Chapter 9
logistic growth equation:
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Geometric growth rate (λ)
A constant porportion by which a population of a species with discrete reproduction changes in size from one discrete time period to the next. AKA Finite rate of increase.
Exponential population growth rate (r)
A constant proportion by which a population of a species with continuous reproduction changes in size at each instant in time. AKA Intrinsic rate of increase.
Survivorship curve
A graph based on survivorship data (lx) that plots the number of individuals from a hypothetical cohort (typically of 1000 individuals) that will survive to reach different ages.
Cohort life table
A life table in which the fate of a group of individuals during the same time period (a cohort) is followed from birth to death.
Static life table
A life table that records the survival and reproduction of individuals of different ages during a single time period.
Population regulation
A pattern of population growth in which one/more density-dependent factors: Increase population size when numbers are low, decrease population size when numbers are high.
Stable age distribution
A population structure that does not change from one year to the next.
Life table
A summary of how survival and reproductive rates in a population vary with the age of individuals. In species for which age is not informative/difficult to measure, life tables may be based on the size/life history stage of individuals.
Type III survivorship curve
A survivorship curve in which individuals die at very high rates when they are young, but those that reach adulthood survive well later in life.
Type II survivorship curve
A survivorship curve in which individuals experience a constant chance of surviving from one age to the next throughout their lives.
Type I survivorship curve
A survivorship curve in which newborns, juveniles, and young adults all have high survival rates and death rates do not being to increase greatly until old age.
K-selected organisms
At carrying capacity, selection is going to favor efficiency (the one who can work the most and use the least amount of resources). Exists around equilibrium. No big seed set- they have one or two offspring and have good parental care. More resistant. Usually the most favored of selections. ex., Whales, Elephants
Mx=
Birth rate
K=
Carrying capacity
dN=
Change in population
Geometric growth
Change in the size of a population by a species with discrete reproduction by a constant proportion from one discrete time period to the next.
Exponential growth
Change in the size of a population of a species with continuous reproduction by a constant proportion at each instant in time.
Logistic growth
Change in the size of a population that is rapid at first, then decreases as the population approaches the carrying capacity of its environment.
dt=
Change in time
Communities with large physical disturbances
Favors r-selection (huge burst during opportunity). ex., Alaska in the spring
r=
Intrinsic rate of natural increase
R0=
Net reproductive rate
Density-dependent
Of/referring to a factor that causes birth rates to change as the density of the population changes. Birthrate/deathrate changes. Oscillates throughout carrying capacity (K).
Density-independent
Of/referring to a factor whose effects on birth and death rates are independent of population density. Birthrate/deathrate stays the same.
r-selected organisms
Opportunists Take the opportunity to explosively grow (rapid rate of growth). Low density organisms until opportunity arises. Big seed set- they have lots of offspring with almost no parental influence. More resilient ex., grass.
K/2=
Optimal yield Maximum amount of sustainability without a net gain/loss (it all evens out).
rN=
Population growth
N=
Population size
Regulated communities
Regulated by different populations and seasonalities. Complex food/energy loops. Population size regulation. No sign of huge populations of one organism (meaning a lot more competition). Favors K-selection. Not very common. ex., the Amazon
lx=
Survivorship
Fecundity
The average number of offspring produced by a female while she is of age x (denoted Fx in a life table).
Carrying capacity (K)
The maximum population size that can be supported indefinitely by the environment. Constantly changes depending in different factors (ex., seasons).
Net reproductive rate (R0)
The mean number of offspring produced by an individual in a population during its lifetime.
Doubling time (Td)
The number of years it takes a population to double in size.
Survival rate
The proportion of individuals of age x that survive to be age x+1. (denoted Sx in a life table).
Survivorship
The proportion of individuals that survive from birth (age 0) to age x (denoted lx in a life table).
Age structure
The proportions of a population in each age class.
Ecological footprint
The total area of productive ecosystems required to support a population.
t=
Time
