V. Ecology - Population potential I Posted SV.pdf - V...

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V. Population Potential Learning Outcomes: 1. Identify factors that affect population size. 2. Explain what factors determine carrying capacity. 3. Compare real population growth curves to models. 4. Given specific examples, predict changes in population size due to different abiotic or biotic factors. Readings: Chapter 19 : 402-414; 417-420
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An Overview of Population Ecology A population is a group of individuals of a single species that occupy the same general area at the same time . Individuals in a population rely on the same resources, are influenced by the same environmental factors, and are likely to interact with one another. § Population ecologists study: (1) how individuals in a population are distributed in space and time, and the reasons for those distribution patterns; and (2) the factors that influence a population’s abundance (population size, density), structure, and growth rate.
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Terminology: Population size - number of individuals Density - number of individuals per unit area or volume Age structure - proportion of individuals of different ages Population dynamics - the interactions between biotic and abiotic factors that cause variation in population size. Population growth – an important aspect of population dynamics An Overview of Population Ecology
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Factors affecting population size (N) Changes in population size (N) can be attributed to four factors: 1. Births 2. Immigration - new individuals from elsewhere join population 3. Deaths 4. Emigration - individuals leave population to go elsewhere Increases population size Decreases population size
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Population Growth § These four factors can be incorporated into a mathematical formula for population growth. N t+1 = N t + B – D + I – E § N t+1 = future population size § N t = current population size The population size at some future time period (N t+1 ) equals the current population size (N t ) plus birth and immigrants minus deaths and emigrants.
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What are some other influences? Parental age: - The younger the age of the parents when they reproduce: Faster increase - The older the parents when they reproduce: Slower increase Amount of available resources: More resources Healthier individuals -> live longer -> lower death rate: Increase AND/OR Individuals can spend more time growing, delay reproduction (e.g. long-lived trees): Slower increase Few resources Individuals less healthy -> increases death rate….and they have less energy for birthing healthy offspring: Decrease or slower increase AND/OR If resources are limiting….organisms may put available resources into reproduction and then
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