Final answer:
The correct statement is that organismal complexity is not related to the amount of DNA. DNA amount is relatively constant within a species but varies widely between species, and this variation does not correlate with organism complexity. The correct option is C.
Step-by-step explanation:
The true statement among the options provided is that organismal complexity is not related to the amount of DNA. This concept is known as the C-value enigma, which has shown that the amount of DNA does not correlate with the perceived complexity of an organism.
The genome size can vary widely between species that appear similarly complex, and even within single-celled organisms, there can be vast differences in genome size.
Furthermore, the amount of DNA between individuals within a species is indeed relatively constant, meaning that all humans have roughly the same amount of DNA. However, the specific sequence of that DNA varies from person to person, which is why we exhibit genetic diversity. This diversity is crucial as it serves as the raw material for evolution.
To address statement (d), it is noteworthy that the amount of DNA between species is not constant, emphasizing that DNA quantity does not necessarily predict species' complexity. Lastly, while it's true that closely related organisms have more homologous DNA sequences, this similarity is a reflection of their evolutionary relatedness rather than their complexity.