What would a biologist say is the role of nutrients in an ecosystem?

Nutrients are elements from which organisms construct the molecules of life.

Explanation:

Nutrients are chemicals necessary in any ecosystems for organisms to effectively grow, survive and decompose.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.