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Natural and Artificial Selection

Natural and Artificial Selection. Grade 11 Biology SBI3U. Adaptation. A characteristic or feature of a species that makes it well suited for survival or reproductive success in its environment. Adaptation. Explains why the cactus can be successful in the desert. Survival of the Fittest.

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Natural and Artificial Selection

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  1. Natural and Artificial Selection Grade 11 Biology SBI3U

  2. Adaptation • A characteristic or feature of a species that makes it well suited for survival or reproductive success in its environment

  3. Adaptation • Explains why the cactus can be successful in the desert

  4. Survival of the Fittest • Herbert Spencer • This phrase has been used to describe Darwin’s theory • Is this misleading?

  5. Types of Selection • Directional Selection • Stabilizing Selection • Disruptive Selection • Sexual Selection

  6. Directional Selection • Selection that favours an increase or decrease in the value of a trait from the current population average

  7. Directional Selection

  8. Stabilizing Selecton • Selection against individuals exhibiting traits that deviate from the current population average

  9. Stabilizing Selection

  10. Disruptive Selection • Favours two or more variations of a trait that differ from the current population average

  11. Disruptive Selection

  12. A Human Example • Some populations have adapted to living at extreme heights • Able to survive despite low oxygen levels

  13. Sexual Selection • The favoring of any trait that specifically enhances the mating success of an individual

  14. Artificial Selection • A controlled, captive breeding process • Occurs in captivity rather than in the wild • Humans choose which individuals to breed that demonstrate a favorable trait

  15. The Process of Artificial Selection • 1) Choose a species that can be bred in captivity • 2) Breed a large number of individuals • 3) Choose a trait that you wish to favour • 4) Identify individuals that exhibit this trait most strongly • 5) Breed only these individuals to produce the next generation • 6) Repeat steps 4 and 5 over many generations

  16. Artificial Selection in Plants • Domestic crops are bigger and heartier than wild • Why might this be important? • Selection process takes place over thousands of years – beginnings in the Fertile Crescent

  17. The Candy Experiment • Pick your favorite flavour out of the bag

  18. The Candy Experiment • Pick your favorite flavour out of the bag • Now look at what’s left • We have selected for favorable traits in our food

  19. Artificial Selection in Animals • In animals, there are a number of features we many consider

  20. Artificial Selection in Animals • In animals, there are a number of features we many consider • Size • Muscle Mass • Fattiness • Temper

  21. Our Best Friend • Wolves were among the very first domesticated animals • What did we select for in wolves?

  22. Our Best Friend • What did we select for in wolves? • Lack of aggression towards humans • Lack of fear towards humans • Territoriality towards others • Loyalty

  23. Our Best Friends • We have selected for many traits in dogs • Size • Colour • Aggression • As a result we have many breeds today

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