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Chapter 8 Population Change
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Overview of Chapter 8 Principles of Population Ecology
Factors that Effect Population Size Reproductive Strategies Metapopulations The Human Population Demographics of Countries Demographics of United States
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Principles of Population Ecology
Study of populations and why their numbers change over time Important for Endangered species Invasive species Population Group of individuals of same species living in the same geographic area at the same time
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Population Density Population density
The number of individuals of a species per unit area or volume at a given time Ex: minnows per Liter of pond water Ovals below have same population, and different densities
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Change in Population Size
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Change in Population Size
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Calculating Population Change
Death rate Growth rate Emigration rate r = (b – d) + (i – e) Birth rate Immigration rate Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 people
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Maximum Population Growth
Intrinsic Rate of Growth (Biotic Potential) Growth rate under ideal conditions J- Shaped Curve (exponential growth)
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Environmental Resistance
Environmental limits (resistance) Prevent indefinite reproduction Unfavorable food, water, shelter, predation, etc. Carrying Capacity (K) Maximum # of individuals an environment can support Causes leveling off of exponential growth S-shaped curve of logistic population growth
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Population Crash Overshooting carrying capacity can lead to population crash Abrupt decline in population density
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Factors That Affect Population Size
Density Dependent Factor Factor whose effect on population changes as population density changes Examples: Predation Disease Competition Sometimes cause Boom-or-Bust Population Cycles
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Boom-Or-Bust Population Cycles
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Case Study- Predator Prey Dynamics on Isle Royale
As wolf population increases, moose population decreases (and vice versa)
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Factors That Affect Population Size
Density Independent Factors Factors that affects population size, but is not influenced by changes in population density Examples: Killing frost Severe blizzard Fire
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Reproductive Strategies
r-selected species k-selected species -Small body size - Early maturity - Short life span - Large broods - Little or no parental care Probability of long term survival is low Mosquitoes and Dandelions Small broods Long life span Slow development Large body size Late reproduction Low reproductive rate Redwood trees and human beings
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Survivorship
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Some populations fit two curves
Herring Gulls Type III & Type II
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Metapopulations A set of local populations among which individuals are distributed in distinct habitat patches across a landscape Source habitats Sink habitats
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Metapopulations
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Human Population Demography
Science of population structure and growth Human Population since 1980 is J-shaped curve
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Population Increase in Mexico
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Projecting Future Populations
Population is increasing Growth rate (r) has started to decline Projections for 2050 Low = 7.7 billion High = 10.6 billion Most likely = 9.1 billion
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Demographics of Countries
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Demographic Stages Pre-industrial Stage Transitional Stage
Birth and death rates high, modest population growth Transitional Stage Lowered death rate, rapid population growth Industrial Stage Birth rate decline, population growth slow Post Industrial Stage Low birth and death rates, population growth very slow
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Demographic Stages
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Fertility Changes in Select Countries
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Age Structure Diagrams
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Worldwide 29% of human population is under age 15
Could cause large increase in birth rates
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Education of Immigrants into US
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