Population growth Flashcards
what results in population growth?
reproduction
Population size is the
number of individuals alive at a particular place
population size is influenced by
birth, death, immigration, emigration (individual leaves and becomes part of new population)
B is
Births
D is
deaths
per capita birth rate (b) equation is
B/N
per capita death rate (d) equation is
D/N
per capita growth rate (r) equation is
b-d, or r= (B-D)/N0
the change in total number of individuals in a population equation is
B-D
we can use per capita growth rate to
predict population size
if r>0
population is growing
if r<0
population is shrinking
the Exponential model of population growth (as time increase, population increase) tells us:
The per capita growth rate (r) will be
at a maximum (rmax) for that population (always increasing)
rmax is always positive in this graph
what is Rmax
the intrinsic rate of increase (rate of increase if there were unlimited resources)
in bacteria, Rmax is
10
in mammals (large), Rmax is
0.001
Bigger organisms have ____ rmax
less
Smaller organisms: _____ rmax
greater
what affects generation time and rmax?
Time before sexual maturity
Gestation time
Lifespan
the size of the population growing exponentially is given by
Nt, where they give the times
What limits population growth
Predation
Limited food
Limited shelter
Disease
Abiotic Environment: temp, precipitation
Carrying Capacity is given by
K
what is carrying Capacity
the max population size that the environment can hold, given by K
what determines the growth rate (r )
how close the population size (N) is to the carrying capacity (K)
r changes with N in the
logistic population growth graph
Population size symbol is:
N
in the N vs r logistic population growth graph, as N _____, growth rate ______
increases
decreases
in the N vs r logistic population growth graph when N=K…..
r=0
in the N vs r logistic population growth graph when N>K….
r<0 (population is shrinkng)
in the time vs N logistic population growth graph….r is ______
and _____ as individuals ______
r is the slope
r decreases as individuals increase
rt is the _____
rate of increase at a certain time
in the time vs N logistic population growth graph, K is _______
the asymptote
factors that influence Population growth have an increasing effect as _________
N becomes large
Biotic factors that affect population growth (density dependent):
competition for food,
shelter,
predation,
access to mates,
disease
Crowding (density- dependent) influences:
reproduction
growth rate
adult size
survival
ex. as there is more seed density, there is less seed productivity
as there is more plants, there’s is less growth in plant
as there is more birds, the probability of them surviving is zero
Abiotic factor that influence population growth (density independent):
Temp
Precipitation
Disturbances (fires, floods)
Density independent factor have affect at:
any population size
R-selected species are/have :
small body size
in environments where disturbance is common
High growth rate
Low survivorship
Semelparous : big reproduction all at once
Short lifespan
High fecundity
K-selected species are/have:
iteroparous
large size
long lifespan
later reproduction
slower growth rates
