Natural selection and genetic modification

• Charles Darwins Theory of evolution by natural selection

  Individuals in a population show genetic variation because of differences in their alleles. Predation and competition for resources and disease act as a chance of an organism surviving and reproducing. The organisms born with traits that make them better adapted survive these challenges. This means they reproduce and the alleles from this generation are passed down onto the next generation, and as this process repeats the beneficial characteristics become more common in the species
• Proof of natural selection

  Bacteria can mutate in their DNA like any other organism. These can create new alleles, changing the bacterias phenotype. The best trait for bacteria to have is resistance against particular antibiotics. The bacteria with this trait will live on longer and reproduce many times. This leads to the allele being passed on through offspring and the bacterium survives the antibiotics better.
• Ardi- a fossil

  • 4.4 million years ago
  • Ape-like feet, arms, legs, and a brain size similar to chimpanzees
  • Structure of legs suggest she could walk upright without hand help
• Lucy- a fossil

  • 3.2 million years ago
  • Arched feet more adapted to walking
  • Brain slightly larger than Ardis
  • Structure of leg bones suggests she could walk upright and more efficiently than Ardi
• Leakeys fossils


  Richard Leakey and his team discovered many more recent fossils. One was named Turkana Boy, who was more human-like than Lucy

  • Shorter arms and longer legs
  • Much larger brain size
  • Structure of legs suggest he was even better at walking upright than Lucy.
• The development of stone tools over time

  The Homo species evolved and we can tell this due to the stone tools they would use becoming more complex and therefore their brains were getting larger

  • 2.5 mil years- pebble tools made by hitting rocks together
  • 0.3 mil years- sculpted rocks into shapes like hand axes
  • 300000 years- more complex tools e.g flint tools and wooden spears
  • 200000- present- flint tools and pointed tools including arrowheads appeared around 50,000 years ago.
• How to date stone fossil tools

  1. Looking at the structural features of the fossil
  2. Using stratigraphy- study of rock layers as they get deeper underground they are older
  3. Stone tools are often found with carbon materials so carbon dating can be used to date the materials
• Classification system change over time

  The five kingdom classification is still used, but outdated. Over time, technology has developed further and our understanding of genetics has increased. This led to a rethink by Carl Woese, who proposed a three domain system of classification: Archea (organisms that appear similar to bacteria), Bacteria (true bacteria), and Eukarya ( fungi, plants, animals, protists). This was because there was organisms in the Prokaryote kingdom that weren't closely related at all, leading to a split.
• What is selective breeding?

  Selective breeding is when humans select plants or animals with desirable traits and force them to breed together so that the genes for these traits stay in the population. This can cause:

  • Animals that produce more milk or meat
  • Crops with disease resistance
  • Plants that produce bigger fruit.
• What is genetic engineering?

  Genetic engineering is the modification of an organism's genome to create desired traits or characteristics.
• Genetic engineering process

  1. The desired DNA is cut out with restriction enzymes that recognise specific sequences of DNA and cut the DNA.
  2. The vector (plasmid or virus) is cut open using the same restriction enzyme
  3. Both DNA are left with sticky ends and are mixed together with ligase enzymes (which are able to join up DNA), join together, and form a recombinant DNA
  4. The recombinant DNA is inserted into other cells which use the gene inserted to make the desired protein.
• Benefits and drawbacks of genetic engineering

  • Benefits- useful in agriculture to create herbicide resistant crops and increase crop yields, useful in medicine to produce useful proteins in animals and then extracted from them to help with human illnesses
  • Drawbacks- Many genetically engineered embryos dont survive or have health issues later in life, and transplanted genes in plants may get out into the environment meaning that weeds are also resistant.
• Benefits and drawbacks of selective breeding

  • Benefits: beneficial in agriculture for higher meat yields, beneficial in medical research
  • Drawbacks: reduces the gene pool, interbreeding can cause health problems, if disease appears the population will die alot quicker because of less differing genes