Term
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Definition
| the number of individuals of a population per unit area or volume |
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Term
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Definition
| the pattern of spacing among individuals within the boundaries of the population |
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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 |
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Term
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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 |
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Term
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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 |
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Term
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Definition
| age specific summaries of the survival pattern of a population. created by monitoring a cohort of individuals of the same age. |
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Term
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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. |
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Term
| type I survivorship curve |
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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. |
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Term
| type II survivorship curve |
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Definition
| intermediate, a constant death rate over the organism's life span. |
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Term
| type III survivorship curve |
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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 |
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Term
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Definition
producing thousands of eggs in a single reproductive opportunity before it dies.
ex- salmon |
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Term
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Definition
repeated reproduction. produce relatively few but large offspring each time they reproduce, and they provision the offspring better.
ex- wolves |
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Term
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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 |
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Term
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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. |
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Term
| explain how ecologist may estimate the density of a species |
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Definition
| mark and recapture, sample plots |
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Term
| explain how limited resources and trade-offs may affect life histories |
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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 |
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Term
| compare the exponential and logistic models of population growth |
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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. |
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Term
| explain how density-dependent and density-independent factors may affect population growth |
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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. |
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Term
| explain how biotic and abiotic factors may work together to control a population's growth |
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Definition
| biotic factors such as food resources and competition limit growth. abiotic factors such as availability of nutrients also limit growth |
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Term
| describe the problems associated with estimating Earth's carrying capacity for the human species |
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Definition
| due to technology, there's no way to know which limiting factor will ultimately be responsible for our capacity. |
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Term
| define the demographic transition |
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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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