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What two pieces of data are needed to mathematically determine density? |
Number of organisms and area of habitat |
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Density |
Number of individuals per unit area |
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Dispersion |
The pattern of spacing of individuals |
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Formula N=mn/x |
Number of second sampling. |
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Formula N=mn/x |
Number released in first sampling. |
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Formula N=mn/x |
Number of marked individuals in second sampling. |
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Explain the impact of immigration and emigration on population density. |
They alter the density of populations and increase gene flow between populations. |
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Clumped dispersion pattern |
Animals group around food (social animals). |
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Uniform dispersion pattern |
Animals are dispersed evenly with aggressive territoralism. |
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Random dispersion pattern |
Organisms are randomly dispersed, just where they land. |
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Cohort |
A group of individuals of the same age. |
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Population statistic that demographers have a particular interest in? |
Birth and death rates (helps create a life table). |
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Survivorship curve I (one) |
Most individuals live to older age. Small number of offspring. Lots of parental care. |
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Survivorship curve II (two) |
Individuals live and die at consistent rate. Medium number of offspring. |
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Survivorship curve III (three) |
Many individuals die during first stages of life but those that survive live long. Large number of offspring. No parenting. |
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What does a reproductive table show? |
Age specific summary of reproductive rates in a population. (Measured by reproductive rates of a cohort.) |
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On what is the life history of an organism based? |
The traits that affect an organism’s schedule of reproduction and survival from birth to death. |
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What three variables form the life history of a species? |
Age of reproduction How often an organism reproduces How many offspring per reproductive episode |
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Semelparity |
Single reproductive episode before death (release eggs) can wait for right conditions, release a lot survival rate of offspring is low. |
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Iteroparity |
Multiple reproductive cycles over the course of its lifetime more dependable environments. |
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Two critical factors for determining if a species will evolve toward semelparity or iteroparity. |
Survival rate of offspring Likelihood that the adult will survive to reproduce again |
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Explain the effect of offspring care on parental survival in kestrels. |
There appears to be a negative correlation between brood enlargements and parental survival. |
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What is the advantage to using per capita birth and death rates rather than just the raw numbers of births and deaths? |
Per capita gives average of the number of offspring per individual and number of deaths per unit of time. |
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What will the per capita birth and death rates be if a population is demonstrating zero population growth? |
They will be equal. |
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What does it mean for a population to be in exponential population growth? |
A population that is growing without limitation of resources. |
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What are two examples of conditions that might lead to exponential population growth in natural populations? |
Excess of food and water (resources) Free to reproduce as often as possible |
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What is carrying capacity? |
Maximum population size that an environment can sustain. |
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What are six examples of limiting resources that can influence carrying capacity? |
Space Water Food Mate availability Shelter Predator |
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In the logistic population growth model, the per capita rate of increase approaches zero as the _____ _____ is reached. |
Carrying capacity |
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K-selection |
Density-dependent selection, have few offspring, parent heavily |
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R-selection |
Density-independent, lots of babies, no parents |
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Density-independent regulation |
Provides regulation by reducing birth rate and increasing death rates (competition for food) |
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Density-dependent regulation |
Regulation of population regardless of population density (lightning strikes and there is a fire) |
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Explain negative feedback’s role in the regulation of populations. |
It keeps the population at or near carrying capacity through affecting birth and death rates in a large (close to K) population. |
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Negative feedback mechanism: Competition for resources |
Organisms compete for food and water (Mice have a limited insect supply) |
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Negative feedback mechanism: Territoriality |
Organisms compete for space by fiercely defending an area (Mountain lions have large territories) |
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Negative feedback mechanism: Disease |
Diseases increase death rates by killing weak organisms (Bats have fungus) |
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Negative feedback mechanism: Predation |
Predators control prey population and vice versa (Number of foxes and rabbits in field fluctuate together) |
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Negative feedback mechanism: Toxic wastes |
Some organisms (bacteria/yeast) make toxic wastes that kill some population (Yeast makes alcohol which builds up until death) |
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Negative feedback mechanism: Intrinsic factors |
Hormonal/physiological changes in animals based on food (If women are nutrient deficient they stop menstruating) |
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Importance of immigration and emigration in metapopulations. |
A metapopulation is when two or more populations are linked, it is important to have constant immigration and emigration. |
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Human population growth since 1650. |
We have been exponentially growing until lately. We have slowed down. (2.2% in 1962, 1.2% in 2009) |
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Demographic transition |
Movement from high birth and death rates to low (This has happened in both Mexico and Sweden since 1750) |
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Afghanistan |
Large younger population (Prediction: explosive growth rate) |
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United States |
Even number from 0-55 (Prediction: grow slowly) |
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Italy |
Less children than adults (Prediction: no growth) |
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Why do infant mortality and life expectancy vary so greatly between certain countries? |
They reflect a quality of life and parental choices. |
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Can the world’s population an ecological footprint that is currently the average American’s footprint? |
The average American footprint is 10 and it is unsustainable at 1.7 (Over using resources!) |
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