Seneca

• Successful breeding

  • Individuals with the best chances of survival are the most likely to breed successfully (because they survive)
• Natural selection is not random
• The individuals that have the greatest chance of surviving will be those who can adapt to their environment, so natural selection favours these individuals.
• Successful breeding

  • Individuals with the best chances of survival are the most likely to breed successfully (because they survive)
• Best characteristics survive

  • The characteristics responsible for the greater chance of survival are more likely to be passed on to the next generation.
• Modelling Natural Selection


  1. Randomly scatter an equal number of white grains of rice, and grains dyed green onto a large piece of white card

  2. Give someone else 10 seconds to pick up as many pieces of rice as they can using tweezers

  3. Repeat this several times
• On average more white grains will remain on the card than green pieces
• White grains


  Camouflaged prey that survive to reproduce
• Green grains


  More likely to be eaten by the 'predator' (the tweezers)
• This model does not represent natural selection perfectly because the 'prey' is not moving and it the human players may be biased in selecting grains
• Camouflage

  Camouflage is an adaptation that helps prey blend into their surroundings. Prey with better camouflage are more likely to be able to hide from predators to survive and reproduce.
• Extinctions

  Extinction happens when there are no individuals of a species left in the world. A change in abiotic (physical) or biotic (relating to organisms) factors can cause an extinction if a species cannot adapt fast enough.
• Antibiotic Resistance

  • Within a population of bacteria, some will have random mutations (random change in DNA).
  • The mutated bacteria are resistant to antibiotics and so they are able to survive, whilst the non-resistant bacteria die.
  • The resistant bacteria can reproduce rapidly because their competition (non-resistant bacteria) has been destroyed by the antibiotic.
  • When the resistant bacteria reproduce, they produce genetically-identical copies. These copies will all be resistant to the antibiotics.