Key Concepts of Population

• Definition of Terms

  • Population: Groups of organisms of the same species living in the same area at the same time

  • Population Ecology: the study of how populations change over time and space and interact with their environment

• Key Characteristics

  • Population Size: the number of individuals in the population

  • Population Density: how many individuals are in a particular area

  • Population Growth: how the size of the population is changing over time

• Significance of Studying Population Growth

  • Helps scientists make better predictions about future changes in population sizes and growth rates (biodiversity, sustainable growth, and development)

  • Helps scientists understand what causes changes in population sizes and growth rates

  • Gives scientists insight into how organisms interact with each other and with their environment

• Case Studies

  • The American Bison

    • Without human intervention, the plains’ environment of the United States initially supported a Bison population ranging from 15 to 100 million individuals

    • Throughout the 19th-20th century, advances in hunting technologies and practices sharply decreased the population of American Bison to a few thousand, with their 1902 population being merely 21 individuals.

    • With government and private landowner intervention, herds of Bison were protected, enabling some degree of population restoration from 21 to 250 individuals in 1915

    • Due to a variety of environmental factors (disease, predation, weather, human intervention), the current population of Bison reached its environmental carrying capacity of 2500-5000 individuals

  • The Philippine Eagle

    • IUCN Status: Critically Endangered

    • Dr. Dioscoro Rabor (1965) alerted the world of the bird’s endangered status

    • The Monkey-Eating Eagle Conservation Program (1969) was established

Dynamics of Human Population

• Types of Population Rates

  • Birth Rate

    • The number of births occurring in a period of time

    • Formula: (Number of Births / Total Population) * 1000

  • Death/Mortality Rate

    • The number of deaths occurring in a period of time

    • Formula: (Number of Deaths / Total Population) * 1000

  • Population Growth Rate

    • The change in population in a period of time

    • Formula: (Birth Rate - Death Rate) / 1000

• Types of Population Growth

  • Exponential Growth

    • A type of growth that adds increasingly more individuals as the population size increase

    • It assumes constant growth rate, requires an abundance of resources and high environmental carrying capacity

    • Regularly appears in nature, particularly with the introduction of a novel species in an environment

    • May result in dramatic environmental degradation and expensive pest control measures

  • Logistic Growth

    • The population size grows exponentially for a while, but then it slows down and levels off when as it approaches the carrying capacity

    • Able to factor in shifts and fluctuations in a population

    • Based on Pierre-Francois Verhulst’s Logistic Equation

      • The mathematical expression for a particular sigmoid (S-shaped) growth curve in which the percentage rate of increase decreases in linear fashion as the population size increases

• Factors Influencing Population Growth

  • Age Structure

    • The composition of a population in terms of the proportions of individuals of different ages

    • Factors: Education, Birth Control Programs, Quality of Medical Services

  • Lifespan: the length of time for which a person or animal lives or a thing functions

  • Fecundity: the physiological maximum potential reproductive output of an individual (usually female) over its lifetime

  • Carrying Capacity

    • The maximum amount of population that an environment can hold

    • The asymptote, or plateau, of the logistic and other sigmoid equations for population growth

  • Technological Advancements (Medicine, Agriculture, and other Sciences)

• Factors Influencing Population Density

  • Density-dependent Factors: Dependent on the number of individuals living in an area

  • Density-independent Factors: Independent and regardless of the number of individuals living in an area

Ecological Footprint and Climate Justice

• Definition and Key Terms

  • Ecological Footprint: The measurement of the amount of resources a person consumes in his/her day-to-day living, including the energy required to dispose of our waste

  • Carbon Footprint: The amount of carbon dioxide [CO₂/GHG] emissions associated with all the activities of a person or other entity

  • Global Warming: The long-term heating of Earth’s client system observed since the pre-industrial period (between 1860 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gases levels in Earth’s atmosphere

  • Sustainability/Sustainable Development: A type of development that meets the needs of the present without compromising the ability of future generations to meet their own needs

• Significance of Measuring Ecological Footprint

  • Finite resources require us to be more efficient, sustainable with our practices

  • The problem of overconsumption:

    • One American consumes 34x the electricity at home that an Indian consumes

    • Nearly 9/10 Americans commute using a car or van, compared to 1/10 of Indians

• The Climate Justice Movement

  • A social movement acknowledging climate change can have differing social, economic, public health, and other adverse impacts on underprivileged populations, while pushing for climate justice solutions

  • It begins with recognizing key groups are differently affected by climate change and can exacerbate inequitable social conditions