Fish respiratory systems exchange gas and receive oxygen at the gills. this oxygen then enters the blood stream and is pumped through the heart and back through the gills without first returning to the heart. this order of events best describes which type of circulation system?
a) double loop
b) single loop
c) open
d) recycling

Why do you think the puppy litter was all dark-haired?

Works together in the synthesis, modification, packaging, and transport of lipids and proteins

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.