Describe two ways in which yeasts are useful to humans.

Yeasts are useful to humans as they have many industrial and domestic value as explained under:

1) Yeasts are used in baking of bread.

2) Yeasts are used in fermentation of wine.

3) Yeasts are used in probiotic drinks that boost our immunity by maintaining healthy functioning of gastrointestinal tract.

4) The ability of the yeast to ferment ethanol have been used in industrial applications to yield ethanol as fuel.

5) As an ingredient in different anti fungal medicines.

i think the answer is

mass

only about ten percent of the energy at one trophic level is passed on to organisms at the next trophic level. the remainder of the energy is used in life processes or lost as heat.