Population Dynamics and Growth Flashcards
Population
group of individuals of a single species inhabiting a specific area
Characteristics of a Population [[6]
- Number of individuals
- Density
- Age Distribution
- Growth rates
- Distribution
- Abundance
3 Main Methods of Estimation of Patterns of Survival
- Cohort Life Tables [identify individuals born at the same time/cohort and follow from age 0 until death]
- Static Life Table [# of individuals per age class at that moment of time; snapshot]
- Age Distribution
Mortality vs Morbidity
Mortality: Death
Morbidity: Infection/sickness
Population Survivorship curves
TYPE I: high mortality among older individuals
TYPE II: constant mortality rate
TYPE III: high mortality among juveniles
Population Survivorship Curves X and Y axis
X-axis: Age
Y-axis: # of individuals
Survivorship rate
lx = nx / n0
Mortality
dx = nx - n(x+1)
DIEx
Mortality rate
qx = dx / lx
“quit rate”
Average # alive in age class
Lx = nx + nx+1 / 2
What is the significance of the Age distribution of a population?[4]
- History of Survival
- History of Reproduction
- Potential for future growth
- Stable vs Declining populations
_____ & _____ studied ______ [birds] to demonstrate dynamic population in a variable climate
Grant, Grant, Galapagos Finches
What factors determine rate of population change?
- Fecundity
- Birth & Death rates
- Net Reproductive rate
- Generation time
- Per capita rate of increase
Fecundity
mx = # of female offspring of each female
Net Reproductive Rate R0
R0 = Summation of [lxmx]
If R0 < 1 = declining
Generation time T
Summation of (x lx mx) / R0
Per capita rate of increase r
r = lnR0/T
How does dispersal influence local population density?
- Climate change
- Prey and Predator Dispersal
- Immigration and emigration
Formula for continuous population growth with unlimited resources
dN/dt = (rmax N)
dN/dt = rate of population increase
rmax = maximum per capita rate of increase
t = number of time intervals
Formula for size at any time of an EXPONENTIALLY GROWING POPULATION*
Nt = N0e^rt
Formula for a GEOMETRIC growth curve
Nt = N0(lambda)^t
lambda = geometric rate of increase
Differences between geometric growth and exponential growth
- Geometric growth measures in intervals, exponential growth measures continuously
- The appearance of geometric growth isn’t consistent unlike exponential; can appear jagged
Logistic Population Growth & Formula
- resources are limiting
- sigmoidal growth curve
- carrying capacity K
dN/dT = rmax N (1 - [N/K])
so as N nears K, population growth decreases
N/K = environmental resistance to population growth
5 assumptions of logistic population growth
- Linear relationship between population density and rate of increase [inverse]
- Instantaneous effect of density on rate of increase
- Constancy of environment and K
- Equal reproduction of all individuals
- Absence of emigration and immigration
What limits population growth?
- Density-dependent factors [biotic] e.g. disease predation and parasitism –> K selection
- Density-independent factors
[abiotic] e.g. floods temperature extremes –> r selection
Grant and Grant documented 5 ways that finches utilize cacti:
- Open flower buds in dry season to eat pollen [FOOD]
- Consume nectar and pollen from mature flowers [FOOD]
- Eat seed coating [aril] [FOOD]
- Eat seeds
- Eat insects from rotting cactus pads
Main source of food for cactus finches
opuntia helleri
Large organisms
_____ r
_____ population variability
Low
Low
