EK Biology, In-Class Exams, Lectures 2 and 3 Lecture 2 Question 33. Intron sequences of identical genes in closely related species are often very different. Which of the following is most strongly suggested by this evidence? A. Identical genes in closely related species may code for diff proteins B. eliminated C. Intron sequences are heavily characterized by selective pressure D. Selective pressure has little or no role in the development of intron sequences. I don't understand this question or its answer/explanation. I only was able to eliminate B and guessed. Lecture 3 Question 53 - Which of the following statements does not contradict information in the passage concerning C. botulinum? A. eliminated B. eliminated C. A glass containing C botulinum may be disinfected by immersion in boiling water. D. Animals have no natural defense against the neurotoxin produced by C. botulinum I eliminated A and B. I picked D because I felt C was not really supported by the passage. If you look C. botulinum has a D value ["D value is the time required to kill 90% of microorganisms or spores in a sample at a specified temperature"] at 121 degrees Celsius of 0.20. Water boils at 100 degrees Celsius, so can we assume boiling water will actually disinfect C. botulinum? D is an extreme answer choice ("no natural defense"...) and some info in the passage sort of indicates that D is not true. However as both C and D seem to have flaws/problems I don't know how you know which one is right. Thoughts?