Biology Now, 2e

Navel Gazing ■ 279

Q1: From the prokaryotic structures shown in Figure 15.7, what shape would you assign to

drawing number 8 in van Leeuwenhoek’s illustration?

Q2: Which of the large prokaryote drawings has the coccus shape?

Q3: Do you think all of these “animalcules” drawn by van Leeuwenhoek are prokaryotes? Why or

why not?

Figure 15.11

The first illustrations of microbes

Antonie van Leeuwenhoek’s descriptions and illustrations of microscopic life led to his being considered

the “father of microbiology.”

atmosphere is 78 percent nitrogen—and convert

it to ammonia, making it available for plants.

Autotrophs aren’t the only microbes that

enable life on Earth. Many heterotrophic bacte-

ria and archaeans are decomposers, consumers

that extract nutrients from the remains of dead

organisms and from waste products such as urine

and feces. Decomposers play a crucial role in

nutrient cycling: by breaking down dead organ-

isms or waste products, decomposers release

the chemical elements locked in the biological

material and return them to the environment.

Those released elements, such as potassium or

nitrogen or phosphorus, are used then by auto-

trophs and eventually by heterotrophs as well.

Healthy Balance

Since van Leeuwenhoek first looked through his

microscope, people tended to regard microbes

with suspicion and fear (Figure 15.11). We vilified