A zygospore is a diploid reproductive stage in the life cycle of many fungi and protist
Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...

s. Zygospores are created by the nuclear fusion of haploid cells. In fungi, zygospores are termed chlamydospore
A Chlamydospore is the thick-walled big resting spore of several kinds of fungi. It is the life-stage which survives in unfavourable conditions, such as dry or hot seasons....

s and are formed after the fusion of hyphae of different mating types. In many eukaryotic algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, including many species of the Chlorophyta
Chlorophyta is a division of green algae, informally called chlorophytes. The name is used in two very different senses so that care is needed to determine the use by a particular author...

, zygospores are formed by the fusion of unicellular gametes of different mating types.

A zygospore remains dormant while it waits for environmental cues, such as light, moisture, heat, or chemicals secreted by plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s. When the environment is favorable, the zygospore germinates, meiosis occurs, and haploid vegetative cells are released.

In fungi, a sporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...

 is produced at the end of a sporangiophore that sheds spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s. A fungus that forms zygospores is called a zygomycete, indicating that the class
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

is characterized by this evolutionary development.

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