Modelling populations 1 Flashcards
Model
representation of an idea, mathematical, physical, or concept
ecological model
a formalized conceptualization of an ecological concept
most often quantitative
BIDE
birth, immigration–> increase population
death, emigration–> decrease pop
Birth
and what constitutes as it
any process that produces new individuals in a population
ie. eggs laid, offspring borne, seeds produced, number of spores (sexual)
shoots produced, cell division, mycelial growth (asexual)
immigration and emigration are the main mechanisms of
dispersal
sessile organisms
depend on dispersal vectors
abiotic: wind, water (currents)
biotic: birds, mammals etc
non sessile organisms
move freely or take advantage of dispersal vectors
abiotic:wind, water(currents)
biotic: insects, transported in bird feathers
N(t+1) =
population size in the future, time +1
Nt =
pop size at time ‘t’
B =
number of births
I =
number of immigrants
E =
number of emmigrants
D=
number of deaths
if B+I > E+D
population grows
If B+I < E+D
pop decrease
what type of values to better compare trends in birth
Relative
ie per capita
what do the lower case bide mean
it means they are per capita
density dependent factors
what are they usually controlled by?
birth and death rate changes as the pop changes
typically as density increases pop growth decreases
biotic factors
ie paracites
Density independent factors
what are they normally controlled by?
-birth and death rate not varying with pop size,
-birth and death independent of the number of individuals in the pop
-controlled by abiotic factors
ie windstorm
How do we estimate the rates of change in a population
life table and fecundity schedule
fecundity schedule
table of birthrates for females of diff ages in pop
Net Reproductive rate
R0
average number of offspring produced by female individual in her lifetime
Generation time
T
average age in pop where female gives birth
can be greater than age of first reproduction if female reproduces more than once
Per capita rate of increase
what is it equal to
r
per capita birth rate minus per capita death rate
equal to b-d
x
age(days)
nx
number surviving to day x
lx
proportion surviving to day x
mx
average number of offspring per individual during time interval
what is the sum of lx*mx
R0
average # of offspring per individual
R = 1
each mother produces exactly one female offspring to replace the mother
population stable
R = 2.4177
each mother produces 2.4177 offspring to replace her
r < 0
b<d
pop declining
r=0
b=d
stable pop
r > 0
b>d
pop increase
