Examining population change Flashcards
U5L2 (16 cards)
What’s carrying capacity?
The maximum population an ecosystem can sustain due to resources.
What’s Fecundity?
The potential number of offspring a species can produce in its lifetime
What’s survivorship?
The pattern exhibited by the average age of death within a species.
What are three types of survivorships?
Type I: Initially low mortality rates, most individuals reach reproductive age.
Type II: Mortality rate is at a constant rate from birth to old age.
Type III: Mortality rate is highest for young offspring; most do not reach reproductive age.
What is the original population change equation?
Pop. Change = [(births + immigration)] - [(deaths + emigration)]/initial population size * 100
What is the new population change equation?
In most use cases, we do not care about immigration/emigration, because of this, the new formula is:
b = B/N
b = birth rate
B = births
N = initial population size
What is the formula for death rate?
d = D/N
‘D’ replaces ‘B’ cuz it corresponds to number of deaths.
What is the intrinsic birth rate of a population?
(r) is the difference between these two values.
r = b - d
If r > 0; population increase
If r < 0; population decrease
The instantaneous growth rate changes overtime as the population grows.
What is the formula for the instantaneous growth rate of a population?
dN/dt = rN
dN/dt = instantaneous growth rate
r = intrinsic growth rate
N = population number
the change in size of population overtime depends on the growth rate of said population
What does growth look like in ideal conditions?
Growth in ideal conditions. No factors to limit the growth of a population.
The highest r value can be reached which is why growth is exponential in this case.
An example of this is bacteria is a good environment
What is the formula for exponential doubling time?
td = 0.69/r
What about population growth in limited environments?
If populations are allowed to grow exponentially, there reaches a point where the environment can no longer support the number of individuals. Eventually, the population is forced to stop growing.
b = d, r = 0 at this point.
What is carrying capacity?
Carrying capacity is the point where the population stops growing. This is called the carrying capacity of the environment (K).
This is the maximum population that can be sustained by the environment over a long period of time.
What is the formula for carrying capacity?
dN/dt = rmaxN (K - N)/K
K = carrying capacity
N = instantaneous population
rmax = maximum possible growth rate
As N approaches K, K-N approaches zero and growth slows to a stop.
What is geometric growth rate?
In species where birth rates occur at set intervals, (coinciding with matin season).
We see spikes in seasonal births & few/no births at other times of the year.
These population follow a GEOMETRIC growth model.
What is the formula for geometric growth?
A = N (t + 1)/ N(t)
A = population growth rate observed each season
N(t) = population in a given season
N(t+1) = population the following season
