Evolution

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What is a Scientific Theory?

• In science, theories are statements or models
  that have been tested and confirmed many times.

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In science, the term Theory does not express
doubt

• They explain a wide variety of data and
  observations
• They can be used to make predictions
• They are not absolute, can be changed as new
  evidence is found

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Observations?Explanations

• Why do so many different animals have the same
  structures (the arm bones in a human are the same
  bones as a flipper in a whale)?
• Why is the sequence of DNA very similar in some
  groups of organisms but not in others?
• Why do the embryos of animals look very similar
  at an early stage?

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Key Points- Natural Selection

1. Variation exists among individuals in a species.
2. Individuals will compete for resources (food,
   mates, and space)
3. Competition would lead to the death of some
   individuals while others would survive
4. Individuals that had advantageous variations are
   more likely to survive and reproduce.

• This process came to be known as Natural
  Selection
• The favorable variations are called Adaptations

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Natural Selection

• Major means of evolution.
• Requires variation to operate.
• No variation means no traits to be selected for.

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A Simple Analogy

• Say in a species of blob.there exists blobs of
  all shapes and sizes (variation)

Blobs eat the little purple organisms that live
underground and on the surface.
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During a particularly hot year, food became less
abundant (competition), blobs that had the
ability to dig into the soil to get food had a
better chance of survival.
Many blobs died that year
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The ones that survived mated and passed their
genes to the next generation. (reproduction)
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The next generation had more blobs with the
pointed noses. That is NATURAL SELECTION!

• Variation
• Competition
• Survival
• Reproduction

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What is Artificial Selection?
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Assignment..

• In your group, I want you to make write a natural
  selection story! Pick a real or imaginary
  organism and incorporate these 4 things
• You have 5 minutes! Go!

• Variation
• Competition
• Survival
• Reproduction