Ch 53 Population Ecology Flashcards
Density
The number of individuals per unit area or volume
Dispersion
The pattern of spacing among individuals within the boundaries of the population
What two factors influence the spacing of individuals in a population?
1) Environmental factors
2) Social factors
In most cases, it is 1)___ and 2)___ to count all the 3)___ in a population
1) Impractical
2) Impossible
3) Individuals
Sampling
Techniques used to estimate densities and total population sizes
Mark-recapture method (definition)
A method for estimating population size by extrapolating from small samples
Mark-recapture method (steps)
1) Capture, tag, and release a random sample of individuals in a population
2) Marked individuals are given time to remix into the population
3) Scientists capture a second sample of individuals and note how many of them are marked
4) Population size (N) is estimated
Mark-recapture method (Equation)
N = (sn)/x
s = tagged individuals n = second captured sample x = tagged individuals in second sample
The actual density of a population is the result of what?
An interplay between processes that add individuals to a population and those that remove individuals
Process that add individuals to a population
1) Births
2) Immigration
Process that removes individuals from a population
1) Death
2) Emigration
Demography
The study of the vital statistics of a population and how they change over time
Life table
An age-specific summary of the survival pattern of a population
How is a life table best made?
By following the fate of a cohort
Cohort
A group of individuals of the same age
Survivorship curve
A graphic way of representing the data in a life table
Survivorship curve: Type I
Few deaths early on in life, most deaths within a small range of time later in life
Survivorship curve: Type II
Relatively steady number of deaths throughout life
Survivorship curve: Type III
Most deaths occur early on in life
For species with sexual reproduction, demographers often concentrate only on ___ in a population
Females
Fertility table (fertility schedule)
An age-specific summary of the reproductive rates in a population
If immigration and emigration are ignored, a population’s growth rate equals 1)___ ___ minus 2)___ ___
1) Birth rate
2) Death rate
A change in population size equals:
Birth + Immigrants - Deaths - Emigrants
Mathematical expression for population growth
Births - Deaths
Zero population growth (ZPG)
Occurs when the birth rate equals the death rate
Exponential population growth
Population increase under idealized conditions
Logistic population growth
A model where the per capita rate of increase declines as carrying capacity is reached
Carrying capacity
The maximum population size
Logistic population growth models are useful for:
Estimating possible growth
Life history (definition)
Comprises the traits that affect its schedule of reproduction and survival
Life history (traits)
1) The age at which reproduction begins
2) How often the organism reproduces
3) How many offspring are produced during each reproductive cycle
Semelparity (Big-bang reproduction)
Reproduce once and die
Iteroparity (Repeated production)
Produce offspring repeatedly
What kind of environments favor semelparity?
High variable or unpredictable environments
What kind of environments favor iteroparity?
Dependable environments
R-selection
Selects for life history traits that maximize reproduction
Density-independent selection
K-selection
Selects for life history traits that are sensitive to population density
Density-dependent selection
Two general questions about regulation of population growth:
1) What environmental factors stop a population from growing indefinitely?
2) Why do some populations show radical fluctuations in size over time, while others remain stable?
Density-dependent birth and death rates are an example of what?
Negative feedback that regulates population growth
Factors that affect density-dependent birth and death rates:
1) Competition for resources
2) Territoriality
3) Disease
4) Predation
5) Predation
6) Toxic wastes
7) Intrinsic physiological factors
Long-term population studies have challenged what?
The hypothesis that populations are relatively stable over time
