Unit 8.2

• Ecology


  The study of the interactions of organisms with other organisms and the physical environment
• Levels of ecological organization

  • Habitat
  • Population
  • Community
  • Ecosystem
  • Biosphere
• Demography


  The statistical study of a population
• Demographic factors


  • Population density
  • Population distribution
  • Growth rate

  
• Population density


  Number of individuals per unit area
• Population distribution


  Pattern of dispersal of individuals across an area of interest
• Population distribution patterns


  • Uniform
  • Clumped
  • Random
• Limiting factors


  Environmental aspects that particularly determine where an organism lives
• Limiting factors


  • Light
  • Water
  • Space
  • Mates
  • Food
• Rate of natural increase (r)


  Depends on the number of individuals born each year, and the number of individuals who die each year
• Biotic potential


  The maximum rate of natural increase for a population that can occur when resources are unlimited
• Factors influencing biotic potential


  • Usual number of offspring surviving to reproductive age
  • Amount of competition within the population
  • Age of and number of reproductive opportunities
  • Presence of disease and predators
• Cohort


  Composed of all the members of a population born at the same time
• Survivorship


  The probability that newborn individuals of a cohort will survive to a particular age
• Survivorship curves


  • Type I
  • Type II
  • Type III
• Age distribution


  The proportion of the population that falls into various age categories

  
• Age groups


  • Prereproductive
  • Reproductive
  • Postreprodutive
• Semelparity


  Members of a population have only a single reproductive event in their lifetime
• Iteroparity


  Members of the population experience many reproductive events throughout their lifetime
• Exponential growth

  Rate of population growth increases as the total number of females increases
• Phases of exponential growth curve


  • Lag phase
  • Exponential growth phase
• Logistic growth


  Occurs when limiting environmental factors oppose growth
• Phases of logistic growth curve


  • Lag phase
  • Exponential growth phase
  • Deceleration phase
  • Stable equilibrium phase
• Carrying capacity


  The maximum number of individuals of a species the environment can continuously support
• Density-independent factors


  The population density does not influence the intensity of the factor's effect
• Density-dependent factors


  The percentage of the population affected increases as the population density increases
• Density-dependent factors


  • Competition
  • Predation
  • Parasitism
• Life history


  Characteristics of a population such as the number of births per reproduction, the age of reproduction, the life span, and the probability of an individual living the entire life span

  
• 1. selection


  In unstable or predictable environments, population growth is controlled by density-independent factors, and population size is low relative to K
• 1. strategists


  Produce large numbers of offspring, have a small body size, mature early, have a short life span, do not invest energy in parental care, and tend to be good dispersers and colonizers
• 1. selection


  In stable, predictable environments, population size is controlled by density-dependent factors, and population size tends to be near K
• 1. strategists


  Produce small numbers of offspring, have a large body size, mature late, have a long life span, invest energy in parental care, and tend to be strong competitors
• The human population is undergoing exponential growth, with a present size of over 8 billion people
• The doubling time of the human population was previously estimated at 35-60 years, but experts believe it will take longer to reach 12-14 billion as it would put extreme demands on resources
• Human population growth over time


  • 1800: 1 Billion
  • 1930: 2 Billion
  • 1960: 3 Billion
  • 2012: 6 Billion
  • 2022: 8 Billion

  
• More-Developed Countries (MDCs)


  North America, Europe, Japan, and Australia, with slow population growth, high standard of living, and a demographic transition that has stabilized population growth
• Less-Developed Countries (LDCs)


  Latin America, Africa, and Asia, with rapid population growth and low standard of living
• Strategies to reduce population growth in LDCs


  • Family planning programs
  • Social progress to reduce desire for large families
  • Delay the onset of childbearing
• Age groups in population age structure


  • Prereproductive
  • Reproductive
  • Postreproductive

  
• MDCs have a stable age structure, while most LDCs have a youthful profile and are experiencing population growth, and even reducing births to 2 per family in LDCs would result in population growth because of the age profile