CB4 Natural Selection And Genetic Modification

• The skulls get bigger, showing that the species had bigger brains, they were getting more intelligent and therefore that’s how they were evolving.
• Ardi was 4.4 million years ago.
• Lucy was 3.2 million years ago
• Leakey discovered fossils from 1.6 million years ago. He discovered Homo erectus.
• The evidence that scientists used to show some fossils are older is how deep they are buried in the rock.
• The tools can be dated  by working out the age of the rock they are made from. As the tools become more recent, they get more sophisticated.
• Charles Darwin’s suggested the theory of EVOLUTION by natural selection.
• 1. Individuals vary due to having different genes 2. Organisms compete for resources 3. The best adapted are more likely to survive. This is called NATURAL SELECTION. 4.  These survivors breed and pass on these ‘better adapted ‘ variations to their offspring.

  5. This is repeated over many generations.
• A species may become extinct due to several reasons:

  • Lack of resources like food
  • Predator
  • Disease
  • Change in environment
• Antibiotics kill bacteria. Some bacteria are more RESISTANT to the antibiotics than others and take longer to be killed.
• If you misuse an antibiotic and stop taking it too early this leaves the antibiotic resistant bacteria still alive. They can then spread and cause infections that cannot be treated with antibiotics.
• animals =

  • Multicellular
  • Cells have nuclei but no cell walls
• plants =

  • Multicellular, cells have nuclei and cellulose cell walls. Cells have chloroplasts for  photosynthesis
• fungi = Multicellular. Cells have nuclei and cell walls but contain chitin (not cellulose). Feed on dead matter
• prokaryotes =

  • Unicellular but no nucleus. Have a cell wall that is NOT made out of cellulose.
• protists = Unicellular with a nucleus
• Archaea – single celled organisms, no nucleus and genes contain unused DNA sections
• Bacteria (prokaryotes) – single celled organisms,  no nucleus but there are NO UNUSED DNA sections
• Eukarya – multicellular organisms, have a nucleus and genes contain unused sections
•   The first part of the name gives the genus and the second part the species.
• selective breeding =

  • Select organisms with desired characteristics to breed
  • Select offspring with desired characteristics to breed 
  • Repeat over many generations
• Selective breeding :

  • Used for hundreds of years to improve the quality of animals and crops.
  • Males and females are selected with the characteristics you want and bred together to get the offspring you want
• organisms are generally bred for =

  1. Disease resistance

  2. Yield

  3. Fast growth

  4. Flavour

  5. Coping well with environmental conditions
• concerns of selective breeding =

  1. Animal welfare           

  2.  A lack of variety means that all can be affected by change in conditions
•  A GMO is one which has been produced by changing the DNA of one organism by inserting genes from another.
• Advantages of GM

  1. We can produce insulin to treat Type 1 diabetes by genetically modifying bacteria
  2. We made rice contain the nutrient beta- carotene to stop vitamin A deficiency
  3. We have made crops are resistant to insects
  4.  GM pigs are being developed with human-like organs for transplant.
  5. Faster than selective breeding
• Disadvantages of GM

  1.  GM foods and seeds can be expensive to buy
  2.  Possible contamination of wild types of plants
• genetic engineering of insulin =

  1. Cut out the gene from a human chromosome
  2. Using a restriction enzyme
  3. Cut open the bacterium plasmid using  restriction enzyme.
  4. Insert the gene into the plasmid. The sticky ends are complementary and will match up. The new DNA is called RECOMBINANT DNA.
  5. Use a ligase enzyme to join the sticky ends together.
  6. Insert the plasmid back into the bacteria.