ms topic 10

• investigation to show how organism distribution is affected by an abiotic factor

  • quadrats - select sample sites with environmental differences, then use quadrats placed at random to measure presence/absence of lichems
  • transect - one site with an environmental gradient, then place quadrats along a transect
  • measure abiotic factor and use either a t test or a correlation test (PMCC)
  • control/measure other variables to prevent them from affecting outcome
• a t test is suitable for comparing the means of two independent samples from a population as it tests for the difference between the means of two sets of values
• how to modify a quadrat method to obtain more accurate results

  • use more quadrats
  • therefore larger area sampled
  • place the quadrats at random / use random number generators for placement
  • to therefore achieve a consistent measure of the mean
• gross primary productivity is the rate at which producers make organic material/biomass/carbon fixation by photosynthesis and it is measured in mass of biomass per area per time
• what happens to energy in the plants which is not eaten by grazing energy

  • the energy either passes onto other animals such as insects or it remains in the plants biomass
  • some of the energy is released in respiration, or through other metabolic processes
• why is the efficiency of energy transfer different between different trophic levels

  • different organisms use/lose different proportions of energy
  • not used because not all digested, not all consumed, some lost by excretion
  • lost because of respiration for movement or maintaining body temperature
• why is energy transfer from sunlight to producers not 100% efficient

  • light reflected from leaf
  • light not absorbed by chloroplast
  • only certain wavelengths absorbed
• NPP (net primary productivity) is GPP - RL - the energy in organisms which transfers onto the next trophic level
• at high light intensities, as temperature increases NPP increases because light is not limiting photosynthesis, so the rate of photosynthesis is greater than the rate of respiration

  at low light intensities, as temperature increases NPP decreases as the photosynthesis rate is limited by light, so respiration increases more than photosynthesis
• how succession changes soil over time

  • pioneer species arrive and colonise bare rock
  • their decay increases the soil depth
  • this allows larger plants to grow due to the increased soil depth
  • this continues until a climax community has emerged
• in the diversity index equation

  • N is the total number of organisms
  • n is the number of organisms per species
• the index of biodiversity is a better measure of biodiversity than counting the number of species only, as it acocunts for the population of the species, as the number of organisms in each species vary
• impact on the introduction of an invasive species

  • native species are now extint in habitat
  • decreasing biodiversity
  • native species' populations decline at differrent rates
  • the loss of some species allowed other to increase
  • the invasive species may have consumed some species before others
• how colonisation of bare rock by lichens results in succession

  • lichens are pioneer species
  • they break down surface of rocks to create soil
  • therefore other plants are able to grow
  • death and decay help to create humus
  • therefore providing niches for either plants or animals
• an ecosystem is a community of organisms and their physical environment.
• advantges of in-situ conservation compared to ex-situ

  • other species are also conserved in the ecosystem, maintaining the food web
  • their behaviour stays natural
  • less inbreeding occurs as gene pool is maintained
• limitations of CITES

  • not all countries sign the treaty as it's voluntary
  • many species move across national boundaries by migration
  • monitoring is too expensive + some poaching may continue
• role of CITES

  • prevents trade of endangered species
  • by countries that ign the treaty
• even though the population of an endangered species may have recovered, they may have health problems

  • as they faced a genetic bottleneck, there's reduced genetic diversity
  • therefore the change of inheriting two harmful recessive alleles increases