Natural Selection

Sickle Cell Anemia

Charles Darwin's Theory

  • the animals best suited to the environment live longer
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Jean Lamarck's Theory

  • adapted to environment
  • giraffes once had short legs and necks but grew because of food being so high up
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Alfred Russel Wallace's Theory

  • weaker animals won't adapt
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What is sickle cell anemia?

Sickle cell anemia occurs when your blood cell is crescent shaped rather than circular, causing it to block blood flow to limbs and organs.

Why is sickle cell anemia more common in African Americans?

Scientists think that sickle cell anemia mostly occurred where there was a lot of cases of malaria. People with sickle cell anemia are protected from malaria because the sickled shape of the blood cell prevented the malaria organism from getting into the blood.
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