You enter a crime scene and discover one, single blood drop. You immediately measure the drop and calculate it's Impact Angle. However, you will not be able to determine the Point of Origin of this single blood drop. Why can't you determine the Point of Origin from a single blood drop?

the population of unionid mussels in the hudson river decreased after zebra mussels were introduced. zebra mussels, a nonnative species, competed with the unionid mussels for food. the zebra mussels were able to outcompete the unionid mussels, allowing the zebra mussel population to increase dramatically over six years. the unionid mussel population decreased due to a lack of food.

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