19. Organisms and their environment

• Transfer of energy:

  • the sun is the principal source of energy input to biological system
  • energy flows through living organism: light from the sun, chemical energy in organism
  • energy is eventually transferred to the environment as heat
• Food chain - showing the transfer of energy from one organism to the next, beginning with a producer

  • energy is transferred by ingestion, each time transferred by 10%

  
• Trophic level - the position of an organism in a food chain, food web, pyramid of numbers/biomass
• Why does having many trophic level is inefficient (<5):

  • the energy loss every trophic level would be too great - apex predators would not gain any energy
  • at each level, heat is lost by respiration

  Why does humans eating plants more efficient:

  • only need little amount for a meal oppose to feeding animals to get meat
  • when raising an animal: plants loses energy in the environment, animals loses energy to the environment = not efficient
• Food web - a network of interconnected food chains that make up an ecosystem
• Producer - an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis
• Consumer - an organism that gets its energy by feeding on other organisms (primary, secondary, tertiary, quaternary)
• Herbivore - an animal that gets its energy by eating plants
• Carnivore - an animal that gets its energy by eating other animals
• Decomposer - an organism that gets its energy from dead/ waste organic material
• Impacts of overharvesting/foreign species on a food chain/web:

  • n. of producer would increase if primary consumer decreases
  • but n. of secondary consumer and others would decrease since there is not enough food
  • KNOCK-ON EFFECT
• Pyramid of number:

  • width of box = n. of organism at that trophic level
  • DOESN'T have to be in pyramid shape - number of organism can increase up the food chain
  • shows how many of those in higher trophic level feed on the n. of those below them

  
• Pyramid of biomass:

  • shows how much mass the creature at each level would have without all the water they have in them (dry mass)
  • ALWAYS pyramid - mass of organism decrease as they go up food chain
  • gives information about trophic level, energy transfer & feeding patterns

  
• Water cycle:

  A) evaporation

  B) transpiration

  C) condensation

  D) precipitation

  E) infiltration

  F) surface run-off

  G) through flow

  H) perculation

  I) groundwater flow

  
• The carbon cycle:

  • carbon is taken from the atmosphere through photosynthesis
  • carbon passed onto animals & decomposer by feeding
  • returned to the atmosphere through respiration, decomposition and combustion

  Effect of combustion and deforestation:

  • releasing more CO2 out into the atmosphere than the CO2 taken in from plants
  • disrupt carbon cycle - CO2 out > CO2 in

  
• The nitrogen cycle:

  • deamination: taking nitrogen from air to convert to ammonia
  • decomposition of plants and animals return nitrogen back to the soil -> converted to ammonia -> then to ammonium ions
  • nitrification: ammoniums produced by decomposition of amino acids are oxidised -> nitrite -> nitrate carried out by nitrifying bacteria
  • nitrogen-fixing bacteria: provide usable nitrogen for plants (nitrate)
  • denitrifying bacteria: convert nitrogen containing substance into atmospheric nitrogen

  
• Nitrogen fixing bacteria provide usable nitrogen for plants through:

  • may exist in root where they live (nitrogen fixation)
  • lightning
  • microorganism
• Population - the number of living organism of a species
• Community - all of the populations of different species in an ecosystem
• Ecosystem - a unit containing the community of organisms and their environment interacting together
• Animals compete for:

  • food
  • water
  • shelter
  • territory
  • mates (for breeding)
• Factors affecting rate of population growth:

  • food supply: quantity and quality
  • predation: is predator population falls = prey population will rise
  • disease: high death rate = low population growth
• Sigmoid curve:

  1. Lag phase - no increase in n. of the population: no adaptation yet
  2. Log phase - exponential increase in n. of population: lots of nutrients -> high n. of reproduction, limiting factor does not limit much
  3. Stationary phase - plateau in population growth (carrying capacity reached): limiting factors slows growth
  4. Decline phase - exponential decrease in population (DR>BR): lack of food, competition, disease

  
• Ecological relationships:

  • predation: between predator and prey - size of one population affect the other (e.g. fox/rabbit)
  • mutualism: provide benefits to each other (e.g. oxpeckers/buffalo)
  • parasitism: only one benefit (parasite) - they live off the host (e.g. ticks/sheep)
• Effect of population growth:

  • greater demand for leisure and recreational space
  • increase demand for housing
  • demand for a variety of foods
  • more car = increase demand for roads