Algae because it is a small organism that the larva state of animals live in and feed on it
Water, sunlight, air, nutrients
" Earth is a living planet because it contains organisms. Life exists on Earth on the land, in the water, in the atmosphere. An organism that uses solar or chemical energy to produce "food" by making inorganic compounds into complex organic molecules. " (Quizlet)
Hope this helps
Because you need your legs to carry your whole body, so, essentially, your legs have to have bigger bones and muscles.