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Ecology CH. 10
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Gravity
Terms in this set (56)
What is a life table?
summary of age specific, survival probabilities, and fecundity rates.
_______ may determine reproductive rate, not age.
size. Especially important in plants, reptiles, many invertebrates & other species
where growth continues throughout life or when it is difficult to determine age
What are 2 ways in which life-specific survival and fecundity data can be collected and summarized?
1. Cohort life table
2. Static life table
Cohort
group of organisms born at the same time
Cohort life table
Best for short lived, sessile organisms.
Follow one cohort through out their lives.
Static life table
sample different cohorts during one time period.
Snapshot of entire population at one point in time.
must be able to age individuals or group into stages.
better for long lived or mobile organisms
In a cohort LT, it is_____ possible for older age classes to have higher ________ probabilities than younger ones.
NOT.
Survivorship.
But it could stay the same if no one dies.
Survivorship curve
a graph showing the proportion of individuals surviving at each age for a given specie or group
survivorship curves can differ among?
populations and cohorts
In a Cohort LT, what does a net reproductive rate that is >1 mean?
increase in population size
In a cohort LT, what does a net reproductive rate that is < 1 mean?
decrease in population size
In a cohort LT, what does a net reproductive rate that is = 1 mean?
No change in population size
A life table data can be used to project future what?
age structure, population size, population growth rate.
What does age structure influence?
population growth rate
what does a rapid growth rate chart look like?
wide on the bottom, narrow on top. (Guatemala, Nigeria, Saudi Arabia)
what does a negative growth rate chart look like?
wide on top, narrow on bottom. (Italy, Germany, Bulgaria)
what does a zero growth rate chart look like?
constant through al ages. (Spain, Greece, Austria)
If you know (1) ____ (2) ___ (3) ______
for a population you can predict how it will change in the future.
survival rate, fecundity rate, current age structure.
What 2 things do you need to predict future population size?
# surviving to the next time period and # of offspring the survivors produce in the next time period.
Stable age distribution
proportion in each class remains the same from year to year.
proportions in each age class ______ a lot for the 1st few years
fluctuates
Geometric population growth rate (lambda)
describes rate at which population size changes over a time period.
"growth" rate does not always mean?
N is getting bigger
the further lambda is from 1..?
the more rapidly the population is changing
what does it mean for lambda to be dimensionless?
it has no units
lambda is dimensionless but it must..?
record the time period over which it was calculated
lambda must be greater than?
zer0, but it has no upper limits
If you calculate lambda over several time periods, you will note that it _______ at first
fluctutates
After a few years, lambda will stabilize as the population reaches __________
stable age distribution
lambda characterizes population size changes between?
discrete generations (nonoverlapping)
If you want to know the population growth rate from a previous time period to now, then you need to know?
population size now and population size in the previous period
If you want to know population size in the next time period, then you need to know?
population size now and lambda
If you want to know population size in any future time period, then you need to know?
population size now and lambda
what is the difference between discrete and continuous population growth?
in discrete growth generations do not overlap, whereas in continuous growth they do overlap ( both are J shaped curves a.k.a growth in constant proportions)
lambda is dimensionless while r is?
not
if r=0, then?
0 offspring/individual born and thus growth = 0
if lambda =1 then?
Nt = Nt+1 thus no population growth
if r>0 then?
offspring are born and population size increases
if lambda >1 then?
Nt+1>Nt thus population size increases
if r<0, then?
more deaths than births so population size decreases
if lambda < 1, then?
Nt+1 < Nt thus population size decreases
Doubling time
time for present N to double in size
larger r ___ shorter T double
=
Populations can grow ______ when conditions are favored
exponentially
Can exponential growth continue indefinitely?
no
What 2 factors regulate population growth?
1. density dependent factors
2. density independent factors
density DEPENDENT population regulation
change in population size (N) causes changes in growth/ death rates. (intraspecific competition for resources)
density INDEPENDENT population regulation
changes in environment alter birth and death rates. irrespective of population size.
density dependence can be modeled by?
making a slight change to the exponential growth model (becomes a logistic model)
The closer N gets to the maximum, the?
slower the population growth rate
in a logistic model, population growth rate depends on?
proximity to K
in an exponential growth rate model, population growth always changes by?
a constant proportion
in exponential growth, what factors cause the population to stop increasing?
r=0
N=0
in logistic growth, what factors cause the population to stop increasing?
r=0
N=0
N=K
Logistic growth assumes that resources are ________ but if resources ______ changes then __ changes too
constant
availability
K
when is population growth at its maximum rate?
when N reaches 1/2 its max (a.k.a 1/2 of K)
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