populations/ecosystems

• Habitat-place where an organism lives
• Population- all the organisms of one species in a habitat
• Community-polulations of different species in a habitat make up a community
• Ecosystem- a community, plus all the abiotic conditions in the area in which it lives
• Niche- the role of a species within its habitat
• Adaptation- a feature that members of a sepxies have that increases their chances of survival and reproduction
• Carrying capacity- the maximum stable population size of a species that an ecosystem can support
• Abiotic factors examples:

  • Amount of light
  • Water availability
  • Space available
  • Temp
  • Chemical composition of surroundings
• Intraspecific competition

  1. Population of a species increases when resources are plentiful. As population increases, competition between organisms (of the same species) will increase [for space and food]
  2. Eventually resources such as food and space become limiting.....population begins to decline
  3. Smaller population....less competition for space/food.....population begins to grow again
• Predator- prey relationship

  1. As prey population increases....more food for predators.....predator population increases
  2. As predator population increases.... more prey eaten...prey population begins to fall
  3. Less food for predators (more competition)......their population decreases
• To estimate the number of bluebells in a small woodland:

  1. Use a grid/quadrat/ split area into squares (determining position using random number generator)
  2. Count no./frequency of plants in quadrat
  3. Large sample and calculate mean
  4. multiply mean no. per quadrat by no. of quadrats to calculate total no.
• To investigate distribution of plant from one side of sand dune to other:

  1. Transect/ lay tape measure (from one side to other)
  2. Place quadrats at regular intervals along line
  3. Count plants/ percentage cover/ abundance in quadrats
• • Variation exists within original colonisers/ mutations took place
  • Individuals better adapted to environment/ selection pressures.... greater reproductive success
  • ....more likely to pass on advantageous allele to next generations
  • resulting in a change in allele frequency
• Succession:

  • Colonisation by pioneer species
  • Pioneer species change environment/conditions....(die/ are decomposed helping to form a thin layer of soil... which thickens as more organic material is formed)
  • Environment becomes less hostile.... more suitable for other/new species
  • Change/ increase in biodiversity
  • To climax community
• Features of a climax community:

  • Same species present/ stable community (over long time)
  • Abiotic factors roughly constant over time
  • Populations stable (around carrying capacity)
• intraspecific- within a species
• interspecific- between different species
• Sympatric speciation: (occurs in the same habitat/environment)

  • Random mutations may occur in a population resulting in members becoming reproductively isolated
  • no interbreeding/ gene pools kept separate/ no gene flow
  • differential reproductive success (select) individuals survive/reproduce
  • change in allele frequency over time
  • eventually individuals can no longer interbreed to produce fertile offspring
• Allopatric speciation:

  • geographical isolation... no interbreeding/ gene pools kept separate
  • Variation occurs as a result of mutation(random)
  • Different environments have slightly different conditions.... different selection pressures
  • Different alleles will be more advantageous(selection for different alleles)
  • differential reproductive success (selected individuals survive/ reproduce)
  • changes in allele frequency over time... eventually individuals can no longer interbreed to produce fertile offspring