Chapter 9 Population Growth Flashcards
Per capita rates of birth and death
- constants for a population
- can be used to predict growth rate of the population regardless of N(t)
Instantaneous per capita growth rate
(b-d)… prolly shoulld look through 174-175
Exponential model of population growth
dN/dt = rN
If r is greater than 0,
population size is increasing exponentially
if r is 0
population size is contant
if r is less than 0
populaation size is decreasing exponentially
Cohort
group of individuals born in the same period of time
Cohort life table vs Dynamic Composite Life Table vs Time-Specific Life Time
Cohort/dynamic life table: fate of a group of individuals is followed from birth to death
Dynamic composite life table: constructs a cohort born over several time periods instead of just one… like following a group from 1955, 1966, 1957
Time Specific Life Table: doesn’t involve a group but is constructed by sampling the population in some manner to obtain a distribution of age classes during a SINGLE time period
lx calculation
survivorship: l2 = n2/n0
l5 = n5/n0
qx calculation
age specific mortality rate
where d0 = n0-n1
q0: d0/n0
where d3 = n3-n2
q3: d3/n3
Survivorship curve is based on what value? Mortality curve?
Survivorship = lx mortality = qx
3 Types of Survivorship curves
Type I: Human, high survivorship for a long time then hits a point drops fast to low survivorship
Type 2: Consistently decreasing survivorship… linear… common with birds and rodents
Type 3: Trees, quickly decreasing survivorship at the beginning, then evens out and steadily decreases after a point
How to calculate sx
age specific survivorship rate:
1-qx
Fecundity measurement on lifetables?
age specific birth rate… number of births per age
Gross reproductive rate
Sum of all age specific birth rates of the population… sum up all the bx
Ro
Net Reproductive Rate
-sum up all the lxbx values to come up with this! more accurate as it accounts of survivorship!
If Ro is less than 1? Equal to 1? More than 1?
Less than one: not replacing selves, shrinking pop
Equal to one: replacing exactly themselves
More than one: more than replacing self, adding females
Calculation of (upside down y)
upside down y of t = 1 is N(1)/N(0)
upside down y of t = 5 is
N(5)/N(4)
important concept
For r-Selection your B and D will both be very high, and for K-Selection both B and D will be low. However, both will result in a positive λ simply because it’s all about the ratios.
Stable age distribution
when the PROPORTIONS of each age group in the population remain the same year after year… even while the population continues to increase
Stationary age distribution
a special form of stable age distribution in
which the population has reached a constant
size with birth and death rates equal…. no more growth in population, and same proportions still!!!
Relationship between r and lamda (upside down y)?
r = ln(lambda)
and
lambda = e^(r)
