BI 212 Unit 2 Vertebrate Nervous System, Sensory Systems and Movement 3. In a survey of brain formation of vertebrates, we see that as the animal becomes more complex, the complexity of the brain also increases. The hindbrain appears to be very large in fish and amphibians as compared to the cerebrum. The cerebrum seems to be most developed in these animals for sight smell and or hearing. Hypothesize why the hindbrain is so large in proportion to the cerebrum and why the cerebrum is so small in these animals. Why would the cerebrum need to be better developed in mammals? Explain your answer. In general, would you expect the cerebrum to be better developed in mammals that were predators or prey? Explain your answer.