Biology Now, 2e

The Dirt on Black-Market Plants ■ 295

white truffles cannot be cultivated in greenhouses

as other fungi can.

There’s danger in the forests too. Truffle hunt-

ers use dogs and pigs to sniff out wild truffles

(Fig ure 16.10), and some have reported compet-

itors planting spiked traps or poisoned meat-

balls in forests to eliminate trained dogs. Other

hounds have been stolen from their owners,

never to be seen again.

That’s a lot of drama for some fungi. Most

fungi are multicellular, but there are some single-

celled species collectively known as yeasts. Many

of us are familiar with yeasts thanks to two

important products they produce: alcohol and

carbon dioxide, crucial to the rising of bread, the

brewing of beer, and the fermenting of wine.

Fungi’s key evolutionary innovation is their

body form, which is well suited for absorptive

heterotrophy (Figure 16.11). They are made up

of a network of fine, colorless, branching, hair-

like threads called hyphae (singular “hypha”),

which absorb nutrients from the environment.

The entire bundle of hyphae, composing the

main body of the fungus, is called the mycelium

(plural “mycelia”).

Because of this unique body form, many fungi

are decomposers and consume nonliving organic

material. As they eat, these fungi release back

into the environment inorganic chemicals that

had previously been trapped in the bodies of

dead organisms. Once these chemicals are back

in the environment, plants and algae scoop them

up and use them to manufacture food. Fungi

interact with plants in other important ways too:

the vast majority of wild plants have mutualistic

fungi in their root systems that help the plants

The mycelium is the

bundle of hyphae that

make up an individual

fungus.

The fruiting body

of the fungus is what

we informally call

a “mushroom.”

Spores are the

reproductive

structures of

the fungus.

A hypha is a

single fungal

thread.

Figure 16.11

A fungus lives both belowground

and aboveground

The main body of a fungus is unseen, belowground. To reproduce,

the fungus generates a fruiting body that is usually aboveground and

releases spores. Spores travel by wind and develop into new fungi.

Q1: Why is it important that the fruiting body is aboveground?

Q2: What part of a fungus is the mushroom that you can buy in the

grocery store?

Q3: Write a sentence in your own words that uses the terms

“mycelium,” “fruiting body,” and “spore” correctly.

Figure 16.10

A truffle hunter and his dog search for a

fungus beloved by gourmets

While farmers continue attempts to grow truffles

commercially, their success has been limited. For

now, we must rely on truffle hunters and their

dogs (or pigs, which can also be trained to sniff

out truffles) for this fungal delicacy.