NATURAL SELECTION IN ACTION

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CHAPTER 5

• Section 3
• NATURAL SELECTION IN ACTION

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INSECTICIDE RESISTANCE

• Farmers use a wide variety of chemical
  insecticides to protect their crops.
• However, some insecticides that worked well in
  the past are no longer as effective.

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GENERATION TIME

• Insects quickly develop resistance to
  insecticides because they produce many offspring
  and usually have short generation times.
• GENERATION TIME- is the period between the birth
  of one generation and the birth of the next
  generation.
• LOOK AT FIGURE 16 ON PAGE 118.

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ADAPTATION TO POLLUTION

• Before pollution the dark peppered moth stood
  out against the light backgrounds and as a
  result were eaten more frequently.

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• After the pollution, the light peppered moth
  stood out against the dark backgrounds and as a
  result were eaten more frequently.
• So the dark moths survived and produced more dark
  offspring.

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FORMATION OF A NEW SPECIES

• A portion of a species population can become
  separated from the original population. Over
  time, the two populations can become so different
  that they can no longer interbreed. This process
  is called SPECIATION. One way speciation can
  occur is shown in the following 3 steps.

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1) SEPERATION

• A portion of the population becomes isolated.
  Examples could be the formation of a canyon,
  mountain range, or lake.

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2) ADAPTATION

• If a population is divided, the environment may
  also change.
• Over many generations, the separated group may
  adapt to better fit their environment.

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3) DIVISION

• After many years (hundreds, thousands, or
  millions) the two populations are so different
  that they can no longer interbreed.they are NO
  LONGER the same species.