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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Signs of depression include feeling sad most of the time for 2 weeks or longer; loss of interest in things normally enjoyed; lack of energy; sleep and appetite disturbances; weight changes; feelings of hopelessness, helplessness, or worthlessness; an inability to make decisions; and thoughts of death and suicide.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.
More than one-third of adult Americans are obese. Diseases that kill the largest number of people annually, such as heart disease, cancer, diabetes, stroke, and hypertension, can be attributed to diet.
Serum cholesterol testing in adults is recommended every 1 to 5 years. People with diabetes and a family history of high cholesterol should be tested even more frequently.