population
a group of individuals of a single species that occupy the same general area
population density
the number of individuals of a species per unit area or volume (ecologists use sampling techniques to estimate)
dispersion pattern
the way the individuals are spaced within their area
clumped dispersion pattern
when individuals are grouped in patched ex. a school of fish (most COMMON in nature, results from unequal distribution of resources in the environment)
uniform dispersion pattern
when individuals are dispersed in an even manner ex. king penguins (results from interactions between the individuals of a population)
random dispersion pattern
when individuals are spaced in an unpredictable way ex. dandelions (varying habitat conditions and social interactions make this dispersion patter RARE)
survivorship curves
plots survivorship as the proportion of individuals from an initial population that are alive at each stage
life tables
track the chance of an individual in a given population surviving to various ages
Clumped, uniform, and random
What are the 3 types of dispersion patters?
A population is a localized group of individuals of species.
What is the relationship between a population and a species?
Clumped inside fallen logs or dead trees
What dispersion pattern would you predict in a forest population of termites, which live in damp rotting wood.
Chances of surviving is initially low but increases after an individual reaches maturity.
How dies the chance of survival change with age in organisms with a Type III survivorship curve?
per capita rate of increase
average contribution of each individual to population growth
exponential growth model
an idealized picture of unregulated population growth; the rate of population increase under ideal conditions, no restrictions on the organism to live, grow, and reproduce
limiting factors
environmental factors that restrict population growth
logistic growth model (S curve eg fur seals)
a description of idealized population growth that is slowed by limiting factors as the population size increases
carrying capacity
the maximum population size that a particular environment can sustain
When N is 1/2 K (population = 1/2 carrying . At this population size there are more reproductive individuals than at lower population sizes and still lots of space or other resources available for growth. (N=population size, K=carrying capacity)
In logistic growth at what population size is the population increasing most rapidly? Explain why.
Density-dependent rates
declining birth rates and rising death rates in response to increasing population density (increased density causes population grown rate to recline by reducing birth rate and/or increasing death rate
Food and nutrient limitations, insufficient territories, increasing in disease and predation, accumulation of toxins
List some of the factors that may reduce birth rate or increase death rate as population density decreases.
Type I curve
Produce few offspring but take good care of each one increasing the likelihood that they will survive to maturity (eg humans - high survivorship)
Type II (2) curve
Produce a medium amount of offspring and cares little for each one with survivorship constant over the life span - no more vulnerable at one stage of life than another (straight line eg squirrels, lizards, rodents)
Type 3 curve
Produce many offspring and takes care of none with low survivorship for the very young followed by high survivorship for those few individuals that live to a certain age (eg oysters, nile perch produce 16 million eggs but most die young)
If there are no influencing factors the population will rise rapidly then even out when a factor appears.
How would a population grow rapidly?
A j-curve; when a population rapidly rises causing the data on a graph to be shaped like a J
What is the shape of exponential growth on a graph?
G = rN
What is the equation for the exponential growth model?
G = rN x (K - N)/K
What is the equation for the logistic growth model?
Boom and bust, predator-prey, and herbivore-producer
What are the 3 types of population cycles?
Maximum sustained yeild
harvesting a resource as a level which can be sustained without population decline
Density-independent
have same effect on population growth regardless of density
life history
the traits that affect an organism's schedule of reproduction and death make up its _______________
Hare population cycles are not primarily caused by food shortage
In one experiment, increasing food supply to hares increased their population density, but the population continued to show cyclic collapses. What might you conclude from these results?
Sustainable resource managment
harvesting a resource without damaging it
To protect wildlife from overharvest yet maintaining lower population levels so that growth is high and mortality from resource limitation is reduced
Explain why managers often try to maintain populations of fish and game species at about half their carrying capacity.
demographic tranistion
a shift from zero population growth in which birth rates and death rates are high but roughly equal to zero population growth characterized by low birth and death rates
age structure
used to predict a populations future growth; it is the number of individuals in different age groups
population momemtum
in a population in which r = 0, the continuation of population growth as girls in the reproductive age group reach their reproductive years [an age structure with a broad base has a high proportion of children and a high birth rate because on average, each woman is substantially exceeding the replacement rate of two children per couple. When this occurs, the proportion of women of childbearing years increases and now a situation called __________________ exists. }
r-selection because r (the per capita rate of increase) is maximized
One life history pattern is typified by small-bodied, short lived animals that develop and reach sexual maturity rapidly, have a large number of offspring, and offer little or no parental care AND/OR plants like dandelions that produce thousands of seeds. Ecologists hypothesize that selection for this set of life history traits occurs in environments where resources are abundant permitting exponential growth. What is this called and why?
K-selection because carrying capacity K is maximized. Population growth limited by density dependent factors.
One life history pattern is typified by large-bodied, long lived animals that develop slowly and produce few but well cared for offspring AND/OR plants like coconut palms that produce few seeds that are well stocked with nutrient rich material (the plant's version of parental care). Ecologists hypothesize that selection for this set of life history traits occurs in environments where population size is near carry capacity. What is this called and why?
the death rate declines before the birth rate, creating a period when births greatly outnumber deaths. this also sets up population momentum
During the demographic transition from high birth and death rates to low birth rates and death rates, countries usually undergo rapid population growth. Explain why.
ecological footprint
an estimate of the amount of land required to provide the raw materials an individual or a nation consumes including food, fuel, water, housing, and waste disposal; it is one approach to understanding resource availability and usage
population ecology
the study of how and why population changes
per capita rate of increase (factor r in G=rn, per capita means per person)
the average contribution of each individual to population growth
S Curve
the curve is known as the logistic growth model curve, idealized population growth that is slowed by limiting factors as the population size increase
boom-bust cycle
dramatic fluctuations in density; rapid exponential growth that is typically followed by population falls to a minimal level (eg lemmings)
intrinsic rate of growth
The rate at which a population increases in size if there are no density-dependent forces regulating the population
Type III for a population experiencing r-selection; Type I for a population experiencing r-selection.
Refer to Module 36.3. Which type of survivorship curve would you expect to find in a population experiencing r-selection? K-selection?
maximum standard yield
harvesting should be done at a level that produces a constant yield without forcing a population into decline.
The 1981 "boomlet" is a consequence of rapid reproduction in 1946-1965, as girls born during the baby boom entered their reproductive years
Point out an example of population momentum in figure 36.10