Evolution

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Evolution
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I. Variation and Adaptation

1. Species are interbreeding populations of
   organisms which produce viable offspring.

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B. Niche

• An organisms niche is the place it survives and
  the role the organism plays in the environment.
• 2. Niches include all the environmental factors
  to which populations are adapted (living and
  non-living)

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C. Adaptation

• If the niche changes, then the organism must
  move, change (adapt) or die
• 2. Adaptation is an inherited trait which
  increases a organisms chance of survival and
  reproduction.

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D. Variation

1. Variation is the differences among members of a
   population.
2. Increased variation in a population increases a
   populations chance of survival
3. Inherited variation is a change in genome cause
   by mutation or the recombining of the genetic
   code.

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E. Sources of Genetic Variation

• 1. Mutation- change in the sequence of DNA
• May change an organisms phenotype
• Random change
• 2. Sexual Reproduction- Gene Shuffling
• - Chromosome segregation and crossing-over

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Examples

• In the desert, animals are brown and white and
  generally blend in with the sand. What would
  happen to a population of bright red bugs?
• In the snow, animals tend to be white and light
  colors. What would happen to a red fox?
• In the heat of the desert, could a polar bear
  survive?

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Artificial Selection

• Artificial selection occurs when humans select
  the best traits for plants and animals
• Examples
• Disease-resistant crops
• Beefy cattle
• Cows that produce more milk

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Adaptations
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Types of Adaptations

• Mimicry Organisms that copy the appearance of
  another species for protection

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Types of Adaptations

• Camouflage When an organism blends in to its
  surroundings

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Variation within a species increases the
likelihood that at least some members of a
species will survive under changed environmental
conditions.
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Evolution

• Evolution means a change over time or descent
  with modification
• It occurs in populations, not individuals in
  response to environmental pressures
• Natural selection is the mechanism of evolution
  (the way it happens)

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Natural Selection

• Natural selection happens because
• 1. Overproduction organisms produce more
  offspring than can survive
• Fun Facts A fern plant may produce 50 million
  spores each year. If they all survived, in the
  second year they would nearly cover North
  America. An oyster may shed 114,000,000 eggs in a
  single spawning season. If they all survived, the
  ocean would be literally filled with oysters.

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Natural Selection

• 2. Variation Within a population there are many
  differences between organisms. These differences
  are inherited.
• Examples
• Color in flowers
• Length of antlers in elk
• Height in humans
• Shape of beak in birds

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Natural Selection

• 3. Struggle for existence There are limited
  resources, so living things must compete against
  each other to stay alive
• 4. Survival of the fittest Only the organisms
  best adapted to the environment will live

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Natural Selection

• 5. Populations evolve Over time, the favorable
  adaptations are passed on and the entire
  population changes