Rucete ✏ Campbell Biology In a Nutshell
Unit 5 THE EVOLUTIONARY HISTORY OF BIOLOGICAL DIVERSITY — Concept 31.2 Fungi Produce Spores Through Sexual or Asexual Life Cycles
Fungi reproduce by producing haploid spores through both sexual and asexual processes. These reproductive strategies allow fungi to disperse efficiently, colonize new environments, and generate genetic variation when conditions permit.
Sexual Reproduction in Fungi
- Most fungi have a haploid-dominant life cycle with a brief diploid stage during reproduction.
- Sexual reproduction involves:
- Plasmogamy: fusion of cytoplasm from two parent mycelia.
- Results in a heterokaryotic or dikaryotic stage (cells with two distinct nuclei).
- Karyogamy: fusion of haploid nuclei → forms diploid zygote.
- Meiosis: restores haploid state and produces genetically diverse spores.
- Plasmogamy: fusion of cytoplasm from two parent mycelia.
- Heterokaryotic/dikaryotic stages allow some benefits of diploidy, like buffering against harmful mutations.
- Sexual spores are often dispersed by wind or water; when conditions are favorable, they germinate into new mycelia.
Asexual Reproduction in Fungi
- Many fungi reproduce asexually by forming haploid spores via mitosis.
- These fungi are often called molds if they grow as visible mycelia.
- Molds reproduce rapidly and colonize food sources like bread or fruit.
- Some fungi, like yeasts, reproduce asexually via:
- Cell division or
- Budding (formation of small “bud cells” from parent cells).
- Deuteromycetes: a group of fungi with no known sexual stage.
- Classified into proper fungal phyla when sexual stages are discovered or through genomic analysis.
Real-Life Example: Spores on Melon
- Even without a visible source, a slice of melon left out will develop fuzzy mycelia in days.
- This demonstrates the effectiveness of spore dispersal—fungal spores are everywhere and can colonize suitable environments rapidly.
Scientific Study: Laccaria bicolor Genome
- Laccaria bicolor is a mycorrhizal fungus that forms mutualistic relationships with tree roots.
- Researchers sequenced its genome and compared it to nonmycorrhizal fungi.
- Findings:
- L. bicolor has significantly more genes for:
- Membrane transporters (for nutrient exchange)
- Small secreted proteins (SSPs)—likely key to symbiosis
- Gene expression differs in ectomycorrhizal mycelium vs. free-living mycelium, providing insight into mutualism mechanisms.
- L. bicolor has significantly more genes for:
In a Nutshell
Fungi reproduce by releasing spores that develop into new mycelia. Through sexual reproduction, they create genetically varied spores; through asexual methods like mold formation and budding, they reproduce rapidly. These strategies, combined with studies like Laccaria bicolor’s genome, reveal the remarkable adaptability and ecological partnerships of fungi.