populations in ecosystems

• population

  group of organisms of the same species living in the same habitat
• community

  all the populations of different species in the same area
• ecosystem

  all the organisms living in a community as well as the abiotic and biotic conditions of an environment
• niche

  role of species within an organism
• abiotic factors

  non-living conditions: temperature,soil,oxygen and co2 conc

  light intensity, pH
• biotic factors

  living conditions: predation, competition, food availability
• factors affecting population size:

  abiotic factors

  biotic factors

  • interspecific competition
  • intraspecific competition
• abiotic factors impact on population size:

  when abiotic factors are ideal, the population size can increase

  • plants and animals are adapted to abiotic conditions
• interspecific competition:

  organisms of different species compete for same resources with limited supply - territory/food/water
• intraspecific competition

  organisms of same species compete for the same resources

  • compete for mating - courtship
• interaction between predator prey

  population sizes of predator and prey are interlinked
• investigating size of a population:

  mark-release-recapture method

  random sampling - quadrats
• mark-release-recapture

  estimate size of population for mobile organisms - moving

  • capture initial sample and mark them (record) - ethical
  • release initial sample for a period of time
  • second sample is captured 
  •  record the no. that was marked and the total no. of organisms that was captured in 2nd trial
• ethical considerations of mark release recapture method:

  mark should cause no harm

  • non toxic
  • shouldn't increase or decrease chances of predation
• reasons the estimation is not accurate

  we assume that population size is constant

  we assume that animals redistribute evenly when we release them
• random sampling

  quadrats

  • align 2 tape measures into an area
  • using a random coordinate generator 
  • place the quadrat at the given area and collect data - frequency of plants
• succession

  change in the ecological community over time
• primary succession

  pioneer species colonising (can adapt to survive in harsh conditions - abiotic factors) - starts at bare rock and no soil

  • their decomposition changes abiotic factors to become less harsh

  enables other species to survive 

  •  increases the biodiversity (species richness and number of organisms increases) - creating a climax community
• secondary succession

  succession is disrupted

  • plants and animals are destroyed but soil remains
• two features of a climax community

  stable community (over long time)

  populations stable

  abiotic factors (more or less) constant 
• conservation of habitats - managing succession

  destruction of habitats - due to human activities and needs

  managing succession

  • able to conserve habitats