Biology Now, 2e

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Cells dramatically range in size, and viruses are even

smaller. The amoeba, a single-celled eukaryote that eats

smaller unicellular organisms, is visible under a light

microscope. But to observe a virus, one would have to use

an electron microscope, which relies on a high-voltage

beam of electrons to magnify an image.

Sizing Up Life

500 μm

Amoeba proteus

130 μm

Human egg cell

(shown next to an Amoeba proteus)

30 μm

Skin cell

(shown next to a human egg cell)

8 μm

Red blood cell

(shown next to a skin cell)

.1 3 μm

Influenza virus

(shown next to a measle virus)

.0 3 μm

Rhinovirus

(shown next to an influenza virus)

3 μm

E. coli bacterium

(shown next to a red blood cell)

.2 2 μm

Measle virus

(shown next to an E. coli bacterium)