bio unit 2 (post mocks)

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  • Created by: charlie
  • Created on: 16-04-14 17:19

Antibiotics

  • used to treat bacterial diseases - kill / inhibit growth 
  • some prevent bacterial growth by forming bacteria cell wall (leads to OSMOTIC LYSIS)

OSMOTIC LYSIS 

  • antibiotics inhibit enzymes that are needed to make chemical bonds in cell wall 
  • prevents cell from gorwing properly + weakens cell wall 
  • water moves in by OSMOSIS 
  • cell expands + pressure on walls 
  • cell lyses 

RESISTANCE 

  • mutations (changes in base sequence of DNA)
  • change the protein made --> different characteristic expressed 
  • some mutations mean bacteria are no longer affected by antibiotic --> ANTIBIOTIC RESISTANCE 
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gene transmission

VERTICAL 

  • genes passed on during REPRODUCTION 
  • asexual reproduction --> each daughter cell exact copy of parent (exactly same genes)
  • genes for antibiotic resistance found in BACTERIAL CHROMOSOME or PLASMID 

HORIZONTAL 

  • 2 bacteria join together + copy of a plasmid passed from one cell to other --> CONJUGATION
  • plasmids can be passed to member of same species or totally different 

DIAGRAM 

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evolution of antibiotic resistance

natural selection (an ADAPTION is characteristic that increases an organisms chance of survival)

  • individuals show variation in their charactristics 
  • predation, disease + competition creates struggle for survival 
  • individuals with better adaptions, survive, reproduce + pass successful alleles on 
  • number of successful alleles become dominant in pop. 
  • favourable adaptions common in pop. 

IN QUESTIONS - EXPLAIN WHY CERTIN CHARACTERISTICS ARE COMMON (increased)

  • 1) identify why adaptions are useful
  • 2) explain how they have become more common due to natural selection 
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treating antibiotic-resistant infections

MRSA - causes range of illnesses

  • some strains are resistant to nearly all antibiotics 
  • takes a long time to determine which antibiotics will kill the individual strain 
  • PREVENTION MEASURES - patients diagnosed isolated / sterlisiation / hygiene practices 

TUBERCULOSIS - lung disease

  • natural selection led to pop. resistant to range of antibiotics - strains are MULTIDRUG-RESISTANT 
  • TB now involves taking range of different antibiotics for 6 months 
  • becoming resistant quicker than drug companies can make new antibiotics 
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decisions about antibiotic resistance

  • develops by NATURAL SELECTION but shown that things can be done to slow the process 
  • e.g. HYGEINE MEASURES / FINISHING COURSES 

ETHICAL ISSUES 

  • only used in life threatening situations to reduce increase of resistance 
  • but would reduce peoples standard of living 
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species diversity

"number of different species and the abundance of each species within a community"

INDEX OF DIVERSITY :

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human impacts on biodiversity + species diversity

BIODIVERSITY 

"variety of living organisms + ecosystems on earth"

DOFERESTATION 

  • redcuces number of trees + number of tree species 
  • destroys habitats - species die / migrate 
  • can increase species diversity in other areas 

AGRICULTURE 

  • deforestation / hedgerow removal 
  • pesticides - kill organisms (pests)
  • herbicides - reduces plant diversity 
  • competition - crops introduced + outcompete surrounding plants for resources 
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