EE Lecture 25: Intro Population Ecology Flashcards
what is the fundamental eqt of population dynamics
Nt+1 = Nt + Bt - Dt + It - Et)
what is eqt for exponential growth
dN/dt = rN
what are the limitations for the exponential growth eqt
only occurs with no competition/predators and excess resources
what does the r stand for in the exponential growth eqt
r = intrinsic rate of natural growth (b-d)
define limiting factor
syop pops increasing exponentially by reducing growth rate
define regulating factor
the subset of limiting factors that bring pops back to eqb,
what are the two sides to regulating factors
doesnt only limit pops also makes them recover when rare
how many types of survivorship curves are there
3
Type 1 - most individuals survive until old age
II-individuals have a constant chance of dying throughout their lives
III-most individuals die young
give examples of density dependent processes
disease
predators
lack of space
what is value of lamda for all pops under favourable condns
what does this lead to
lamda > 1
leads to exponential growth
give examples of density independent processes
floods
hurricanes
temp
precipitation
are floods density (in)dependent processes?
density INDEP
is food a density (in)dependent process
density DEP
what does a density independent factor mean
their effects on birth and death rates are independent of the number of individuals in the popn
how do you know a factor is density INDEPENDENTq
because they dont tend to increase the pop size when small and dont decrease pop size when large
what does density dependent mean
a factor that consistently leads to changes in popn growth as a function of density causing BR and DR and dispersal rates to change
when is popn regulation said to occurq
when one or more density dep factors cause pop size to increase when numbers are low and decrease when numbers are high
name some density dep factors
food
space
resources
what effect do regulation factors have on lamda and r
tend to increase lamda and r when pop is small
decrease lamda/r when pop is big
which factors can regulate pop size
only density dep factors
name some pops where density dep has been bserved
song sparrow - the number of eggs laid per female decreased with density, as did the number of young that survived long enoughh to become indep of their parents
give an example of density dependent mortality
highest initial planting densities of soya beans meant most of them died.
eggs of the flour beetle placed in glass tubes - death rate increased as density of eggs per tube increased
what happens to a pop if lamda = 1
pop stops growing
what type of density (in)dependence do flour beetles show
show density dependence
as egg density increases, death rate increases
what is the logistic eqt of popn ecology
dN/dt = rN ( 1- [N/K])
what does the term [1-(N/K)] in the logistic eqt represent
reresents the net effect of factors that reduce the pop growth rate from the constant (r) rate as seen in exponential growth
compare logistic growth to exponential growth when densities are low
logistic growth is similar to, but slightly lower than exponential growth when densities are low
when densities are low, why is logistic growth similar to, but slightly lower than exponential growth
because when N is small the term (1-N/K) is close to one, and hence a pop that grows logistically, grows at a rate close to r
at what point does logistic growth level off
eventually a pop that grows logistically levels off at the carrying capacity = K
