Unit 2 a ch 4 s2 evolution


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Unit 2 a ch 4 s2 evolution

  1. 1. Ch 4, Section 2: Evolution Standards: SEV2a, SEV3a, SEV3b, SEV3d
  2. 2.  What is Evolution?  Change in the traits of a population over a long period of time.  Evolution DOES NOT happen to an individual organism.  Evolution is the end result of natural selection.
  3. 3.  What is natural selection?  Darwin’s came to the conclusions:  All living things overproduce  There is variation among the offspring.  Variations in offspring and limited resources create struggle for existence.  Those with advantageous traits survive and pass on advantageous trait to offspring.  Those with negative traits die and take those traits out of the population.  Nature selects those that are most fit for the environment to survive.
  4. 4.  What is an adaptation?  Trait (physical or behavioral) that enables an organism to better survive in a particular environment.  Organisms are BORN WITH adaptations. Adaptations are GENETIC.  Organisms DO NOT acquire adaptations throughout their life.
  5. 5.  What is coevolution?  When two populations evolve due to a long-term interaction with each other.  EX: Lobelia flower has evolved pollen structures that rub the honeycreepers head as it feeds from the long curved flower with its long curved beak.  EX: Gazelles are fast to escape cheetahs. Only the fastest cheetahs will catch gazelles, eat, survive and pass on fast trait to offspring. Only the fastest gazelles will survive fast cheetahs and pass that onto their offspring.
  6. 6.  Can evolution happen by artificial selection instead of natural selection?  Yes!  This is how domesticated animals and plants have been “created.”  By selectively breeding two species with desirable traits we can get a different species.  Ex: We’ve bred corn to be larger, sweeter, easier to harvest. Teosinte was ancestral corn- look how selective breeding has changed it!
  7. 7.  Why should you care about evolution now?  Evolution of resistance is occurring with organisms that are able to create many new generations in a short period of time  Ex: bacteria & insects  Resistance makes an organism able to tolerate a chemical specifically designed to kill it.
  8. 8.  Is there a way to prevent insect resistance?  Typical scenario (diagram on left)  Pesticide sprayed on crop.  Most insects killed. Some are genetically adapted to resist pesticide.  These resistant insects survive & pass on resistance to offspring.  After many generations of reproduction the entire population is resistant.  If a farmer sprays most of his field and leaves a section unsprayed (a refuge) then more of the nonresistant will survive & breed with resistant and keep the population from becoming completely resistant. (diagram on right)