Lecture 16 Flashcards
(17 cards)
ecological models
describe ecological processes, simplified version of the world that experiments (thought or physical) can be done with
population model
birth, immigration, death, emigration –> population size
birth
any process that brings new individuals into a population via reproduction - different meanings depending on type of organism
immigration and emigration
populations interact with each other, some rates of individuals being exchanged
death
could be from old age, disease, lack of resources, predation
modelling population growth equation
Nt+1 = Nt + B + I – D – E
population growth or decrease
If [B+1] > [D+E] the population grows
If [B+1] < [D+E] the population decreases
per capita
for each individual
per capita population change
Nt+1 = Nt + Nt(b + i – d – e)
density-dependent factors
rate influenced by population density (ex: competitors, predators, disease)
density-independent factors
rate does not vary with population density (ex: floods, extreme temperatures)
measuring rates of population change
using a life table and a fecundity schedule it is possible to estimate the rates of change in a population
fecundity schedule
a tabulation of birth rates for females of different ages in a population (only track females, but sex ratios are almost always 1:1)
net reproductive rate (N0)
average number of of offspring produced by an individual in a population
geometric rate of increase (lambda)
the ratio of the population size at two points in time
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 birthrate minus per capita death rate, or more simply, B-D
