have a thallus many meters and penetrate its surroundings. In the hyphae of fungi
there is a portion called the vegetative hyphae. Vegetative hyphae are where nutri-
ents are obtained. The part of the hyphae responsible for reproduction is called
reproductive or aerial hyphae.
Fungi can reproduce both sexually and asexually. Reproduction occurs with
the formation of spores. Spores are always nonmotileand are a common means
of reproduction among fungi. Do not confuse bacterial endospores with fungal
spores; they are different. Bacterial endospores are formed so that the bacterial
cell can survive in harsh environments. Once there is a less threatening env-
ironment, the bacterium leaves the endospore state and becomes active. The
endospore germinates into a single bacterial cell. Asexual reproduction occurs
whenasexual sporesare formed by the hyphae of one organism. When these
spores germinate, they are identical to the parent. Sexual reproductionhappens
when the nuclei of sexual sporesfrom two opposite mating strains of the same
fungus species fuse. Fungi that grow from sexual spores have genetic character-
istics of both parents.
YEASTS
Yeasts are fungi that are unicellular and reproduce using a process called fission,
although some can form filaments. Fissionoccurs when a cell divides evenly to
form two new cells. When the cell divides by budding, it divides unevenly.
Yeasts are nonfilamentous and have a spherical or oval shape. The white pow-
CHAPTER 11 The Eukar yotes^169
Fig. 11-1. The body of a fungus contains
long filaments called hyphae.