Chapter 10 - Population Growth and Regulation Flashcards
Provides a summary of how survival and reproductive rates vary with the organism’s age.
Life Table
Components of a Life Table
Nx = number of individuals alive at a given age x (or age range) within a span of time.
Sx = survival rate. Chance that an individual will survive to the next age (x + 1).
lx = survivorship. Proportion of individuals that survive from birth (age 0) to age x.
Fx = fecundity. Number of offspring produced by a female at age x.
Records the fate of a group that was born at the same time and is observed from birth to death usually for observing shorter life spans
Cohort Life table
Analyzes the fate of a group from estimated ages or an already existing record of a particular period or time usually for observing loner life spans
Static Life Table
Uses lx (Survivorship) to plot the number of individuals in a hypothetical cohort (transformed to 1000 individuals) that will survive to reach different ages. Varies among species and may also vary in interspecies populations or among cohorts .
Survivorship curve
Three types of survivorship curves
Type I - Death rate increases as they reach old age
Type II - Near-constant trend, almost linear
Type III - High death rate among young with few survivors
The category or specified age range, where everyone in a population may belong to
Age class
Summary of proportion of the population that belong to a set of age ranges
Age structure
How to calculate predicted no. of individuals surviving to the next period (ex. breeding cycle seasons)
Predicted no. of individuals surviving to the next period = nx * Sx
Where: nx = no. of individuals in an age class
Sx = survival rate of the age class.
How to calculate the number of newborns the survivors will produce in the next period. (applies to fertile age range with recorded offspring).
= (average # of offspring of an age range * # of individuals of that age range)+…
The ratio of the population in one time point and the previous. “How fast did the population increase/decrease within that time span.
Population Growth Rate
Population growth rate (λ) = Nt+1 / Nt
Populations grow at fixed rates when?
Age-specific birth and death rates are constant over time
The point when the age structure of a population does not increase nor decrease from one time point to another.
Stable age distribution
T/F Populations can grow indefinitely exponentially when conditions are favorable.
Populations can grow exponentially when conditions are favorable. But not indefinitely.
Two related patterns of population growth, helping in rapid increase of population size:
Geometric growth
Exponential growth
Population grow geometrically when?
This applies to organisms that have a synchronous reproductive time
Reproduction occurs at regular time intervals
Refers to the regular intervals of reproduction
Discrete time period
This growth is characterized when population changes in size by a constant proportion from one discrete time period to another
Geometric Growth
Population with continuous reproduction changes in size by a constant proportion in each instant in time, J-shaped curve
Exponential Growth
Formula to find the population size at t generations for geometric growth
Nt= λ^t / N0
Where Nt is the population size after t generations
N0 is the Initial Population size
And λ is the geometric growth/ratio
How to solve for population size at each instant of time for Exponential growth
dN/dT = rN
N(t) = N(0)e^(rt)
where:
N(t) is the population at time t
N(0) is the starting population
dN/dT is the rate of change in population size
r = constant rate of increase
N = Current population size
e = Euler’s Number = 2.718
Number of years a population will take to double in size
Doubling time (td) = ln(2)/r
where R is the exponential growth rate
Mean number of offspring produced by an individual during its lifetime.
Net Reproductive Rate (R0)
= summation of (lx * Fx) from x_first to x_last
where
x = age
xfirst = age of first reproduction
xlast = age of last reproduction
lx = survivorship
Fx = fecundity
Cause birth rates, death rates, or dispersal rates to change as the population density changes
Density Dependent Factors
