older sheep are susceptible to
predators due to less agility—adults steeply die
off later in life; this is also true for humans!
Type 2:
individuals in a population with type 2 die at
equal rates, regardless of age; the slope is a constant
which suggests that the mortality is constant over time
—each class has same probability of dying
o
Birds:
(the sparrow and robin): you see steady
decline in survivorship overtime until they are all
gone by age 6; Ground finches
o
Mud turtle
Type 3:
individuals showing type 3 die at a high rate as
juveniles and then at much lower rates later in life—an
example would be the sea turtles (loggerhead)
o
Desert shrub:
after out of seedling stage, there
are very little shrubs left. Then at about 30 years
old they have high survivorship until the end
o
Darwin’s Ground Finch (ex of life table): display type 2 survivorship
First 3 bullets points on slide 31 would be given info on
test
L0 could be subbed for 1
2.
AgeSpecific Fecundity:
o
Fecundity = reproductive capability and is age
dependent
o
Potential fecundity: ignores survivorship
o
Net Reproductive Rate (R0)
: expected # of
female offspring produced per female
per
generation
o
Complete Life Table
o
Generation Time (T):
mean period of time
elapsing between birth of parents and all
offspring
T=
average across all families within the
population
The larger the organism, the longer the
generation time and vice versa

Predicting Population Growth
o
R0
= expected number of female offspring produced per female per
generation (
net replacement rate);
it is the multiplicative growth per
generation

R0 is an indicator of growth
R0=1
no change; the mother is replacing herself
exactly once in her lifetime, so the population will not
grow
R0 > 1
increase
R0 < 1
decrease

N(t+1) = NtR0

If R0=2, the population would double each generation, known
as
geometric growth.
o
Predicting population size at any time in the future:

Lx and bx do not change over time

Scotch pine, black noddy, global human population: examples
of J shaped curve (exponential)
o
Modeling Accelerating Growth

NonOverlapping Generations:
No age structure
Annual species
Exhibit
geometric growth
: Nt = NoRo^t

Overlapping Generations:
Age structure
Exhibit
exponential growth
: Nt = Noe^rt
o
r
= intrinsic rate of increase, per capita rate of
exponential growth. The bigger the r the steeper
the curve.
o
r determines rate of increase; r is also max rate
of population growth (r
max
)
r < 0
exponential decline
r = 0
stable
r > 0
exponential increase
r = ln(R0)

T
o
Intrinsic rate of increase (r) declines predictably
with increasing size
Finite rate of percapita growth: lambda
o
r is constant through time:
No change in vital rates
No change in biotic interactions
No major change in weather
o
There are no limiting resources (unlimited
resources)
o
The growth rate of population (r) doesn’t depend
on age structure (in the long term)
The bigger your size, the longer your generation time
and vice versa
R0 is multiplicative growth per generation, also known
as geometric growth
We do we assume when predicting population size? Lx
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 Summer '08
 Brown,D
 Ecology, Demography, Population Ecology