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Transcript of Population Ecology
"big bang"/semelparity (semel, "once" parity, "to beget")
one reproductive opportunity
ex: salmon return to fresh-water stream, produce thousands of eggs in single shot then die
Density, Dispersion, and Demographics
Exponential vs. Logistic Growth Model
Lydia & Celia
Density- numbers of individuals per unit area or volume
Exponential vs. Logistic Growth Model
Exponential Growth: growth begins gradually and then increases rapidly, ideal population without limits or carrying capacity
Logistic Growth: growth increases rapidly then plateaus when it reaches the carrying capacity, within limits
Density-dependent factors: a situation in which population growth is reduced by overcrowding of the environment through predators and competition (the birth/death rate changes with density)
Density-independent factors: situations where other factors such as weather/environmental conditions and disturbances may affect a population's carrying capacity (the birth/death rate is unaffected by density)
Chapter 53 Guided Reading
-Global Human Population
Population Ecology- the study of populations
in relation to their environment.
Dispersion- the pattern of spacing among individuals within the boundaries of the population
Population- a group of individuals of a single species living in the same general area that are influenced by similar environmental factors and breed and interact with one another.
Global Human Population
Uniform: species exhibit uniform spaces between them
Clumped: individuals aggregated in patches
Random: position of individual is independent of other individuals
How do scientists estimate the number of individuals in a population?
=individuals/area of space
Demographics- the study of vital statistics of a population and their change overtime
3 characteristics that define a population?
What causes patterns in dispersion?
dispersion of resources
varying environmental conditions
increased protection from predators
territoriality makes organisms with antagonistic social behaviors decrease likelihood of individuals inhabiting nearby space
cohort- group of individuals of the same age, followed from birth until death to gather data for life table/survivorship curve
life tables- age-specific summaries of survival pattern of a population
survivorship curve- a plot of the proportion or numbers in a cohort still alive at each age
Life Table/Survivorship Curve based on data from a cohort:
idealized, species specific survivorship curves
3 types of species:
Type I organisms- low probability of dying early (iteroparous)
Type II organisms- constant probability of dying throughout life
( between iteroparous or semelparous)
Type III- high probability of early death (semelparous)
Abiotic vs. Biotic
Density dependent factors are biotic factors:
2) Competition for Resources
Density independent factors are abiotic factors:
2) Habitat Destruction
K-selection vs. r-selection
K-selection: density dependent selection (selection for life history traits that are sensitive to population density)
Long gestation periods (several months), slow maturation, extended parental care, and longer life spans.
r-selection: density independent selection (selection for life history traits that maximize reproductive success in environments with low density)
Short gestation periods, mature quickly, little to no parental care, and possess short life spans.
Global population variation due to:
Overall trend: exponential, but beginning to slow down
Demographic transition- associated with increase in health car and sanitation and
improved education (especially for women)--> high birth rate, low death rate
Age structure- relative number of individuals of age in population
• Rapid growth (lots of young)
• Slow growth (lots of young and middle age, slightly less old)
• No growth (lots of middle-ages, less young)
Major Limiting Factor for Human Population Growth:
• Ecological footprint- land and water required by person (city or nation) to produce all resources it consumes and absorb all waste generated
Infant mortality- number of infant deaths per 1,000 live births
Life expectancy at birth- predicted average length of life a birth