Darwin’sTheory of Natural Selection:A Mechanism For Evolution
Be careful not to suggest…  Organisms can acquire/change characteristics during their lifetime based on NEED  ...
Charles Darwin 1809 -1882“I have called this principle, by which each slightvariation, if useful, is preserv...
Important Features of Darwin’sTheory ofNatural Selection:A Mechanism forEvolution
1. Organisms produce more OFFSPRING than can possibly SURVIVE.
Thomas Malthus 1766-1834 What "struck" Darwin in Essay on the Principle of Populat...
REMEMBER… Overproduction (of Offspring)
2. As populations grow in size, NATURAL RESOURCES become limited. This forces organisms to COMPETE…
What do lions & hyenascompete for? Food Water Shelter – bear & raise young Space – hunt, travel
What else to lions competefor with other lions? Mates Do all lions mate?
REMEMBER… Competition
3. Becauseorganisms mustCOMPETE for limitedresources, theySTRUGGLE to EXIST.If they do not obtainneededresources, they____.
 VARIATIONS exist in all populations of organisms. The 2 causes of these differences can be attributed to: ...
Becauseorganisms arebuilt somewhatdifferently fromothers in thesame population,some have anADVANTAGE
What determines which variety offinch has a beak that will help itsurvive more successfully???
Adaptations make anorganism FIT for theenvironment. Fitness can be described as the ability to survive (out compete) an...
REMEMBER… Survival Of The Fittest
Environment createschallenges & opportunities Selective Pressures are applied to each population of organisms making...
REMEMBER… The environment applies a Selective pressure
5. Organisms that survive can pass on their traits to their offspring. They are able to REPRODUCE.
WHY?
Remember: Reproductive Advantage
How much change? Populations of organisms may change but not evolve into a new species. Evolution does not mean t...
REMEMBER… Darwin referred to this as: Descent with Modification
6. Over time,hundreds or thousands of generations, thecharacteristics (VARIATIONS) of a population change.
If members of the same species can no longer reproduce successfully (their offspring can reproduce), they are con...
REMEMBER… Speciation - Over time, members of a species may become SO different that they are now 2 d...
Overview1. Overproduction of offspring2. Competition for limited resources3. Variations exist which are inherited ...
Natural selection 2-12
of 29

Natural selection 2-12

Published on: Mar 3, 2016
Published in: Education      Technology      
Source: www.slideshare.net


Transcripts - Natural selection 2-12

  • 1. Darwin’sTheory of Natural Selection:A Mechanism For Evolution
  • 2. Be careful not to suggest…  Organisms can acquire/change characteristics during their lifetime based on NEED  These characteristics can only be passed on genetically.  Example: giraffes needed longer necks so they stretched them!
  • 3. Charles Darwin 1809 -1882“I have called this principle, by which each slightvariation, if useful, is preserved, by the termNatural Selection.”
  • 4. Important Features of Darwin’sTheory ofNatural Selection:A Mechanism forEvolution
  • 5. 1. Organisms produce more OFFSPRING than can possibly SURVIVE.
  • 6. Thomas Malthus 1766-1834 What "struck" Darwin in Essay on the Principle of Population (1798) was Malthuss observation that in nature plants and animals produce far more offspring than can survive, and that Man too is capable of overproducing if left unchecked. Malthus concluded that unless family size was regulated, mans misery of famine would become globally epidemic and eventually consume Man.
  • 7. REMEMBER… Overproduction (of Offspring)
  • 8. 2. As populations grow in size, NATURAL RESOURCES become limited. This forces organisms to COMPETE…
  • 9. What do lions & hyenascompete for? Food Water Shelter – bear & raise young Space – hunt, travel
  • 10. What else to lions competefor with other lions? Mates Do all lions mate?
  • 11. REMEMBER… Competition
  • 12. 3. Becauseorganisms mustCOMPETE for limitedresources, theySTRUGGLE to EXIST.If they do not obtainneededresources, they____.
  • 13.  VARIATIONS exist in all populations of organisms. The 2 causes of these differences can be attributed to: – Mutation – Meiosis (crossing-over, unique combination of chromosomes in egg/sperm)
  • 14. Becauseorganisms arebuilt somewhatdifferently fromothers in thesame population,some have anADVANTAGE
  • 15. What determines which variety offinch has a beak that will help itsurvive more successfully???
  • 16. Adaptations make anorganism FIT for theenvironment. Fitness can be described as the ability to survive (out compete) and reproduce. Why not just survive?
  • 17. REMEMBER… Survival Of The Fittest
  • 18. Environment createschallenges & opportunities Selective Pressures are applied to each population of organisms making it difficult for them to survive.
  • 19. REMEMBER… The environment applies a Selective pressure
  • 20. 5. Organisms that survive can pass on their traits to their offspring. They are able to REPRODUCE.
  • 21. WHY?
  • 22. Remember: Reproductive Advantage
  • 23. How much change? Populations of organisms may change but not evolve into a new species. Evolution does not mean that new species must arise, just that they can if enough changes take place.
  • 24. REMEMBER… Darwin referred to this as: Descent with Modification
  • 25. 6. Over time,hundreds or thousands of generations, thecharacteristics (VARIATIONS) of a population change.
  • 26. If members of the same species can no longer reproduce successfully (their offspring can reproduce), they are considered to be two distinct species.
  • 27. REMEMBER… Speciation - Over time, members of a species may become SO different that they are now 2 different species How does evolution really work?
  • 28. Overview1. Overproduction of offspring2. Competition for limited resources3. Variations exist which are inherited from their parents.4. Those more fit for the environment have a selective advantage5. Reproductive advantage6. Population characteristics may change