Evolution

• What is evolution?


  • A gradual change in the inherited traits within a population over time
  • Occurs due to natural selection
• Outline the theory of natural selection

  1. Genetic variation exists due to spontaneous mutations
  2. Selection pressures (e.g. competition, disease) exist
  3. Random mutation gives an organism a selective advantage
  4. Organism is better adapted to the environment and survives
  5. Organism reproduces, passing on its beneficial alleles
  6. Frequency of advantageous alleles increase
• Why does competition between organisms in a habitat exist?


  The resources within a habitat required for survival are limited
• Give some examples of competition between organisms within a habitat


  Competition between animals for food, shelter, mates etc.

  Competition between plants for light, water, minerals etc.
• Describe how antibiotic resistance in bacteria can be used as an example to illustrate the process of evolution

  1. Genetic variation exists due to spontaneous mutations
  2. Antibiotics act as a selection pressure
  3. Mutations gives a bacterium antibiotic-resistance
  4. If an antibiotic is administered, the bacterium is better adapted and survives, whilst other bacteria are killed
  5. Bacterium reproduces, passing on its resistant variant
  6. Frequency of antibiotic-resistant allele increases
• Why is the development of antibiotic resistance in bacteria a good study for evolution?

  Bacteria reproduce very rapidly, allowing the first-hand observation of evolution
• How can the observation of fossils provide evidence for evolution?

  • Older fossils (found in rocks deeper in the ground) contain simpler organisms. Newer fossils (found closer to the surface) contain more complex organisms. Comparisons of fossils show that simple organisms evolved into more complex life forms.
  • Fossils can be organised into chronological order, allowing the changes in organisms over time to be observed
• What fossils have provided evidence for human evolution? 


  • 'Ardi' - 4.4 million years old
  • 'Lucy' - 3.2 million years old
  • Leakey discovered 1.6 million year old fossils
• What clues does 'Ardi' give scientists about human evolution?


  Female hominid fossil. She shows phenotypic traits which encompass characteristics of both humans and apes:

  • Ape-like characteristics e.g. long arms, large big toes
  • Human-like characteristics e.g. the structure of her bones suggests that she walked upright
• What clues does 'Lucy' give scientists about human evolution?

  Female hominid fossil. She shows phenotypic traits which are more human-like than that of 'Ardi'

  • The structure of bones in her legs and feet are more adapted to walking than climbing
  • However, her brain size is closer to that of an ape's
• How did Leakey's findings provide evidence for human evolution?

  He discovered many hominid fossils.

  The 1.6 million year old fossil 'Turkana Boy' showed traits comparable to that of modern-day humans e.g. similar brain size.
• How has the development of stone tools provided evidence for evolution?

  • Correlation between the development of more complex tools and an increase in brain size
  • Primitive tools are older than more complex tools. Brain size has increased over time.. as brain size increased, advancements in tool use were made.
• Describe the methods used by scientists to date tools

  • Carbon-14 dating - estimating the age of carbon-containing material that is found in tools (e.g. wooden handles) or alongside tools (e.g. fur)
  • Stratigraphy - using the age of the layers of sediment surrounding the tool as an indication of the age of the tool