Biology · Biological Classification · NEET
Plasmogamy means fusion of the protoplasm (cytoplasm) of two gametes or cells. Their two nuclei come close but do NOT fuse yet. Karyogamy is the next step, where those two nuclei fuse into one diploid (2n) nucleus. Simple trick: 'plasm' = plasma/cytoplasm fuses first; 'karyo' = karyon = nucleus fuses second.
The order is fixed: (1) Plasmogamy, (2) Karyogamy, (3) Meiosis. Cytoplasm fuses, then nuclei fuse to make 2n, then meiosis reduces it back to haploid (n) spores. NEET loves this exact sequence in match-the-column questions, so never swap the order.
Karyogamy makes a DIPLOID (2n) nucleus, because it fuses two haploid (n) nuclei into one. This is the only diploid stage in most fungi. Meiosis then follows and brings it back to haploid (n) spores. So: karyogamy = builds up to 2n, meiosis = cuts down to n.
Meiosis must reduce the diploid nucleus (formed by karyogamy) back to haploid. So a diploid nucleus must exist first. That is why the order is plasmogamy, then karyogamy (makes 2n), then meiosis (makes n spores). Meiosis is called reduction division because it halves the chromosome number.
In some fungi (ascomycetes and basidiomycetes), after plasmogamy the two nuclei do NOT fuse right away. The cell holds two separate nuclei (n+n) — this is the dikaryon or dikaryophase. Karyogamy is delayed until later, then meiosis follows. In lower fungi (like phycomycetes), karyogamy happens immediately, so there is no dikaryon.
The spores made after meiosis are HAPLOID (n). Meiosis takes the diploid (2n) nucleus and halves it. Examples of these sexual spores are oospores, ascospores and basidiospores. These form inside distinct structures called fruiting bodies.
Match List-I with List-II: List-I A. Fusion of protoplasms between gametes B. Fusion of two nuclei C. Generation of haploid spores List-II I. Meiosis II. Plasmogamy III. Karyogamy Choose the correct answer:
After karyogamy followed by meiosis, spores are produced exogenously in:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Plasmogamy (fusion of protoplasm), karyogamy (fusion of two nuclei to form a diploid nucleus), and meiosis (reduction division that forms haploid spores). This exact order is a common NEET question.
Plasmogamy is when the cytoplasm (protoplasm) of two fungal cells or gametes fuses together. The two nuclei come inside one cell but stay separate for now.
Karyogamy is the fusion of the two nuclei to make a single diploid (2n) nucleus. It comes right after plasmogamy in fungi that fuse nuclei immediately, or after a delay in ascomycetes and basidiomycetes.
Karyogamy makes a diploid (2n) nucleus. Meiosis (reduction division) halves it back to haploid (n), producing haploid sexual spores like oospores, ascospores or basidiospores. This keeps the chromosome number stable across generations.
Ascospores form INSIDE a sac-like ascus (endogenous). Basidiospores form OUTSIDE, on the surface of the basidium (exogenous). NEET 2018 tested that exogenous spores after karyogamy and meiosis point to Agaricus (a basidiomycete).
