OCR Gateway GCSE - Biology B2

OCR Gateway GCSE - Biology B2

1. Classification and living together

   • Organisms are classified into discrete groups
   • Order of classification: Kingdom, Phylum, Class, Order, Family, Genus, Species
   • Organisms are classified using natural systems
     • This gives us information about evolutionary relationships
   • Similar organisms will compete with each other for food

2. Energy flow and recycling

   • Pyramids of biomass are harder to construct but always form pyramids
   • Pyramids of Biomass and numbers can show feeding relationships
   • Energy is lost from each stage of a food chain
   • Food chains are limited to a small number of trophic levels
   • Recycling of carbon involves: Photosynthesis, Feeding, respiration and decomposition
   • Recycling of nitrogen involves the action of four types of bacteria

3. Adaptation and natural selection

   • Heat loss from organisms depends on their surface area to volume ratio
   • Organisms in hot dry areas have adaptations to: increase heat loss, move on sand, cope with lack of water
   • Darwin's theory was first widely criticised but now is mostly accepted
   • Darwin's theory of natural selection involves variation, competition, survival of the fittest and selective reproduction
   • Examples of natural selection occurring today are: Warfarin resistance in rats, antibiotic resistant bacteria and frequency of colour in peppered moths

4. Population, pollution and sustainability

   • Human population has been increasing exponentially
     • This has led to: CO2 levels rising leading to Global warming, Sulfur dioxide causing acid rain and CFCs breaking down the ozone layer
   • Removing waste, producing food and supplying energy in a sustainable way will help to conserve habitats and organisms
   • Pollution can be measured using direct methods or by using indicator species
   • Conservation is important to: protect our food supply, prevent damage to food chains, protect organisms for medical uses and protect habitats for people to visit