Class #10 - Population Growth

Bio 301 - Principles of Ecology

Birth & Immigration does what to the population?

Increases the population size

Death & Emigration does wha to the population?

Decreases the population size

Closed Population

A population that does not experience immigration or emigration, meaning its size is only affected by birth and death rates.

Open Population

A population that experiences immigration and emigration, allowing its size to be influenced by both birth and death rates as well as the movement of individuals in and out.

When N(1), the equation is?

N(1) = N(0) + B - D + I - E

N(t+1)

represents the population size at the next time interval

N(t)

represents the population size at the current time interval

B

the number of births during a specific time period

D

the number of deaths during a specific time period

I

the number of immigrations during a specific time period

E

the number of emigrations during a specific time period

b

is the per capita birthrate

d

is the per capita deathrate

Per capita birthrate equation

b= B/N(t)

Per capita deathrate equation

d= D/N(t)

When N(x>1) the equation is…

N(t+1)= N(t) + b(N(t)) - d(N(t))

Geometric growth

Predicts changes in a population size in discrete intervals where brith and death are not continuous

Exponential Growth

As the change in time (delta t) approaches 0, the rate of change is instantaneous

what is ‘r’ ?

Instantaneous rate of population growth per capita.

When r=0?

birth = death (population size doesn’t change)

When r>0?

birth > death (population size increases exponentially)

When r<0?

births < deaths (populations decreases exponentially)

Positive Exponential growth occurs in…

Populations live in favorable environments and are at low populations densities These conditions are present during the process of colonization and establishment in new environments