What chemical ion is responsible for initiating the contraction of a muscle fiber?

What is the relationship between absorbance of light and the rate of photosynthesis?

When the oxygen produced by photosynthetic plants in the water dissolves in the water, which of these is being formed?

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.