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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
calculating population change

Death rate

Growth rate

Emigration rate

Birth rate

Immigration rate

Calculating Population Change

CRUDE BIRTH/DEATH RATE 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
check for understanding
Check for understanding
  • 4 - I can explain to my peers why populations cant grow in size forever.
  • 3 - I understand what limits populations from growing in size unstopped.
  • 2 - I understand carrying capacity, but need more practice.
  • 1 - huh? Exponential growth? Carrying capacity?
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 size1
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
check for understanding1
Check for understanding
  • 4 - I can explain to my peers different ways that populations increase in size and factors that limit uncontrollable population growth.
  • 3 - I understand different ways that populations grow and limitations to their growth.
  • 2 - I understand how exponential growth, boom and bust, and carrying capacity, but I need more practice.
  • 1 - I am lost population growth.
some populations fit two curves
Some populations fit two curves
  • Herring Gulls
  • Type III (young) & Type II
check for understanding2
Check for understanding
  • 4 - I can explain to my peers how reproductive strategies vary from survivorship types.
  • 3 - I understand how reproductive strategies vary from survivorship types .
  • 2 - I understand, I think, but need to review my notes on reproductive strategies and survivorship types.
  • 1 - Aren’t all organisms the same????
human population
Human Population
  • Demography
    • Science of population structure and growth
  • Human Population is J-shaped curve
  • Thomas Malthus
    • food for people??  famine & disease!!!
      • better crop yields
projecting future populations
Projecting Future Populations
  • Population is increasing; why is death rate going down?
  • Growth rate (r) has started to decline
  • Zero-population growth: birth rate and death rate are equal (S –shaped curve)
  • Projections for 2050 – variation due to fertility rate of less developed countries
    • Low = 7.7 billion
    • High = 10.6 billion
    • Most likely = 9.1 billion
slide27

Highly developed countries – Ex: US, Japan, Germany –

    • low birth rates, low infant mortality rates (6% US; 54% world), long life expectancy (77 US, 67 world), high per-capita GNI PPP ($34,000, $7,000)
  • Developing countries:
    • moderately developed countries (Ex: Mexico, Thailand) – high infant mortality/birth rates, but declining
    • less developed countries (Bangladesh, Niger, Ethiopia)
growth rate
Growth rate
  • Doubling time!! – amount of time for an area to double = 70/r (r = growth rate as %)
    • Which type of country has shorter doubling time?
  • Replacement-level fertility – typically 2.1 children
    • Total fertility rate (world) is above replacement level (about 2.5)
    • Impacting factors: infant mortality rate, population momentum by ## of young females, need/lack of need for children to work (rural), education (especially of women!!)
check for understanding3
Check for understanding
  • 4 - I can explain to my peers zero population growth, total fertility rate, replacement level fertility, and doubling time.
  • 3 - I understand zero population growth, total fertility rate, replacement level fertility, and doubling time.
  • 2 - I understand, I think, but need to review my notes on zero population growth, total fertility rate, replacement level fertility, and doubling time
  • 1 - I understand some of the terms, but not all.
demographic stages
Demographic Stages
  • Pre-industrial Stage
    • Birth and death rates high – poor medical care, limited food supply
    • Modest population growth
  • Transitional Stage
    • Lowered death rate – higher education/improved conditions
    • Rapid population growth
  • Industrial Stage
    • Birth rate decline – urbanization decreases economic reason for many kids, women educated/work, retirement safety nets reduce it
    • 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
check for understanding4
Check for understanding
  • 4 - I can explain to my peers all the different demographic stages, why they occur AND how to read age structure graphs. I should just drop out of HS now .
  • 3 - I understand all the different demographic stages, why they occur AND how to read age structure graphs .
  • 2 - I understand demographic transition and age structure graphs, BUT…..
  • 1 - I am lost and need to hear it all again.