Evolution by Natural Selection

• How many different species of animals and plants are there on Earth?

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

  One percent
• 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, like 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 advantage do rabbits with thicker fur have in a colder environment?

  They are more likely to survive
• What happens to the alleles for thicker fur over many generations?

  They become more common in the population
• How does the introduction of a predator affect rabbit populations?

  Rabbits with better eyesight or hearing survive
• What is the definition of evolution provided in the video?

  Change in inherited characteristics over time
• What occurs when two populations of one species become so different?

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

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

  They are too different in phenotype
• What are the key points of natural selection as described in the video?

  • Genetic variation exists within populations
  • Environmental changes favor certain traits
  • Beneficial traits increase survival and reproduction
  • Over generations, these traits become more common
• What are the implications of speciation as discussed in the video?

  • Two populations can no longer interbreed
  • They evolve into separate species
  • Genetic differences accumulate over time