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Biology for Advanced Level Secondary Schools

undergoing extracellular digestion. (c) They undergo sexual reproduction
However, some zygomycetes are involving two gametangia to produce
parasitic to plants, animals, and a resting spore known as zygospore.
insects.
(e) Their hyphae have three distinct parts, Structure of Rhizopus
namely sporangiophore, stolon, and The body of Rhizopus consists of branching
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rhizoids. mycelia composed of three types of
hyphae. These are stolons, rhizoids, and
Distinctive features of phylum sporangiophores (a stalk that arises from
Zygomycota the vegetative hypha). Sporangia (asexual
Members of the phylum Zygomycota have spore-forming structures) arise from stolons
the following features that differentiate
them from other phyla: opposite to rhizoids (Figure 3.19). Stolons
are the horizontal creeping hyphae that
(a) They have aseptate hyphae, which interconnect the upright growing hyphae.
lack cross walls between adjacent The sporangiospores are produced inside
cells. They are therefore coenocytic in the spherical structure called sporangium,
structure. which is supported by the columella.
(b) Their cytoplasm is continuous and
multinucleate.

Sporangium
Collumela Sporangiospores

Apophysis

Sporangiophore

Stolon

Mycellium

Rhizoids

Figure 3.19: Structure of a Rhizopus

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