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18 Cards in this Set
- Front
- Back
Population/Population Ecoloy
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A group of individuals of a single species living in the same general area
the study of populations in relation to the environment |
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Density
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The number of individuals per unit area or volume.
Determined by 4 factors: Birth rate, death rate, emigration, immigration. |
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Dispersion
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The Pattern or spacing among individuals or subgroups within a population.
Influenced by scale, as well as environmental and social factors. |
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Types of Dispersion
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Clumped: individuals aggregate in patches. Influenced by resource availability and behavior.
Uniform: Individuals are evenly spaced. Influenced by social interaction, such as territoriality. Random: each individual is independent of others. |
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Demography
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Study of vital statistics of a population and how they change over time.
Focus on death/birth rates. |
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Life table
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Age-specific summary of survival pattern of a population.
Best constructed by following cohort. |
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Survivorship curves
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Type 1: Humans. High life expectancy with a gradual taper off in later years.
Type 2: Squirels. Linear decline from birth to death. Type 3: Clams. Poor life expectancy for young, slowly levels out for older individuals. |
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Semelparity
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"Big-Bang" reproduction. Species that focus all energy into a single reproduction period before death. Annual plants. Salmon (digest internal organs to focus more energy to repro).
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Iteroparity
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Species that reproduce offspring repeatedly over time. Perrenial plants. Humans, most mammals.
Must balance reproduction and survival |
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Population growth terms
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r: growth rate. If r=0, no growth. if r > 0, population growing.
K: carrying capacity of an ecosystem. Exponential growth: uninhibited growth up to K. Logistic growth model: per-capita rate declines as carrying capacity is reached. dN/dT = rMAX * N * (K-N)/K |
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k-selection/r-selection
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K-selection: Selects for life history traits that are sensitive to population density. Slow growth rate. Stays close to capacity.
r-selection: Selects for life history traits that maximize reproduction. (Semeparous) |
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Population Change/Classes of Mortality
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Density-independent: Birth rate and death rate do not change with population density. ie: weather
Density-dependent: birth rates fall and death rates rise with population density. Negative feedback. Negative feedback stabilizies population change. Positive feedback is rare, and typically destabilizes a population. |
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Territoriality
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Territoriality can limit population growth. When the population density becomes high, all the good territories are occupied.
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Health/Predation
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Higher density population leads to more rapid spread of pathogens.
As prey population increases, acute predation may be present. Rates of predation and predator population are higher as density increases. |
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Intrinsic factors of population size
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Intrinsic (physiological) factors can regulate some population sizes.
A rise in the stress hormone Cortisol has been detected in some populations with increased population interactivity. Cortisol can reduce reproductive output. |
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Population stability/fluctuation
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Extreme fluctuations in population size are typically more common in invertebrates than in large mammals.
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Metapopulations
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Groups of populations linked by IMMIGRATION and EMIGRATION.
Large populations distinct from each other, but linked. ie: groups of islands. |
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Ecological footprint concept
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Summarizes the aggregate land and water area needed to sustain the people of a nation.
One measure of how close we are to the carrying capacity of earth. |