Investigating Selection
- Created by: jessicawarren
- Created on: 18-05-16 17:29
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- Investigating Selection
- Antibiotic resistance
- Directional selection- individuals with alleles for characteristics of extreme type more likely to survive and reproduce
- Could be response to environmental change
- Bacteria involving antibiotic resistance example of DS
- 1) Some individuals in population have allele that gives them resistance to antibiotics
- 2) Population exposed to antibiotic, killing bacteria without resistant allele
- 3) Resistant bacteria survive and reproduce without competition, passing allele for antibiotic resistance to offspring
- 4) After time, most organisms in population will carry antibiotic resistance gene
- Human Birth Weight
- Stabilising selection- individuals with alleles towards middle of range more likely to survive and reproduce
- Occurs when environment isnt changing, reduces range of possible characterisitics
- Example of stabilising selection is human birth weight
- 1) Humans have range of birth weights
- 2) Very small babies less likely to survive- find it hard to maintain body temperature
- 3) Giving birth to large babies difficult, they are less likely to survive too
- 4) Conditions most favourable to medium sized babies- weight of human babies tends to shift towards middle of range
- Interpreting data
- Describe what data shows- quote graph
- Suggest cause
- Aseptic Technique
- Used to prevent contamination of cultures by unwanted organisms
- Contamination can affect growth of microorganism being investigated
- Disease causing microbes may also make you ill
- Regularly disinfect work surfaces to minimise contamination
- Work near bunsen flame. Hot air rises, microbes drawn away from culture
- Sterilise wire inoculation loop before and after each use by passing through hot bunsen flame for 5 seconds
- Briefly flame neck of glass container of broth just after opening and just before closing-prevents unwanted organisms falling in
- Sterilise all glass ware before and after use e.g. in autoclave
- Antibiotic resistance
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