population - group of single species living in a certain place

• size, density, dispersion, demographics
• population range - area throughout which a population occurs
  • no population occurs in all habitats around the world
  • changes as the environment changes
• dispersion - how organisms are spaced
  • randomly spaced - when organisms don’t interact much
  • uniformly spaced - due to competition for resources
  • clumped spacing - most common form, due to strong social interaction or important resource in a certain area
  • human effect - humans altering the environment changes dispersion
• metapopulations - networks of distinct populations that exchange individuals
  • occurs where suitable habitats separated by unsuitable habitats
  • source-sink metapopulations - organisms sent from better areas (source) to bolster worse areas (sink)
• population growth - will exceed resources if unchecked
  • sex ratio - number of births directly related to number of females
  • generation time - average interval between birth of individual and its offspring
  • cohort - group of individuals of the same age
  • survivorship - percentage of original population that survives to given age
• biotic potential - rate population will grow if no limits exist
• sigmoidal growth curve - shows limits of population growth due to carrying capacity
• density-dependent factors - based on the number of organisms
  • population increases >> mortality increases or birth rates decline (negative feedback)
  • Allee effect - where growth rate actually increases as population increases
  • resources, disease, increased aggression, hormonal changes
• density-independent factors - natural disasters

r strategy - rapid population growth

• suited for populations far below carrying capacity
• small, short-lived growth phase
• reproduces rapidly w/ large litters

K strategy - low rate of growth

• suited for populations near carrying capacity
• takes longer to get to carrying capacity (K)
• longer generations, smaller litters
• extended parental care