Chapter 8 Population Change

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Chapter 8Population Change
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Overview of Chapter 8

• Principles of Population Ecology
• Reproductive Strategies
• The Human Population
• Demographics of Countries
• Demographics of United States

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Principles of Population Ecology

• 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

• Birth (b), Death (d), Immigration (i) and
  Emigration (e) are calculated per 1000 people

r (b d) (i e)
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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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Human Population

• Demography
• Science of population structure and growth
• Human Population since 1980 is J-shaped curve

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Human Population
1 Billion 1800
2 Billion 1930
3 Billion 1960
4 Billion 1975
5 Billion 1987
6 Billion 1999
6.6 Billion 2006
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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
• 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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Age Structure

• The number and proportion of people at each age
  in a population

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Demographics of Specific Countries
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World-wide

• 29 of human population is under age 15
• Could cause large increase in birth rates

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Education of Immigrants into USThe Role of
Education in Society