Modelling Populations I Flashcards
What is a Model?
- formalized conceptualization of ecological processes
- usually, but not always quantitative
What is BIDE
- birth, immigration
- death, emigration
Birth
any process that produces new individuals in a population
- eggs laid, offspring born, seeds produces, etc.
Death
could be from old age, disease, lack of resources, herbivory, predation, etc.
Main Mechanism for Immigration and Emigration?
Dispersal: the permanant movement of individuals into or out of a local population
Why is modelling most often based on birth and death?
immigration and emigration are difficult to track, so they often assumed to be constant
Density-dependent Factors
- birth and death rates change as the density of the population changes
- typically as density increases population growth decreases
- usually controlled by biotic factors
Density-independent Factors
- birth and death rates do not vary with population density
- birth and death rates are independent of the number of individuals in the population
- usually controlled by abiotic factors
What is a Fecundity Schedule?
a tabulation of birthrates for females of different ages in a population
Ways to estimate the rates of change in a population
- life tables
- fecundity schedule
Parameters of Population Change:
- net reproductive rate
- generation time
- per capita rate of increase
Net productive rate
- average number of offspring produced by a female individual in her lifetime
- r-naught
Generation time
- (T)
- the average age within a population at which a female gives birth to her offspring
- can be greater than age of first reproduction if female reproduces more than once
Per Capita rate of Increase
- (r)
- equal to per capita birth rate minus per capita death rate
- b-d
Why do Scientists focus on fecundity in females
- because maternity is easier to track than paternity
