# Lecture 9: Populations: Population growth & regulation Flashcards

per-capita phenomenon

Population growth via births and deaths

Total population growth

the individual reproductive rate multiplied

by the population size

the bigger the population size, what gets greater?

the numerical growth

what is an appropriate and convenient way to view growth?

in discrete time steps (generations, years)

when counting a population when should they be taken and why?

it needs to be taken at the same time each time step, to be sure that the same birth and death cycles are included

Geometric growth

- Growth via discrete time steps
- Population size is a function of starting population size, per capita growth factor, and number of time steps
- lines on the graph do not represent anything, data is only present on the dots

geometric growth formula

Nt = (N0)(λ^t)

explain the variables in the geometric growth formula

- N = Number of individuals
- λ (lambda) = Geometric growth factor
- t = Number of discrete time steps.

what is the geometric growth factor (λ)

- it is a multiplier
- ratio of population size/population size the previous year

what happens to organisms with a continuous growth?

they reproduce and die at a relatively steady rate at all times

what is exponential growth

-Growth (positive or negative) at a continuous rate that is a proportion of the total number of individuals at any given time.

-Population size is a function of starting population size, the growth rate, and the time that has elapsed

- lines on the graph represent the data

exponential growth formula

Nt = (N0)(e^rt)

explain the variables for the exponential growth formula

- r = Exponential growth rate.
- e = the exponential constant.
- N = Number of individuals
- t = Time elapsed.

what is e^r in the exponential growth formula replacing and why

- it replaces λ
- to describe that all individuals have a chance of reproducing at any time, not just at a discrete time step

geometric growth (λ) - decreasing population size

- 0 < λ < 1
- λ is in between 0 and 1, not inclusive

geometric growth (λ) - constant population size

λ = 1

geometric growth (λ) - increasing population size

λ > 1