Evolution by Natural Selection

• What should you be able to describe by the end of the video?

  What's meant by evolution
• How does evolution take place according to the video?

  Through natural selection
• How many different species of animals and plants are estimated to exist on Earth?

  Nearly 9 million
• What percentage of species that have ever lived on Earth are currently extinct?

  99% of the total species
• How long ago did life first develop on Earth?

  More than 3 billion years ago
• What were the first life-forms on Earth described as?

  Very simple, for example, single cells
• What is the process called where all species of living things have evolved from simple life forms?

  Evolution by natural selection
• What is an example of genetic variation mentioned in the video?

  Rabbits having different combinations of alleles
• What happens to rabbits with alleles for thicker fur in colder temperatures?

  They are more likely to survive and reproduce
• What is the outcome for the rabbit population over many generations when thicker fur is advantageous?

  The alleles for thicker fur become more common
• What advantage do rabbits with better eyesight or hearing have when a predator moves into the area?

  They are more likely to detect the predator
• What happens to the alleles for better eyesight or hearing over many generations?

  They become widespread in the rabbit population
• What is the definition of evolution as stated in the video?

  The change in inherited characteristics of a population over time
• What can happen when two populations of one species become so different in phenotype?

  They can no longer interbreed to produce fertile offspring
• What is an example of two different species mentioned in the video?

  Normal-sized rabbits and pygmy rabbits
• Why can't pygmy rabbits breed successfully with normal-sized rabbits?

  They are so small that they cannot interbreed
• What is the process of natural selection?

  • Variation exists within a population
  • Some traits provide advantages in survival
  • Individuals with advantageous traits are more likely to survive and reproduce
  • These traits are passed on to offspring
  • Over generations, advantageous traits become more common
• What are the implications of speciation in populations?

  • Two populations can become distinct species
  • They may no longer interbreed
  • Genetic divergence occurs over time
  • Leads to biodiversity