Which of the following is true of species interactions? a) they can act as agents of natural selection. b) the outcome of any species interactions is static through time. c) they do little to affect species distributions. d) they cannot affect species abundance.

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.