Multiple Choice
Which of these organisms is a primary producer?
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1. Introduction to Biology
Introduction to Biology
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Which of the following is the most abundant element in the human body by mass?
A
Carbon ($C$)
B
Hydrogen ($H$)
C
Nitrogen ($N$)
D
Oxygen ($O$)
Verified step by step guidance1
Understand the context: The question asks about the most abundant element in the human body by mass. This requires knowledge of the composition of the human body and the relative abundance of elements.
Recall that the human body is primarily composed of water ($H_2O$), which makes up about 60% of body weight. Since water contains oxygen ($O$), this element contributes significantly to the body's mass.
Consider the molecular weight of water: Oxygen ($O$) has a much higher atomic mass (approximately 16 atomic mass units) compared to hydrogen ($H$), which has an atomic mass of approximately 1 atomic mass unit. This means oxygen contributes more to the mass of water.
Evaluate the other elements listed: Carbon ($C$), hydrogen ($H$), and nitrogen ($N$) are also important in the human body, but their contributions by mass are smaller compared to oxygen. For example, carbon is a key component of organic molecules, but it is less abundant by mass than oxygen.
Conclude that oxygen ($O$) is the most abundant element in the human body by mass due to its significant presence in water and its higher atomic mass compared to other elements.
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