biology task 1 year 11 mod 3 + 4

• Ecosystem

  The combination of all organisms (biotic factors) living in a community and all non-living features (abiotic factors) with which they interact
• The distribution of the different Australian ecosystems is due to the variation in biotic and abiotic factors found within each particular area
• Terrestrial ecosystems

  • Desert
  • Woodland
  • Temperate forest
  • Grassland
• Abiotic factors in terrestrial ecosystems

  • Rainfall
  • Temperature
  • Soil texture
• Aquatic (marine or saltwater) ecosystems

  • Mangroves
  • Swamps
  • Wetlands
• Abiotic factors in aquatic ecosystems

  • Salt concentrations
  • Light availability
  • Pressure
  • Water salinity
• Abiotic factors


  Unevenly distributed throughout an ecosystem and include: temperature, pressure, light availability, wind, pH etc.
• Abiotic factors can have an impact on the distribution and abundance of organisms in an ecosystem
• In aquatic ecosystems, organisms are mainly impacted by salinity, light availability, gas concentrations and water temperature
• In terrestrial environments, organisms are mainly impacted by temperature and rainfall (water availability)
• Simplest community interactions


  • Predation
  • Competition (including allelopathy)
  • Symbiosis (mutualism, commensalism and paratism)
• Abiotic factors create selection pressures that select for different types of organisms and hence affect biotic factors
• An organism's ecosystem provides it with nutrients, water, shelter and opportunities to mate
• Other living things compete with it for these resources
• Selection pressures


  Changes in the environment resulting in some resources becoming limited and individuals have to compete for these resources
• Selection pressures drive natural selection
• If a variation has a genetic basis (e.g. mutations) these variations are passed down from the surviving parents to the offspring
• Selection pressures


  • Abiotic factors (temperature, light intensity, soil type, water availability, gas concentration in water)
  • Biotic factors (competition between members of a species for the same limited resources, predators, availability of prey)
• Distribution


  Where the species is found
• Abundance


  How many individuals of that species live throughout the ecosystem
• Abiotic and biotic selection pressures affect the distribution and abundance of organisms in an ecosystem by causing fluctuations or changes in population numbers and movement
• Ecology


  The study of interrelationships between different types of organisms and their environment
• Ecologists collect information to understand and record changes in plant and animal populations over time
• Ecologists assess biodiversity so that management plans can be put into place before development and land clearing goes ahead in a range of environments
• Ecologists usually wish to determine the size of a population (total number of organisms present) and the density of organisms (the total number of organisms per unit area)
• Quadrats


  Sampling technique used by ecologists to estimate plant species abundance
• Percentage cover method


  Quadrats cover randomly selected representative areas for estimating the percentage of cover of an area
• Mark-release-recapture technique


  Sampling technique used by ecologists to estimate animal abundance
• Abundance = number captured x number recaptured / number marked in recapture
• Sampling techniques e.g. beating tray, sweep net, tullgren funnel, pitfall trap, kick sampling, longworth small mammal trap, counting from a plane, radio transmitters attached to animal body
• Capturing animals requires various trapping techniques, all designed so that animals are unharmed (e.g. traps, nets, small pits)
• Some techniques such as radio-tracking and the use of electronic detection devices avoid the need for recapturing the animals
• UAVs (unmanned aerial vehicles or drone are now becoming a more common way to monitor wildlife populations
• Transects


  Commonly used to measure the distribution of a species in an ecosystem
• Natural selection is the main reason as to why there are changes in population over time
• Cane toads have very unique characteristics such as feeding mainly at night, being ground dwellers, absorbing water through their skin, can also produce toxins that allow them to feed on reptiles and having no known predators</b>
• Cane toads evolve in a process known as spatial evolution - they have the fastest hopping style than all toads in Australia. This allows them to expand by 10 to 15 km per year in invasion
• In cane toad areas, the red bellied black snake's head became smaller as they were able to see that the larger snakes received a great amount of toxin as they were able to eat the larger cane toads but the smaller headed red bellied black snakes can't eat the large cane toads and die
• There was a huge reduction in population among the introduction of the cane toads for the Northern Quoll as they have not learned and adapted to realise that the cane toads are poisonous
• Prickly pears were introduced to Australia to make a cochineal dye for coats but became a huge pest as the parent branch easily detached and grew (population increased)