Final answer:
The statement that endospores are reproductive structures is not true. Endospores are dormant forms that bacteria form to survive unfavorable conditions, not for reproduction. Thus, the option D is the correct answer.
Step-by-step explanation:
Which of the following is not true of endospores? The statement that is not true is 'D) are reproductive structures'.
Endospores are indeed dormant structures formed by some bacteria, including Bacillus and Clostridium, not for reproduction, but for survival under adverse environmental conditions. The process of forming endospores, known as sporulation, results in a highly resistant structure that can withstand boiling, various chemicals, and extreme conditions, preserving the bacterial DNA until favorable conditions return. Sporulation does not lead to the degradation of the vegetative cell DNA; instead, the vegetative cell's DNA is replicated and sequestered within the endospore. Additionally, while Bacillus and Clostridium are two genera of bacteria known for producing endospores, they are not general terms for all endospores.