Natural Selection

• Children inherit characteristics through heredity descent
• Children are not clones of their parents because of variation
• Darwin suggested that humans selected domestic animals and flock based on selection
• Individual organism do not evolve, instead generations of organisms pass on their traits with variations subjected to selection which over thousands of generations and vast amount of time the population of organisms changes and evolves
• George Cuvier made the statement: “All of these facts... seem to me to prove the​ existence of a world previous to ours, destroyed by​ some kind of catastrophe”.
• Lamarck proposed that if an animal or plant changes during its lifetime to adapt to its environment, those changes will be passed on to its offspring
• The HMS Beagle was a ship which went on a 5 year voyage to discover animals in different parts of the world
• Common descent


  The idea that all living things are related and they have descended from a common ancestor
• Darwin's evolution theory states that similar species must be closely related to each other, or descend from a common ancestor
• Lamarck was wrong because natural selection is not based on need
• First step of natural selection

  The population must show variation in a heritable trait
• Second step of natural selection

  There must be more offspring born than can survive in the environment.
• Third step of natural selection

  There must be selection pressure on the population
• Fourth step of natural selection

  Some organisms must have a survival advantage based on traits they inherited
• Fifth step of natural selection

  Organisms with a survival or reproductive advantage can pass on favourable traits to their offspring
• Selection pressure

  Competition for food, resources, or mates. Predators and environmental conditions also apply
• 1. Population with varied inherited traits
  2. Elimination of individuals with certain traits
  3. Reproduction of survivors
  4. Increasing frequency of traits that enhance survival and reproductive success
• Individuals that are better adapted tend to survive and produce more offspring
• If favourable traits are heritable, offspring are likely to inherit favourable traits
• A species is a group of organisms that can potentially interbreed with eachother to produce viable, fertile offspring
• A group of the same species in a specific area is called a population
• A gene pool is all the genes and alleles that exist in a population
• New species appear when isolated groups experience different environmental selection pressures, thus favouring different traits
• Genetic divergence occurs as groups become more and more different at a genetic level