During the power stoke of muscle contraction, .

"do a testcross with a homozygous recessive plant."

substitution is the answer in this case

producers: apple trees, potatoes, carrots, grains, acorns, cabbage, grass, corn, lettuce

consumers: deer, mice, rabbits, chickens, squirrels, horses, worms, cows

predators: eagles, frogs, wolves, owls