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Chapter 8 Population Change - PowerPoint PPT Presentation


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Chapter 8 Population Change. Overview of Chapter 8. Principles of Population Ecology Reproductive Strategies The Human Population Demographics of Countries Demographics of United States. Principles of Population Ecology. Population Ecology

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overview of chapter 8
Overview of Chapter 8
  • Principles of Population Ecology
  • Reproductive Strategies
  • The Human Population
  • Demographics of Countries
  • Demographics of United States
principles of population ecology
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
population density
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
calculating population change

Death rate

Growth rate

Emigration rate

Birth rate

Immigration rate

Calculating Population Change

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

r = (b – d) + (i – e)

maximum population growth
Maximum Population Growth
  • Intrinsic Rate of Growth (Biotic Potential)
    • Growth rate under ideal conditions
    • J- Shaped Curve (exponential growth)
environmental resistance
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
population crash
Population Crash
  • Overshooting carrying capacity can lead to population crash
    • Abrupt decline in population density
factors that affect population size
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
case study predator prey dynamics on isle royale
Case Study- Predator Prey Dynamics on Isle Royale
  • As wolf population increases, moose population decreases (and vice versa)
factors that affect population size15
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
some populations fit two curves
Some populations fit two curves
  • Herring Gulls
  • Type III & Type II
human population
Human Population
  • Demography
    • Science of population structure and growth
  • Human Population since 1980 is J-shaped curve
projecting future populations
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
demographic stages
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
age structure
Age Structure
  • The number and proportion of people at each age in a population
world wide
World-wide
  • 29% of human population is under age 15
  • Could cause large increase in birth rates