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18 Cards in this Set
- Front
- Back
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Key Concepts
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Data from population ecology studies help biologists evaluate prospects for endangered species and design effective management strategies.
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life table
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summarizes the probability that an individual will survive and reproduce in any given year over its entire lifetime.
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Survivorship
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is a key component of a life table and is defined as the proportion of offspring produced that survive, on average, to a particular age.
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survivorship curve
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is a plot of the logarithm of the number of survivors versus age.
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Three general types of survivorship curves
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Type 1, 2, 3
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Type 1 curve
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survivorship throughout life is high, and most individuals approach the maximum life span of the species; humans show this type of survivorship curve.
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Type 2 curve
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most individuals experience relatively constant survivorship over their lifetimes; songbirds have this curve.
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Type 3 curve
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result from high death rates early in life, with high survivorship after maturity; many plants have type III curves.
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A population's growth rate is the change in the number of individuals in the population (N) per unit time (t).
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If no immigration or emigration is occurring:
growth rate = N r |
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intrinsic rate of increase, rmax
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When birth rates per individual are as high as possible and death rates per individual are as low as possible, r reaches a maximum value
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Exponential Growth
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occurs when r does not change over time. It does not depend on the number of individuals in the population.
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density independent
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When increases in the size of a population do not affect r
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Logistic Growth
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-Carrying capacity
-population density |
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Liebig’s Law of the Minimum
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the environmental factor in smallest supply will limit the growth of the population
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How Do Metapopulations Change through Time?
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-metapopulations―a population of populations.
-the overall number of individuals stays relatively stable |
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Why Do Some Populations Cycle?
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-population cycles—regular fluctuations in size.
-depend on some density-dependent factor. Predation, disease, or food (example) |
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How Does Age Structure Affect Population Growth?
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age—has a dramatic influence on the population’s growth over time.
-The age structure of a population tends to be uniform in developed countries and bottom-heavy in developing countries. |
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Analyzing Change in the Growth Rate of Human Populations
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has increased over the past 250 years
-As of 2008, there are over 6.6 billion people -overpopulation is linked to declines in living standards, political instability, and acute shortages of basic resources. -The future of the human population hinges, in part, on how many children each woman living today has, in part on the survival rates and in part on future fertility |
