Topic 8 - Ecology and the Environment

• Habitat


  Place where an organism lives
• Population


  Group of organisms of the same species living in one area together
• Community


  All the different populations that live together in an area
• Ecosystem

  all the organisms living in a particular area and the non-living (abiotic) conditions

  
  

  biotic + abiotic factors interacting in one area at one time
• Interdependence


  term referring to when species depend on each other for food, protection, shelter
• Ecology studies

  distribution of species, abundance of species, interactions between species, interactions between species + abiotic factors
• Quadrats


  study population size of small organisms

  study:

  - number of individual species

  - species richness

  - percentage cover (percentage of quadrats inhabited)

  
  

  PRACTICAL:

  - use random number generator to generate coordinates in area to count species within quadrats

  - repeat, work out mean no. organisms per quadrat

  - CAN COMPARE NUMBER OF ORGANISMS IN 2 DIFFERENT AREAS
• limitations of quadrat

  - can miss individual organisms when counting (human error)

  - identifying species may be difficult (use a species key)
• Abiotic factors


  non-living

  examples:

  LIGHT INTENSITY - photosynthesis

  TEMP - photosynthesis, germination (growth of seeds)

  MOISTURE LEVELS - water for germination / photosynthesis

  SOIL pH

  WIND INTENSITY - pollination, transpiration in plants

  CO2 LEVELS - photosynthesis

  OXYGEN FOR AQUATIC LIFE - respiration
• Biotic factors


  living

  examples:

  NEW PREDATORS - may disrupt ecosystem + food chain

  AVAILABILITY OF FOOD - higher chance of surviving = population increases

  NEW PATHOGENS - no immunity then population decline

  COMPETITION - if one species is better adapted = other species will die
• Trophic levels


  feeding relationships between organisms

  energy flows from the sun --> first trophic lvl (producers convert light energy into chemical energy) --> second trophic lvl (primary consumers) --> third trophic lvl (secondary consumers) --> fourth trophic lvl (tertiary consumers)
• Producers


  produce own organic nutrients using energy from sunlight (plants that photosynthesise)
• Primary consumers

  Herbivores/omnivores (feed on plants)
• Secondary consumers

  Omnivores / carnivores (feed on primary consumers)
• Tertiary consumers

  carnivores/omnivores (feed on secondary consumers)
• Quaternary consumers


  feed on tertiary consumers
• Which way are the arrows in a food chain? (showing energy transfer)

  trophic level 1 --> trophic level 2
• arrows represent what in food chain

  transfer of energy from one trophic level to the next
• Energy passed on

  only the energy that is made into new cells remain with the organism to be passed on.
• how is energy lost between trophic levels?

  - waste products (CO2 + water in respiration)

  - movement

  - generate heat

  - not all of the organism is edible (eg bones to some predators)

  - undigested waste (faeces)
• why are food chains rarely more than 5 organisms long?

  insufficient loss of energy at each trophic level
• Pyramid of numbers

  shows how many organisms at each level of food chain (at each trophic level)
• Pyramid of biomass

  A pyramid that shows the total MASS of all the LIVING organisms in a trophic level.

  
  

  (weight)
• Pyramid of energy

  shows amount of energy (J) contained within the biomass of individual organisms within different trophic lvls
• how much energy is passed on to the next trophic level?

  10%
• Carbon cycle

  The organic circulation of carbon from the atmosphere into organisms and back again

  
  

  1. Carbon taken out of atmosphere by PHOTOSYNTHESIS

  2. Passed on to animals + decomposers by FEEDING

  3. Returned by RESPIRATION of organisms

  4. Additionally returned by COMBUSTION of fossil fuels (created by death + waste of organisms)

  5. returned by CO2 released from decay
• Understand the biological consequences of pollution of air by sulfur dioxide

  Sulfur dioxide:

  - combustion of fossil fuels produces sulfur dioxide if there are sulfur impurities

  - as a result - it will dissolve into clouds composed of water droplets to form sulfuric acid (acid rain).

  - danger = leeches minerals and nutriants out the soil --> death of plants + trees, acidifies bodies of water --> killing aquatic animals, damages waxy layer of leaves --> plants absorption of minerals decreases, corrodes metals on buildings
• Understand the biological consequences of pollution of air by carbon monoxide

  Carbon monoxide:

  - formed when petrol and diesel are burned in combustion engines (incomplete combustion reaction)

  - colourless, odorless and tastless gas

  - danger = binds to haemoglobin instead of oxygen causing you to suffocate + die
• What is the greenhouse effect?

  - When shortwave radiation from the sun strikes the Earth's surface it is absorbed and re-emitted from the surface of the Earth as infrared radiation

  - some emitted heat passes through the atmosphere into space OTHERS are reabsorbed by greenhouse gases --> heat re-emitted in all directions (trapped inside the Earth's atmosphere)
• Greenhouse gases examples

  carbon dioxide

  methane

  water vapour

  nitrous oxides

  CFCs
• Human activity contributes to greenhouse gases

  carbon dioxide - humans massively increases CO2 level by burning fossil fuels in factories, powerstations, houses and vehicles FOR ENERGY

  
  

  nitrous oxide - car fumes contain nitrous oxide (but catylic converters reduce this). Use of fertilisers increases nitrous oxide.

  
  

  methane - lots more cattle on planet to feed population and they all produce methane as a waste product of digestion. Methane also produces by decay in landfills which is increasing

  
  

  CFCs - man made chemicals -> used to be found in aerosols sprays (like deodorant) and fridges. Mostly banned now due to them destroying the ozone layer allowing more UV light in.
• Global warming consequences

  ocean temps increasing (melting of polar ice caps due to increase in temp from greenhouse effect)

  
  

  increasing temps = extreme weather

  
  

  loss of habitats

  
  

  decrease in biodiversity (food chains disrupted)

  
  

  increase in migration + spread of disease + pests
• Biological consequences of water pollution by sewage

  - untreated sewage and nitrates from fertilisers used by farms and pesticides from humans cause great environmental damage

  Process of nitrates and fertalisers:

  - the farmer spreads lots of fertilisers on the field - then it rains and all gets washed off and ends up in the rivers and the lakes (fertiliser has been leeched from farmland to lakes+rivers). This causes a process called eutrophication

  Process for sewage disposal:

  - sewage contains phosphate from detergents and nitrates from urine and faeces, then

  - the sewage gets leaked and released into water systems which causes a process called eutrophication
• Biological consequences of eutrophication

  - the nutrients from the sewage and fertiliser get washed off into ponds + rivers + streams

  - causes rapid growth in algae (phosphate + nitrate)

  - this blocks all the light coming in causing all plants underneath to die-

  when they die --> broken down by bacteria (decomposers)

  - the bacteria use up all the oxygen in the water. It becomes ANOXIC

  - Oxygen levels drop = all other animals die because they can't respire