How does the energy in food become available to organisms?

The consumed food first need to be physically broken and after that chemically. The energy stored in food (food contains carbohydrates, fats, proteins, water, vitamins, and minerals) is released when chemical bonds of molecules in food are broken in metabolic processes such as cellular respiration.  Cellular respiration might be aerobic (involves the chemical reaction of food molecules with molecular oxygen)  or anaerobic (without additional oxygen).

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.