Section 4: Ecology and the environment

• POPULATION

  All members of single species living in the same area at the same time
• COMMUNITY

  Groups of populations living and interacting with each other in an area
• HABITAT


  Environment in which species normally live in
• ECOSYSTEM

  Community and abiotic environment
• QUADRATS

  Rectangular frames of known dimensions that can be used to establish population densities by counting and identifying organisms within frame
• ESTIMATING POPULATION SIZE OF ORGANISM

  METHOD:

  • Place quadrat randomly within sampling area
  • Count the number of members of the same specieswithin the quadrat
  • Repeat this numerous times within sampling area using the same size quadrat
  • Repeat the process in another area to compare results

  CALCULATION:

  Equation to Calculate the Approximate Population Size of an Organism:
• ABIOTIC FACTORS

  Non-living environmental factors that can affect organism in ecosystem

  • Abiotic Factors can affect a range of Species as each organism is adapted to certain environments

  E.G

  Light IntensitySoil Moisture LevelAvailability of WaterOxygen Levels

  Availability of Minerals and Nutrients

  Temperature

  Soil pH

  Carbon Dioxide Levels
• BIOTIC FACTORS

  Interactions between living organisms

  • Biotic Factors will affect all Species as they have the vulnerability of being food to Predators or being a host to diseases that can affect Population of Species

  E.G

  GrazingCompetition for FoodPredation

  Bacteria

  Fungi

  Diseases

  Competition for Shelter
• TROPHIC LEVELS


  Position an organism occupies within feeding sequence.
• PRODUCERS

  Organisms that produce their own organic Nutrients (e.g Plants produce Glucose via Photosynthesis).
• PRIMARY CONSUMERS

  Herbivores that feed on Plants (Producers).
• SECONDARY CONSUMERS

  Predators that feed on primary consumers.
• TERTIARY CONSUMERS

  Predators that feed on secondary consumers.
• DECOMPOSERS

  Organisms that release digestive enzymes on dead organisms or non-living organic matter for energy.
• FOOD CHAINS

  Shows the feeding relationships between living organisms
• FOOD CHAINS (EXPLAIN)

  EXPLANATION:

  • The Flower is the Producer as it produces their own organic nutrients (Glucose) via Photosynthesis
  • As the Flowers (Producer) will be eaten by Snails, these are the Primary Consumers
  • As the Snails (Primary Consumer) will be eaten by Frogs, these are Secondary Consumers
  • As the Frogs (Secondary Consumer) will be eaten by Foxes, these are Tertiary Consumers at the top of the food chain

  
• Food web shows the interdependence between organisms
• Change in population of one organism will affect the population of another organism
• Examples of food chains in the food web:

  • Leaf litter → Earthworm → Shrew → Owl
  • Oak tree → Squirrel → Fox
  • Oak tree → Caterpillar → Shrew → Owl
• Impact of population changes:

  • If population of Earthworms decrease, population of Wood mouse may decrease as well due to less Earthworms to feed on, leading to starvation and death
  • If population of Shrews increase, population of Owl may increase as well due to more Shrews to feed on, increasing chances of survival
• PYRAMIDS OF NUMBERS

  EXPLANATION:

  • In the diagram, the bars represent the population of the organism at each trophic level - the wider the bar, the larger the population
  • As energy is lost to the surroundings from one trophic level to the next, there are usually fewer organisms with each trophic level due to decreasing chances of survival
  • However, some diagrams may not resemble a pyramid as one large producer can feed many small consumers (e.g one Oaktree can feed many Insects)

  
• PYRAMIDS OF BIOMASS

  EXPLANATION:

  • In the diagram, the bars represent the biomass of a population of organisms (calculated by multiplying individual biomass by population)
  • Pyramids of biomass will commonly be upright in shape, as the amount of food available (biomass) decreases with each trophic level as energy may be lost via respiration, incomplete digestion, or excretion/egestion

  
• PYRAMIDS OF ENERGY TRANSFER

  EXPLANATION:

  • In the diagram, the bar shows the amount of energy available for the next trophic level
  • As energy is lost via respiration, incomplete digestion, or egestion/excretion, only 10% of energy is passed on from one trophic level to the next
  • As a result, this limits the trophic level in a food chain

  
• Energy enters most ecosystems in the form of sunlight and is converted into chemical energy by producers via Photosynthesis
• Only 10% of energy stored in organic molecules is transferred via feeding from one trophic level to the next
• Energy is lost to:

  • Respiration: energy is lost as heat energy via respiration to enable movement of an organism
  • Incomplete consumption: energy may be lost as not all of the food may be consumed by an organism (e.g. Bones or Fibres)
  • Digestion / Excretion: energy may be lost due to incomplete digestion, resulting in energy loss via digestion to produce faeces which is broken down by Decomposers
• Living organisms exhale Carbon Dioxide into the atmosphere as a product of respiration to release energy for movement
• Plants fix and remove Carbon Dioxide from the atmosphere via Photosynthesis to synthesize Carbon compounds for growth
• Dead organisms and faeces from egestion are broken down by Decomposers to remove and return Carbon Dioxide gas to the atmosphere
• Incomplete decomposition over a long period of time may lead to fossilization of an organism to form fossil fuels
• Fossil fuels, when combusted, will return Carbon Dioxide back into the atmosphere
• SULFUR DIOXIDE

  EXPLANATION:

  • Combustion of Fossil fuels produces Sulfur Dioxide
  • As a result, Sulfur Dioxide will dissolve in clouds composed of Water droplets to form Dilute Sulfuric acid (Acid rain)

  CONSEQUENCES:

  • Acid rain leaches Minerals and Nutrients out of the soil, causing death of Plants and Trees
  • Acid rain damages the waxy layer of leaves, reducing ability of Plants and Trees to absorb Mineral ions needed for growth
  • Acid rain acidifies rivers and lakes, resulting in death of aquatic organisms
  • Acid rain corrodes Metals (steel) and Limestone in buildings
• CARBON MONOXIDE

  EXPLANATION:

  • Incomplete combustion of Fossil fuels produces Carbon Monoxide, which binds irreversibly to Haemoglobin to reduce capacity of Red blood cells to transport Oxygen

  CONSEQUENCES:

  • Carbon Monoxide may cause constant tiredness due to poor Oxygen transport
  • Carbon Monoxide may cause Emphysema due to insufficient Oxygen via aerobic respiration
  • If Pregnant, Carbon Monoxide may result in insufficient Oxygen for respiration, hindering growth of Fetus