (per capita)rate of population increase and can be different for each for each population.

Question 5

Logistic population growth model

Answer 5

dN
—— =rN (K-N)
dt ——-
K
Growth slows at higher N, until it levels out at a maximum ‘carrying capacity’ (K) of the environment
K = maximum sustainable pop size

Question 6

density dependance

Answer 6

Growth slows down at higher densities
Implication: birth rate, death rate, migration rate change with pop density

Question 7

Mechanisms of density dependence

Answer 7

Intra-specific competition for resources
The higher the pop density the fewer resources on average per individual

Question 8

Disease transmission

Answer 8

High density > more contacts > high transmission
Eg respiratory diseases Tuberculosis
but less so for sexually transmitted diseases