Natural Selection Notes

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Natural Selection Notes

  1. 1. How Does Evolution Happen? (Natural Selection)
  2. 2. First man to explain o Charles Darwin o Took a five year voyage around the world after he got out of college o Served as a naturalist on the British ship HMS Beagle o Formed a theory of how evolution happened o Collected plant and animal samples on his travels o Visited the Galapagos islands just west of Ecuador (South America)
  3. 3. Map of the Galapagos Islands
  4. 4. Galapagos Island Discoveries o Found that the finches on these islands were similar to Ecuador’s o Each island was still a little different from the next o Found that the beaks of the finches had adapted to their food source on the different islands.
  5. 5. Finches
  6. 6. Darwin starts to think.. o How did we get these similar species? o He had ideas about the Earth o He found that Earth has been formed by natural processes over a long period of time o He had ideas about breeding o Selective breeding- breeding plants/animals to have desired characteristics o He had ideas about populations o Realized that any species can produce many offspring, but they are limited by several factors.
  7. 7. What limits offspring? o o o o Starvation Disease Competition Predation Four factors that limit offspring o He found that really only a limited amount of individuals will survive to reproduce. o There is something unique about the survivors. They must have stronger genetic traits. Those are the traits that will pass down to their offspring.
  8. 8. Darwin’s thinking lead to his theory of Natural Selection o Once he returned from his voyage, he thought for 20 yrs about the observations he had taken from the world and wrote a book called On the Origin of Species by Means of Natural Selection. o Darwin’s theory of natural selection is the process by which individuals best adapted to their environments survive and reproduce more successfully than less well adapted individuals o This theory of natural selection is broken into four parts.
  9. 9. Four Parts of Natural Selection o 1) Overproduction oOrganisms will give birth to thousands of offspring realizing that some will become adults and others will not. o 2) Inherited Variation oEvery individual has its own combo of traits. (similar to parents)
  10. 10. Continued o 3) Struggle to Survive oPredators, starvation, diseases o 4) Successful Reproduction oThe organisms best adapted in their environment will produce the most surviving offspring.
  11. 11. Think About it…
  12. 12. Darwin Lacked o When Darwin was introducing his theory of natural selection he lacked two important things: o 1- He didn’t know how we inherit traits o 2- He didn’t know how the variations occurred o We have learned how both of these occurrences happen, tell me how!
  13. 13. Yes?? o 1) We inherit traits from our parents when they get passed down to the offspring. o 2) Variations occur because of the different gene combinations that can be made when the mother and father come together to produce offspring.
  14. 14. Natural Selection in Action o A population changes in response to its environment. o Things that can affect an environments population are: o Hunting o Resistance o Competition
  15. 15. Hunting o A new affect such as hunting can play a role in how a population level rises or falls. o In 1930 Uganda’s male elephant population that contained tusks was 99% and only 1% of them were born without them. Today 85% of male elephant population contains tusks. o Because of this, more of the tusk less elephants are surviving and reproducing. This trait does get passed down.
  16. 16. Resistance o Some organisms such as insects can build resistance to certain chemicals. o This can send an increase in a particular insects population that could be harmful. o It doesn’t take long for insects to build up this resistance and reproduce. o Generation time: the period between the birth of one generation and the birth of the next generation.
  17. 17. Competition o Many species will have competitions for their mates o Some organisms may over time have some interesting adaptations. o Feather colors, smells, dances, sounds, etc.
  18. 18. Forming a New Species o May form if the groups get separated from the original population. o The two groups can adapt to their environments and get to a point where they are so different they can’t even mate anymore. o A new species is a result of evolution. We call this speciation. o Separation-Adaptation-Division

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