4. ecology

• Outline the correlation between average global temperatures and concentrations of carbon dioxide since the start of the industrial revolution (200 years ago).

  1. The increase in both is not linear.
  2. There have been fluctuations in average global temperature but overall there has been an increase of 0.8 °C.
  3. Carbon dioxide concentrations have risen at an increasingly greater rate.
  4. However, this correlation does not prove carbon dioxide caused global temperature increase
• How is energy lost between trophic levels (5 things)?

  1. some materials not consumed by predator
  2. most energy uptaken by food not assimilated - used for movement and location - is lost as heat
  3. lost via cell respiration
  4. lost in faeces
  5. not the entire prey is eaten
• How is peat formed:

  1. when saprotrophs cannot decompose organic material due to anoxic/acidic conditions
  2. waterlogged
• Scientists may simulate a naturally occurring ecosystem to establish how the sustainability of that ecosystem may be influenced by global warming in the following way:

  • Setting up a mesocosm
  • Regulating abiotic factors (such as light, temperature, water availability)
  • Adding biotic factors (such as producers, consumers and decomposers)
  • Monitoring the effect of changing temperature on the biotic factors
  • Data can be collected about nutrient cycling / total biomass / species diversity / balance of producers, consumers and decomposers (over time) to establish the sustainability of the ecosystem
• Species:

  • A group of organisms that can potentially interbreed to produce fertile, viable offspring

  Population:

  • A group of organisms of the same species, living in the same area at the same time

  Community:

  • A group of populations living together and interacting with each other within a given area

  Habitat:

  • The environment in which a species normally lives, or the location of a living organism

  Ecosystem:

  • A community and its abiotic environment (i.e. habitat)

  Ecology:

  • The study of the relationship between living organisms, or between living organisms and their environment
• Anaerobic conditions where methanogens may be found include:

  • Wetlands (e.g. swamps and marshes)
  • Marine sediments (e.g. in the mud of lake beds)
  • Digestive tract of ruminant animals (e.g. cows, sheep, goats)
• Methanogens produce methane from the by-products of anaerobic digestion, principally acetic acid and carbon dioxide:

  • Acetic acid → Methane and Carbon Dioxide  (CH3COO– + H+  →  CH4 + CO2)
  • Carbon Dioxide and Hydrogen → Methane and Water  (CO2 + 4 H2  →  CH4 + 2 H2O)
• Advantages of mesocosms:

  • (They make it possible to) investigate interactions between species, e.g. competition / impact of changing abiotic factors, while other variables are controlled
  • Variables other than the variable being tested will not influence the results
  • Mesocosms can be designed to mimic a natural environment as closely as possible
• Disadvantage of mesocosms:

  • In natural environments there are other abiotic factors/biotic factors that cannot be controlled OR (closed) mesocosms are unrealistic representations of a natural environment
  • The results gained from studying a closed system/mesocosm cannot be directly applied to a natural environment