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Noushi 9
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GCSE Biology Note on Biology iGCSE Notes, created by Noushi 9 on 28/03/2016.

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Noushi 9
Created by Noushi 9 over 9 years ago
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Section 4

a) The organism in the environment

Population - All the organisms of the same species living in an ecosystem at a particular time

Community - All the populations of different organisms interaction with their habitat

Habitat - A place where specific organisms live

Ecosystem - A community of organisms interacting with each other and their habitat/environment

  • Quadrats. Populations size - Count no. of species in square. Repeat and avg. Multiply avg. by area of field.
  • Quadrats. Distribution of organisms - Place quadrants in different locations. Compare the density/no. of species

b) Feeding Relationships
  • Only 10% of energy transferred because:
  • Some parts of the organism are not eaten (roots)
  • Some of the food is indigestible (Bones,cellulose)
  • Some of the food absorbed forms excretory products (urea)
  • Most of the food is used for respiration, movement, active transport. Little is left for growth or protein
c) Cycles
  • H2O - evapouration, transpiration, condensation, precipitation
  • C - respiration, photosynthesis, decomposition, combustion
d) Human influences on the environment
  • SO2 = Sulphuric acid. Acid rain (SO2 & NOx) = Acidification of water and sea ∴ kills aquatic life and trees, erodes limestone buildings
  • CO = Binds to haemoglobin. Asphyxiation
  • Greenhouse gases = Water vapour, CO2, nitrous oxides (NOx), Methane (CH4), CFCs (refrigerator coolants)
  • Global warming= Polar ice caps melt, Sea level rise, Changes in rainfall (drought/floods), Extinction of polar species
  • Deforestation = leaching, soil erosion, disturbance of water cycle (less transpiration, more drought/flooding), disturbances of the balance of O2 and CO2 in atmosphere (less trees & trees burnt)
  • Leached nitrates from fertilisers = algal blooms develop, sun blocked, plants die, ↓O2, fish die, (NO3 supply stops so algal blooms die), lots of decomposition by fungi/bacteria, Biological Oxygen Demand (BOD) ↑, everything dies. EUTROPHICATION
  • Sewage - Contains lots of bacteria/micro-organisms + nutrients, bacteria decompose sewage, bacteria respire, BOD ↑, fish die (∴ nutrients ↑,algal blooms, eutrophication)
  • Detergents,fertilisers and sewage can cause eutrophication