Topic 4

• Variation

  Differences between individuals
• Causes of variation

  • Genetic variation (inherited variation)
  • Environmental variation (acquired characteristics)
• Some characteristics are caused a combination of genetic and environmental variation
• Charles Darwin

  • Spent 5 years travelling around the world on the HMS Beagle
  • Studied plants and animals and noticed variation in members of the same species and that those characteristics most suited to the environment were more likely to survive
  • Noticed characteristics could be passed onto offspring
  • Wrote the theory of evolution by natural selection
• Natural selection

  'Survival of the fittest' - the organisms which are best adapted to their environment will survive, reproduce and pass the genes for those useful features on to their offspring
• Darwin's Theory of Natural Selection by Evolution

  1. Individuals in a population show variation in their characteristics due to differences in their genes

  2. Some individuals have characteristics which make them better adapted to survive selection pressures in their environment

  3. The individuals which are best adapted to their environment will survive, reproduce and pass the genes for those useful features on to their offspring

  4. Evolution is how organisms have changed and become better adapted to their environment over many years
• Antibiotic resistant bacteria

  Resistant (unaffected) to antibiotics
• Antibiotic resistant bacteria

  • Methicillin-resistant Staphylococcus aureus (MRSA)
• How bacteria have developed resistance to antibiotics

  1. There is variation in the bacterial population

  2. One bacterium develops a mutation by chance that means it is resistant to an antibiotic

  3. The antibiotic kills some of the bacteria

  4. The resistant bacterium is better adapted, survives and reproduces

  5. The resistant bacterium has multiplied and no longer have competition from the other bacteria

  6. The person is likely to feel ill again and the antibiotic won't work

  7. The bacterium has evolved
• Reduce development of superbugs: Do not over-prescribe antibiotics (only used when they are really needed), Complete their courses of antibiotics, even if they start to feel better
• Ardi

  • Female human-like fossilised skeleton that dates from 4.4 million years ago
  • Had a chimp's brain size and feet that climbed trees
  • The bones that make up Ardi's feet suggest that humans and chimpanzees evolved separately
• Lucy

  • Female human-like fossilised skeleton, and dates from 3.2 million years ago
  • Skull suggested brain bigger than Ardi
  • The bones in the feet showed an arch suggesting she walked in an upright position, like a human
• Leakey's discovery of a skeleton

  • 1.6 million years old (Turkana boy)
  • Had human brain size and he walked upright (from the foot bones)
  • Fossils showed humans evolved from apes – they became better at walking upright, larger brains and had arm/leg structure more like a human
• Evidence for human evolution

  • Structure of stone tools - tools have become more complex over time indicating humans have larger brains (larger skulls) and are more intelligent
  • Dating stone tools from the environment - the deeper layer the tool is found in the rock, the older it is
  • Use carbon 14 dating – to date any carbon-containing material found with the tools
• Linnaean Classification System

  • kingdom - animal
  • phylum - chordata
  • class - mammal
  • order - carnivorous
  • family - felidae
  • genus - panthera
  • species - leo
• Genetic analysis

  • Led to the suggestion of the three domains: 1) eukarya (plants, animals, fungi, protists) 2) bacteria 3) archaea (bacteria living in high temperatures and make methane)
  • Genetic techniques to determine the DNA base sequence to compare genes of organisms – the more similar the sequence in the gene, the more closely related the organisms are
• Roughly 10,000 years ago humans started farming animals
• Auroch

  One of the first animals farmed, gathered into herds and over hundreds of years the ones that produced the most meat and milk were allowed to breed, now extinct but its descendants, the modern cow is one of the most farmed animals on the planet
• Selective breeding

  1. Humans choose the individuals (animal or plant) with useful features, breed them together and the offspring are likely to inherit those useful features

  2. This process is repeated over several generations to get the individual with as many useful/desired features as possible

  3. Different varieties of plants and animals with desired characteristics can be developed by selective breeding
• Selective breeding

  • cows that produce lots of milk
  • chickens that produce large eggs
  • wheat plants that produce lots of grain
• Advantages of selective breeding

  More likely to get the desirable characteristic
• Disadvantages of selective breeding

  • There is less variation which reduces the gene pool - the number of genes (alleles) available to breed from
  • More likely to have genetic health problems
  • More susceptible (likely to catch) a new disease