Why a drop of fat in a unicellular algae makes the algae float. Let one hypothesize, while the other analyzes them.

The buoyancy of the body depends on weight, density. Fat is less dense than water, so fat increases the body’s buoyancy.
Fat is an adaptation in algae that slows down sinking.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.