Ashell is composed of three layers? - list and describe each layer.

Three layers:

(uncalcified)-An outer proteinaceous periosteum,

(calcified)- a primatic layer,

(calcified)- and an inner pearly layer of nacre.

8

explanation:

4+4=8

within these regions are all the major types of biomes in the world. a biome is a community of animals and plants spreading over an extensive area with a relatively uniform climate. some diverse biomes represented in north america include desert, grassland, tundra, and coral reefs.