Figure 1.1 The Many Faces of Life The processes of evolution have led to the millions of diverse organisms living on Earth today. Prokaryotic archaea (A) and bacteria (B) are all single-celled organisms, as described in Chapter 25. (C) Many protists are unicellular but, as discussed in Chapter 26, their cell structures are more complex than those of the prokaryotes. This protist has manufactured “plates” of calcium carbonate that surround and protect its single cell. (D–F) Most of the visible life on Earth is multicellular. Chapters 27 and 28 cover the green plants (D). The other broad groups of multicellular organisms are the fungi (E), discussed in Chapter 29, and the animals (F), covered in Chapters 30, 31 and 32.