2. There are several species of salamanders in Austin, Texas that have adapted for life in underground caves. These salamanders usually have small, non-functional eyes. Scientists studying biological evolution consider the salamanders' eyes to be an example of —. a. a vestigial organ
b. a genetic mutation
c. an analogous structure
d. an incomplete adaptation

Which of the following best describes the expensive tissue hypothesis? brains require more energy, so the gut had to be reduced, and larger brains and tool use led to higher quality diets. increasing body size means that homo neanderthalensis had to include more fat in its diet. brains require more energy, so the gut had to be reduced as brains got bigger. brains require more fat, so the gastrointestinal viscera (gut) had to expand, and hands were needed to acquire more food.