Modelling Pop Growth Flashcards
What is exponential growth
Unlimited growth of a population
Observed during initial colonization of unoccupied habitat.
Assumes closed population with no immigration or emigration
How to calc population growth rate
Birth rate - death rate = population growth rate
b - d = R
What’s doubling time.
Doubling time of a population is the time required for it to reach twice it’s current size given the current rate increase.
Species with higher r value have shorter doubling times
What does the logistic growth model describe
The effect of increasing density on population growth.
What happens as species density increases:
Competition for resources increase
Birth rate decrease
Death rate increase
Population growth slows down
What is logistic growth
Density dependent model - rate of population growth slows down as population size increases.
More realistic model of population growth over long time period.
Assumes closed population with no immigration and emigration.
When N = K
Population growth stops
What is stochasticity
When the values of r and k vary from year to year as birth and death rates fluctuate in response to environmental conditions.
Carrying capacity can also vary.
What is a stochastic model
In a stochastic model there are multiple outcomes, each has certain probability of occurrence.
Each parameter can vary around a specified mean.
Model is run multiple times to generate a set of outcomes.
Why do we incorporate variability in population models.
To increase realism of our population model we incorporate variability in the parameters.
This is informed by data from our population.
What population projections can be included to incorporate variability in a population model.
A margin of error to reflect natural variability.
Different projections for different scenarios.
What do population growth models describe.
They describe mathematically how population size changes over time.
Applications of logistic growth model:
Setting maximum sustainable yield reference points in fisheries management.
