Horses and donkeys can breed and produce sterile offspring known as mules. Horses and donkeys remain separate species because of this hybrid sterility, which is:

A. an allopatric barrier to reproduction.
B. a sympatric barrier to reproduction.
C. a prezygotic barrier to reproduction.
D. a postzygotic barrier to reproduction.


Answer: D. a postzygotic barrier to reproduction.

Biology & Microbiology

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The tapetum lucidum is a key adaptation for

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The difference between microevolution and macroevolution is that

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Some adults with attention deficit hyperactivity disorder (ADHD) have abnormally low activity of the neurotransmitter involved in pleasure, attention, memory, sleep, movement, and learning, which increases their risk of drug abuse

Which drug are they most likely to abuse? A) cocaine B) morphine C) codeine D) alcohol

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