Why are some amino acids called "essential amino acids"?

Which of these resources is used worldwide to make construction products, pottery, and porcelain

In terms of alternation of generations, the internal parts of the pollen grains of seed-producing plants are most similar to a ) moss sporophyteb) moss gametophyte bearing both male and female gametangiac) fern sporophyted) fern gametophyte bearing only antheridia

Photosynthesis converts solar energy into what type of energy?