Characteriatics of population

• Population


  Consists of all organisms that live in a particular area
• Demography


  The statistical study of population and their change over time
• Measures of population

  • Population size (total number of individuals)
  • Population density (number of individuals per unit area or volume)
• Population size


  • Larger populations may be more stable than smaller populations because they're likely to have greater genetic variability and thus more potential to adapt to changes in the environment through natural selection
• Population density


  • A member of a low-density population-where organisms are sparsely spread out – might have more trouble finding a mate to reproduce with than individuals in a high-density population
• Adaptation


  Population size can affect potential for adaptation because it affects the amount of genetic variation present in the population
• Density


  Can have effects on interactions within a population such as competition for food and the ability of individuals to find a mate
• Quadrats method


  1. Hammer nails from soil

  2. Tie and make a quadrant

  3. Select plant species

  4. Observe species present

  5. Calculate percentage frequency
• Percentage Frequency


  Number of sampling units in which the species occurs/Total number of sampling units employed for the study x 100
• Frequency value


  Indicates the number of times that a plant species is present within the number of sample quadrant
• Transect line


  1. Stretch a measuring tape between two quadrats at regular intervals

  2. Can show the effect of abiotic factors on organism distribution
• Mark-recapture method


  1. Capture a sample of animals and mark them

  2. Recapture the animals to determine population size
• Species dispersion patterns


  • Uniform dispersion
  • Random dispersion
  • Clumped dispersion
• Uniform dispersion


  Individuals of a populations are spaced more or less evenly, e.g. plants that secrete toxins to inhibit growth of nearby individuals
• Random dispersion


  Individuals are distributed randomly, without a predictable pattern, e.g. dandelions and other plants that have wind-dispersed seeds
• Clumped dispersion


  Individuals are clustered in groups, e.g. plants that drop their seeds straight to the ground or animals that live in groups
• Clumped dispersion causes


  Uneven resource distribution or cooperative social behaviors
• Population distribution


  The geographic area where a particular population of a species occurs, determined by the local availability of appropriate habitat
• Habitat generalists


  Their populations spread out continuously across the landscape
• Habitat specialists


  Only occur in specific places where a certain type of ecosystem occurs
• Geographic range


  The total geographic area occupied by a species
• Life history traits


  • Fecundity (reproduction rate)
  • Semelparity (single reproductive event)
  • Iteroparity (multiple reproductive events)
• Natural selection


  Influences life history traits based on factors like energy availability, predation, and disease, leading species to make trade-offs between growth, reproduction, and survival
• Life table


  Summarizes birth and death rates for organisms at different stages of their life
• Survivorship curve


  A graph that shows what fraction of a population survives from one age to the next
• Age-sex pyramid


  A snapshot of a population in time showing how its members are distributed among age and sex categories
• POPULATION


  Group of individuals of a single species inhabiting an area with the potential to interbreed
• Populations


  • Dynamic entities
  • Population ecology focuses on the various factors that affects a population
  • Population studies are significant in solving practical problems such as controlling pest, management of populations
• Population size


  Total number of members a species has
• Migration


  Large-scale movement of a species to another area
• Population Density


  Number of species present in a given space
• Population dispersion


  Distribution of the species in a specific space at a given time
• Natality


  Species birth rate
• Mortality


  Rate of death within a species
• Sex Ratio


  Ratio of male to female in the population
• Age structure


  Proportionate numbers of people in different age categories in a given population for a defined time
• Migrations


  • May be a seasonal or permanent movement of a species towards new locations in search of food, better environment conditions, or reproductive opportunities
  • Can change established ecosystems, thus making it an important factor in population ecology
• Random dispersion


  Species have no definitive pattern and may be found in the area sporadically
• Uniform dispersion


  Species is dispersed evenly within an area with similar distance between each species
• Clumped dispersion


  Species tends to live and move about in groups