B5.2 evolution and natural selection

• natural selection is known as survival of the fittest. the best adaped organsims survive
• the most useful alleles get passed down from parents to their offspring
• scientists have used fossils to look at how organisms have evolved over time
• natural selection is a process in which a species changes over time in response to change in the environment or competition between organisms in order for the species to survive
• evolution suggests that different species have evolved from simpler life forms
• evolution suggests organisms that are able to survive are those that have adapted best to their environment
• evolution is a slow process that can take thousands and millions of years to happen
• scientists have used fossils to look evidence to look at how organisms have adapted over millions of years and how their characteristics have changed
• if a species is unable to adapt quickly enough to its environment, then it is at risk of becoming extinct
• extinction can happen for various reasons:

  • new predators
  • new diseases
  • habitat destruction
  • environment change
  • increased competition for resources
• adaption leads to the formation of new species
• What is evolution?

  Evolution is the process by which small changes in organisms occur over long periods of time.
• How is a species defined?

  A species is a group of organisms that can interbreed to have fertile offspring.
• What drives evolution?

  Natural selection drives evolution.
• What are the steps in evolution?

  1. Variation exists in every population, some of which is inherited.
  2. Organisms with the best adaptations are most likely to survive and reproduce (natural selection).
  3. Inheritance means adaptations are likely passed to offspring.
  4. Less well-adapted organisms are less likely to pass on their adaptations.
  5. Over generations, small differences lead to the formation of new species.
• What causes variation in a population?

  Variation can be caused by small changes in DNA called mutations.
• What are the effects of mutations on variation?

  Most mutations have no effect, some are advantageous, and some are disadvantageous.
• How do adaptations influence survival and reproduction in natural selection?

  Individual organisms with the best adaptations are most likely to survive and reproduce.
• What does inheritance mean in the context of evolution?

  Inheritance means these adaptations are likely to be passed to offspring.
• What happens to less well-adapted organisms in terms of adaptation inheritance?

  Less well-adapted organisms are less likely to pass on their adaptations.
• Over many generations, what is the outcome of small differences in organisms?

  These small differences add up to the formation of new species by evolution.