The excretory system in mammals consists of the following parts except

Analyze the question: You are asked which part is NOT in the mammalian excretory (urinary) system. Three options are real parts and one is not.

Concept: The mammalian urinary system is made up of:

• Two kidneys, which filter blood and form urine
• Two ureters, which carry urine from each kidney to the bladder
• One urinary bladder, which stores urine temporarily
• One urethra, which carries urine out of the body

Step-by-step solution:

• A. Two kidneys: correct, mammals have a pair of kidneys. This is part of the system.
• B. Two ureters: correct, one leaves each kidney. This is part of the system.
• C. Two bladders: incorrect. Mammals have only one urinary bladder, so this is the exception.
• D. One urethra: correct, a single tube carries urine out of the body. This is part of the system.

Answer: The exception is C. two bladders.

Exam tip: Remember the pattern 2-2-1-1: 2 kidneys, 2 ureters, 1 bladder, 1 urethra. In "except" questions, look for the option whose number is wrong. Here, the bladder is single.