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chap 53
population ecology
21
Biology
Undergraduate 2
08/14/2014

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Term
Density
Definition
the number of individuals of a population per unit area or volume
Term
dispersion
Definition
the pattern of spacing among individuals within the boundaries of the population
Term
clumped dispersion
Definition
individuals are aggregated in patches where environmental factors favor growth. may also be associated with mating behavior, and increase the effectiveness of predation or defense.
ex- star fish, wolf pack
Term
uniform dispersion
Definition
evenly spaced dispersion. may result from direct interactions between individuals in the population. often a result of antagonistic social interactions such as territoriality. rarer than clumped dispersion
ex- penguins
Term
random dispersion
Definition
unpredictable spacing between individuals. the position of each individual in a population is independent of other individuals. occurs in the absence of strong attractions or repulsions among individuals or where key physical or chemical factors are constant across the environment. not very common, most populations are at least a little clumped
ex- many plants, dandelions
Term
life table
Definition
age specific summaries of the survival pattern of a population. created by monitoring a cohort of individuals of the same age.
Term
reproductive table
Definition
an age specific summary of the reproductive rates in a population. it is constructed by measuring the reproductive output of a cohort from birth to death.
Term
type I survivorship curve
Definition
flat at the start, reflecting low death rates during early and middle life, and then drops steeply as death rates increase among older age groups. common in large mammals.
Term
type II survivorship curve
Definition
intermediate, a constant death rate over the organism's life span.
Term
type III survivorship curve
Definition
drops sharply at the start, reflecting very high death rates for the young, but flattens out as death rates decline for those few individuals that survive the early period of die-off. usually associated with organisms that produce very large numbers of offspring but provide little or no care
Term
semelparity
Definition
producing thousands of eggs in a single reproductive opportunity before it dies.
ex- salmon
Term
iteroparity
Definition
repeated reproduction. produce relatively few but large offspring each time they reproduce, and they provision the offspring better.
ex- wolves
Term
r-selected populations
Definition
density-independent selection. selection for traits that maximize reproductive success in uncrowded environments. is said to maximize r, the per capita rate of increase, and occurs in environments in which population densities are well below carrying capacity or individuals face very little competition
Term
k-selected populations
Definition
selection for traits that are sensitive to population density ad are favored at high densities. occurs in populations at a density near the limit imposed by their resources, where competition among individuals is stronger.
Term
explain how ecologist may estimate the density of a species
Definition
mark and recapture, sample plots
Term
explain how limited resources and trade-offs may affect life histories
Definition
limited resources mean that organisms must compete for what is available. if the environment is close to it's capacity of individuals, then the competition is going to increase. if parents care extensively for their offspring, then they trade off opportunities to take care of themselves. reproducing is taxing on the parent, so in a highly competitive environment they may not reproduce
Term
compare the exponential and logistic models of population growth
Definition
exponential models model population increase under ideal conditions. the population increases at a constant rate, forming a J shaped curve. In the logistical population model, the per capita rate of increase approaches zero as the carrying capacity is reached.
Term
explain how density-dependent and density-independent factors may affect population growth
Definition
density dependent factors are forms of feedback regulation and cause death rates to increase and birth rates to decrease as density increases. density independent birth and death rates occur because of physical factors.
Term
explain how biotic and abiotic factors may work together to control a population's growth
Definition
biotic factors such as food resources and competition limit growth. abiotic factors such as availability of nutrients also limit growth
Term
describe the problems associated with estimating Earth's carrying capacity for the human species
Definition
due to technology, there's no way to know which limiting factor will ultimately be responsible for our capacity.
Term
define the demographic transition
Definition
the demographic transition is the movement of high birth and death rates, which tends to accompany industrialization and improved living conditions. also associated with an increase in the quality of health care and sanitation as well as improved access to education, especially for women.
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