* Natural Selection and Genetic Modification

• Natural selection means 'the survival of the fittest'
• Things like predation, competition for resources and disease act as selection pressures. This means they affect an organism's chance of survival and reproducing.
• Like all organisms, bacteria sometimes develop mutations in their DNA. These can create new alleles which can change their characteristics.
• For the bacterium, the ability to resist this antibiotic is a big advantage. In a host who's being treated to get rid of the infection, a resistant bacterium is better able to survive than a non-resistant bacterium.
• If the bacterium is more likely to survive, it will live for longer and reproduce much more. This leads to the allele for antibiotic resistance being passed on to lots of offspring - natural selection. This is how it spreads and becomes more common in its population of bacteria over time.
• Antibiotic resistance provides evidence for evolution because it makes the bacteria better adapted to an environment where antibiotics are are present.
• A fossil is any trace of an animal or plant that lived a long time ago. They are most commonly found in rocks. Generally, the deeper the rock, the older the fossil.
• By arranging fossils in chronological order, gradual changes in organisms can be observed. This provides evidence for evolution because it shows how species have changed and developed over billions of years.
• Charles Darwin developed The Theory of Evolution. He spent 5 years travelling around the world studying plants and animals on a ship called HMS Beagle.
• Darwin noticed that there was a variation in members of the same species and that those with characteristics most suited to the environment were more likely to survive.
• Alfred Russel Wallace was a scientist who came up with the idea of natural selection. Wallace and Darwin published their papers of evolution together and acknowledged each other's work.
• Wallace's observations provided lots of evidence to help support The Theory of Evolution by natural selection. He realised that warning colours are used by some species to prevent predators from eating them.
• It was Darwin's famous book 'On the Origin of Species' that made other scientists pay attention to the theory. In this book, Darwin gave lots of evidence to support the theory and expanded it.

  This book is also partly why Darwin is better known than Wallace.
• We now understand that all life changes through the process of evolution, and that the evidence suggests we have all descended from a common ancestor.
• What is classification ?

  if all living organisms have descended from a common ancestor, then we are all related in some way.

  we now organise organisms based on how closely related they are.
• What is Antibiotic Resistance ?

  we now understand the importance of finishing the course of drugs to prevent resistant bacteria spreading and we know to constantly develop new antibiotics to fight newly evolved resistant bacteria.
• What is conservation ?

  we now understand the importance of genetic diversity and how it helps populations adapt to changing environments.

  this has led to conservation projects to protect species.
• Human beings and their ancestors are known as hominids. These fossils have characteristics that are between apes and humans.
• Ardi is a fossil of the species Ardipithecus Ramidus. She was found in Ethiopia and is 4.4 million years old.
• What are the features of Ardi's ?

  The structure of her feet suggests she climbed trees.

  She also had long arms and short legs.

  Her brain size was about the same as a chimpanzee's.

  The structure of her legs suggests that she walked upright.

  Her hand bone structure also suggests she didn't use her hands to help her walk.
• Lucy is a fossil of the species Australopithecus Afarensis. She was found in Ethiopia and is 3.2 million years old.

  Lucy also has a mixture of human and ape features, but she is more human-like than Ardi.
• What are the features of Lucy ?

  Had arched feet, more adapted to walking than climbing.

  The size of her arms and legs were between what you would expect to find in apes and humans.

  Her brain was slightly larger than Ardi's but still similar in size to a chimpanzee's brain.

  The structure of Lucy's leg bones and feet suggest she walked upright, but more efficiently than Ardi's.
• Turkana Boy is a fossil of the Homo species. It is 1.6 million years old and has a mixture of human and ape-like features, but is more human-like than Lucy.
• What are the features of Turkana Boy ?

  Short arms and legs that are much more human-like

  His brain size was much larger than Lucy's - similar to a human brain size.

  The structure of his legs and feet suggest that he was even better adapted to walking upright than Lucy.
• A Pentadactyl Limb is a limb with 5 digits.

  You can see pentadactyl limbs in species like: mammals, reptiles and amphibians.

  In each of these species the pentadactyl limb has a similar structure, but usually a different function.

  for example, humans and bats have limbs with 5 digits but we don't use ours to fly.
• The 5 Kingdom Classification System is based on the similarities of organisms and their evolutionary relationships. It is first divided into 5 groups called kingdoms. Including: animals, plants, fungi, prokaryotes and protists.

  The kingdoms are then subdivided into smaller groups that have common features, these groups are: phylum, class, order, family, genus and species.
• What is ARCHEA ?

  Organisms in this domain look similar to bacteria but are actually quite different - they have differences in their DNA and RNA sequences. They were first found in extreme places such as hot springs and salt lakes.
• What is BACTERIA ?

  this domain contains true bacteria.
• What is EUKARYA ?

  this domain includes a broad range of organisms including fungi, plants, animals and protists.
• What is selective breeding ?

  when humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population.
• Organisms are selectively bred to develop features that are useful or attractive. For example:

  • animals that produce more meat or milk
  • crops with disease resistance
  • dogs with a good, gentle temperament
  • plants that produce bigger fruit.
• What is genetic variation ?

  When a species have better characteristics for producing something, so they can produce more in less time. People then breed these species with the better characteristics so that more species will have their characteristics.
• Advantages of Genetic Variation:

  • it is used in medical research
  • used to help with alcohol research
  • helps us understand the behaviour and how people‘s brains work when they are under the influence of alcohol.
• Disadvantages of Genetic Variation:

  • it reduces the number of alleles in a population
  • can cause health problems
  • this can cause serious problems if they catch a disease if they already have a low immune system.
• Tissue culture involves growing cells on an artificial growth medium.

  Whole plants can be grown via tissue culture - it is really easy and really useful too. Plants grown in this way can be made very quickly, in very little space and can be grown all year.
• Plants produced by tissue culture are clones - genetically identical organisms. This means you can use tissue culture to create lines of clones all with the same beneficial features.
• Method to produce lines of clones:

  1. choose the plant you want to clone based on its characteristics.
  2. remove several small pieces of tissue from the parent plant - you get the best results if you take tissue from fast-growing root or shoot tips.
  3. you grow the tissue in a growth medium containing nutrients and growth hormones - this is done under aseptic (sterile) conditions to prevent growth of microbes that could harm the plants.
  4. as the tissues produce shoots and roots they can be moved to potting compost to carry on growing.
• Animal tissue culture is often used in medical research because it means that you can carry out all kinds of of experiments on tissues in isolation.
• You can investigate the effect of glucose on cells in the pancreas by growing pancreatic cells in culture.
• Restriction enzymes recognise specific sequences of DNA and cut the DNA at these points - the pieces of DNA are left with sticky ends where they have been cut.