natural selection and evolution

• Natural selection and evolution

  used to explain how features of the environment apply selective force on the reproduction of individuals in a population

  random mutation resulted in a new finger length allele for the gene

  environmental selection pressure results to be advantageous

  advantageous allele is inherited by members of next gen

  as a result, the new allele increases in frequency in the population
• How natural selection works

  1. mutation creates alternative versions of a gene (allele)
  2. this creates genetic variation between the individuals of a species (intraspecific)
  3. once variety exists, then thee environment can ‘select’

  →when resources are scarce, the environment will select those variations (characteristics) that gives an advantage; selection pressureindividuals with an advantageous characteristics will survive and reproduce
• How natural selection works 2

  1. individuals with an advantageous characteristics will survive and reproduce
  2. therefore they pass on the advantageous characteristics (generations)
  3. next gen, higher proportion of individuals with the successful characteristics

  → over time, the group of organisms become well adapted to its environment (adaptation)
• In Evolution

  whenever a species or a group of organisms is placed under a new selection pressure, different characteristics will be selected

  • most obvious in organisms with a short life cycle
• Pesticides resistance in insects

  pesticides kills pests; insecticides specifically kill insects + applies very story selection pressure

  • if insect has some form of resistance, the resistance characteristic is passed onto next generation
• Microorganisms

  use of antibiotics is a very powerful selection pressure on bacteria

  • once most bacteria have been killed, you tend to feel better + stop taking however this allows the resistant bacteria to survive + reproduce to create a resistant strain of bacteria

  → overuse + incorrect use of antibiotics has led to strains of bacteria that are resistant to the antibiotics; now some doctors prescribe multiple antibiotics reducing chances that bacteria will survive

  • before selection there is variety of levels of resistance - caused by mutations that create genetic variations within species
• Microorganisms 2

  • directly after selection, the least resistant individuals have been killed - all that remains are individuals possessed some level of resistance
  • the population of partly resistant individuals reproduces - the next generation contains a much higher proportion of resistant individuals
  • MRSA bacterium has developed resistance to an ever-increasing range of stronger and stronger drugs

  → medical researchers are struggling to develop new + effective drugs, but the bacterial populations rapidly become resistant to them