Human Population

• Population ecology


  The study of population and their interaction with their environment
• Population ecology


  • Gives an insight into the factors affecting fluctuations of population in the context of environmental supporting capacity
• Population dynamics


  The study of how, when, and why populations change over time
• Population density


  (Births + Immigration) - (Deaths + Emigration)
• Population grows when the birth rate exceeds the death rate and declines when the death rate exceeds the birth rate
• Dispersion


  The pattern of spacing among individuals within a population
• Types of dispersion


  • Clumped pattern
  • Uniform pattern
  • Random pattern
• Clumped pattern


  Suggests patchy distribution of habitat or social behavior
• Uniform pattern


  Indicates evenly spaced individuals
• Random pattern


  Implies unpredictable distribution
• Density-dependent factors


  Have an amplified effect as the population increase and a diminished effect as the population decreases
• Density-independent factors


  Affect population indiscriminately and usually environment related
• Limiting factors


  Resource abundance: Availability of food, water, and space impacts population growth
• Exponential growth


  Illustrated with a J-shaped curve, showing the slow initial increase because the number of reproducing individuals is small, and then gradually losing its steepness due to the exponential increase in reproducing individuals
• Logistic growth


  Illustrated with an S-shaped curve, as the population size increases the environmental resources become limited, increasing the death rate and thus slowing the rate of population growth
• Carrying capacity (K)


  The maximum number of individuals of a species that the environment can sustain indefinitely
• As population approaches carrying capacity, competition for resources intensifies, leading to stabilized growth
• Life-history pattern


  The pattern of survival and reproduction events typical for a member of the species
• 1. selection


  Rapid life-history pattern, a strategy common in species that have a small body size, reproduce early, highly mobile, and have a short life span that do not reach sexual maturity
• 1. selection


  Slow life-history pattern, common in large species like mammals and birds that live in more stable environments, have a long life span that reach sexual maturity, larger body size, reproduce later in life, and produce few offspring
• Organism interaction


  Cooperative interactions between species such as mutualism and commensalism also encourage population growth
• Predation


  Yields a negatively impacts predator and prey populations
• Interspecific and intraspecific competition

  For limited environmental resources also regulates population size
• Territoriality


  Limits population density as territory space becomes the desired resource for competing individuals
• Crowding


  Can lead to stress which impacts the population negatively
• Emigration


  The movement away from an area, reduces the negative effects of crowding and benefits both the ones that left to immigrate into a new settlement and the ones that remained behind are allocated more resources
• Human population


  The study of human populations is called demography
• Over the last four centuries, human population growth has demonstrated remarkable changes
• Population increase was relatively slow until about 1650 wherein approximately 500 people lived
• The first billion threshold was reached within the next 200 years, 2 million by 1930, then 4 million by 1975
• Today, the global population is that 7.5 million mark and is increasing by approximately 80 million each year
• Global population increase was now stabilized at 1.1% annually and is projected to decrease down to 0.5% by 2050
• Neolithic revolution


  The development of agriculture, the domestication of animals, and the specialization of labor
• Industrial revolution


  The harnessing of fossil fuels to power machines, greatly improving human capacity
• Large-scale extraction of raw materials for fossil fuels has led pollution and exploitation
• Medical revolution


  The discovery of the causes of infections and how these were transmitted, resulting in massive changes in treating illnesses and vast improvement in public sanitation and personal hygiene
• Between 1347 and 1349, the Black Death caused by the pathogen Yersinia pestis led to formation of plague, ravaged through the Europe and Asia killing 75 to 200 million people, approximately one-third of the human population
• Green revolution


  The development of new agricultural technologies to increase production and efficiency, as a solution for worldwide starvation
• World grain production has more than doubled since the 1960s. Wheat production rose from 10 million tons in the 1960s about 75 million in 2006
• In 2013, high yield agricultural firm the amount of carbon being cycled in the atmosphere