The following is an excerpt from the case study "It's All Greek to Me," where Mr. Stamos is describing the symptoms shown by his daughter, Nikoleta: "Nikolaus tells Dr. Stephens that ... his daughter continues to suffer from general malaise and lethargy, and her skin looks a little pale recently. Nikoleta's parents also tell the doctor that their daughter ... seems tired and cranky." Define anemia and explain how it caused each of Nikoleta's symptoms.