Variation, Evolution & Speciation

• Mendel did experiments with pea plants and had shown that the height characteristic of the pea plant is determined by separately inherited 'hereditary units' passed on from each unit
• Mendel reached 3 conclusions

  • characteristics determined by hereditary units
  • hereditary units are passed on to offspring unchanged from both parents
  • hereditary units can be dominant or recessive
• speciation

  development of a new species
• a species is a group of similar organisms that can reproduce to give fertile offspring
• speciation occurs when populations of the same species become so different they can no longer successfully interbreed to produce fertile offspring
• speciation diagram

  A) two populations of the same species

  B) populations seperated by physical barriers

  C) populations adapt to new environment

  D) development of a new species

  
• variation

  is the differences in the characteristics of individuals in a population, due to genetic differences
• two types of variation

  • genetic
  • environmental
• environmental variation

  • piercings
  • tattoos
  • dying hair colour
• genetic variation

  • eye colour
  • hair colour
  • height
• mutations introduce variation
• example mutation/natural variation (swordfish)

  • natural variation due to genetic mutations meant that some fish developed swords than others
  • the ones with swords would be able to get more food
  • this means they are more likely to survive and breed
  • they pass on the genes for swords to their offspring
• scientist who came up with theory of evolution

  Charles Darwin
• Charles Darwin theory

  all of todays species have evolved from simple life forms that first started to develop billions of years ago
• evolution

  is the process by which different kinds of living organisms change and develop overtime
• evolution occurs through a process called natural selection
• natural selection is when an organism is more at an advantage meaning they are ore likely to breed and reproduce passing it on to their offspring
• reasons of extinction

  • changes in environment
  • new predators
  • new diseases
  • new competitors
• reasons why Darwin's theory was originally controversial

  • religious beliefs
  • there wasn't enough evidence
  • he couldn't explain how the useful characteristics appeared or how they passed on
• Lamarck was another scientist and argued that changes an organism acquires during its lifetime will be passed on to its offspring