Malthus didn't account for diseases or natural disasters in his theory of population growth.
The Griffith's experiment, the Avery-MacLeod-McCarty experiment, and the Hershey–Chase experiments were the set of experiments that established DNA as the key hereditary molecule. The Avery-MacLeod-McCarty experiment was an extension to the Griffith's experiment. The heat killed virulent S strain cells of the Griffith's experiment were lysed to form a supernatant containing a mix of RNA, DNA, proteins and lipids from the cell. The supernatent was equally divided into 3 parts after the removal of the lipids. The 3 parts were respectively treated with an RNAase to degrade the RNA, DNAase to degrade the DNA and proteinase to degrade the proteins. The treated supernatant was then added into the culture containing the non-virulent R cells. In case of the supernatant treated with the DNAse, no transformation of R cells into S cells occurred. The transformation of R cells to S cells occurred in the proteinase and the RNAse cases. This indicated that DNA was the hereditary molecule and not protein or RNA.

I believe Tom is mot likely suffering from the post traumatic stress disorder.Post traumatic stress disorder is the mental health condition that is triggered by a terrifying event-either experiencing it or witnessing it. Symptoms may include flashbacks, nightmares and severe anxiety, as well as uncontrollable thoughts about the event.
No, because two creatures with similar niches can evolve similar traits and appearances despite not having a common ancestor.