bio unit 2 (post mocks)

• 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 

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 

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 

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 

• 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 

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

INDEX OF 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