ecol population characteristics

• Sea Otter


  Enhydra lutris
• Sea Otter


  • Use stones to pry shellfish and break them open on their bellies while swimming on their backs
  • Kelp Beds, Shallow Waters, Pacific Coast
• Population ecology


  The branch of ecology that studies the structure and dynamics of populations
• Population


  A group of similar individuals of the same species living in the same place at the same time, members interact with each other, mate, rear their young, compete for food, space, and other resources
• Major characteristics of a population


  • Population size
  • Population density
  • Population dispersion
  • Age structure
• Population size


  Number of individuals in a population at a given time
• Population size


  • 102,691,858 Filipinos as of October 11, 2016
  • 109,035,343 persons in the Philippines as of 01 May 2020
• Population density


  Number of individuals of a population in a certain space at a given time
• Population density


  • 343 Filipinos/km^2 of Philippine land
  • 14 angel fish/cu m^3 of sea water
• Population dispersion


  The spatial pattern in which members of a population are found in their habitat
• Types of population dispersion

  • Random distribution
  • Uniform distribution
  • Clumped distribution
• Random distribution


  The position of individuals of a population are independent of the other, uniform resources and environmental conditions, members of population do not repel/attract each other
• Random distribution


  • Plants whose seeds are wind-dispersed, oyster larvae
• Uniform distribution


  Individuals of a population are more or less evenly distributed, when members of population compete for resources that are scarce and spread fairly evenly, members of population are antagonistic to each other and defend their access to resources
• Uniform distribution


  • Desert plants (creosote bush), penguins
• Clumped distribution


  Patches or groups of organisms scattered over a given area, most common, resources are patchy, "social" behavior of some animals, protection from predators
• Clumped distribution


  • Herds of grazing animals, schools of fish, flocks of birds, plants on steep mountainsides, heavy-seeded plants
• Immigration


  The influx of new individuals into a population
• Emigration


  The dispersal of individuals from a population
• Temporal distribution


  • Circadian
  • Influenced by tidal fluctuations
  • Lunar
  • Seasonal
  • Due to successional changes
  • Due to evolutionary changes
• Age structure


  The relative proportion of individuals in each age group of a population
• Age structure categories


  • Preproductive (younger than age of sexual maturity)
  • Reproductive (age of sexual maturity)
  • Postproductive (older than age of sexual maturity)
• If proportion of each age class stays the same


  Birth = deaths, stable age distribution, stable populations with relatively the same numbers in each of the age classes
• If higher proportion of pre-productive and reproductive age classes


  High potential for population growth
• Birth rate


  The number of young produced per unit of population per unit of time, major agent of population growth
• Death rate


  The number of deaths per unit of time, major agent of population loss
• Births > deaths


  Population increases
• Births < deaths


  Population decreases
• Births = deaths


  Zero population growth
• Biotic potential of a population

  The capacity of a population for growth (increase in size), varies among populations
• Intrinsic rate of increase (r)


  The rate at which a population could grow if it had unlimited resources, the number of new individuals per existing individual per unit time
• Exponential growth


  When a population does not have resource limitations and the population can grow at its intrinsic rate of increase (r), starts slow then proceeds faster as the population increases
• Characteristics of populations with exponential growth

  • Reproduce early in life, little parental care
  • Have short generation times
  • Can reproduce many times (long reproductive life)
  • Produce many offspring each time they reproduce
  • High dispersal rates, able to colonize harsh environments
  • Opportunistic species
• Populations with exponential growth


  • Weeds
  • Insects
  • Many small egg-laying animals
• No population can grow indefinitely
• Environmental resistance


  All the factors acting together to limit the growth of a population
• Carrying capacity (K)


  The number of individuals of a given species that can be sustained indefinitely in a given space, biotic potential and environmental resistance determine the carrying capacity
• Logistic growth


  Involves exponential growth at first when population is small and a steady decrease in population with time as the population approaches carrying capacity
• Factors affecting carrying capacity

  • Competition
  • Immigration and emigration
  • Natural and human-caused catastrophic events
  • Seasonal fluctuations in food supply, water, hiding places, nesting sites
• Characteristics of populations with logistic growth


  • Produce fewer young, provide them with parental care
  • Long-lived, low dispersal rates, poor colonizers of disturbed habitats
  • Tend to respond to changes in population density through changes in birth and death rates rather than through dispersal