Biology B2 Revision Mindmap

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  • B2 Revision
    • Classification
      • Artificial system - 1/2 characteristics Natural system - based on evolutionary relationships
      • Kingdom, Phylum, Class, Order, Family, Genus, Species
      • DNA analysis (sequencing the bases in DNA) helps to reclassify organisms - shows similarity
      • Problems: Living things at different stages of evolution, bacteria do not interbreed but reproduce asexually, hybrids are infertile so cannot be classed as species
      • Organisms grouped together usually share recent common ancestor, but may have different features if they live in different habitats
    • Energy flow
      • Pyramids of biomass and numbers show feeding relationships
      • Pyramids of biomass show the dry mass of living material at each stage of a food chain
      • Food chains are limited to a small number of trophic levels
        • Energy is lost from each stage of a food chain - transferred e.g. heat from respiration, egestion, excretion (less useful)
      • Efficiency of energy transfer = energy used for growth/energy input
      • Organisms may belong to more than one trophic level
    • Recycling
      • Carbon cycle: CO2 removed from air by photosynthesis, passed along a food chain and released into the air by respiration, decomposition and combustion (burning fossil fuels)
      • Nitrogen cycle: Decomposers convert protein and urea into ammonia, nitrifying bacteria convert ammonia to nitrates, denitrifying bacteria convert this into nitrogen gas, nitrogen -fixing bacteria fix nitrogen gas (also by action of lighting)
      • Carbon is recycled into nature by marine organisms making shells made of carbonates, shells becoming limestone, carbon returning to the air as CO2 during volcanic eruption or weathering, oceans absorb CO2 - acting as carbon sinks
    • Interdependence
      • An ecological niche describes the habitat that an organism lives in and also its role in the habitat
        • Organisms that share similar niches are more likely to compete, as they require similar resources
        • Remember parasites, mutualism is when both organisms benefit from their relationship - e.g. insects pollenating flowers, pea plants (containing nitrogen-fixing bacteria) - LEARN!
    • Population, pollution and sustainability
      • Human population has been increasing exponentially - more CO2 causing global warming, CFCs, sulfur dioxide causing acid rain - kills fish and trees
        • Whales
  • Organisms that share similar niches are more likely to compete, as they require similar resources


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