Question

After karyogamy followed by meiosis, spores are produced exogenously in
A. Agaricus
B. Neurospora
C. Saccharomyces
D. Alternaria

Answer 1

Hint: In the five kingdom classification, kingdom fungi is included as a separate kingdom of organisms. These are cosmopolitan in nature showing a great diversity in morphology and habitat. The body of fungi is filamentous called mycelium. The cell wall of fungi is made up of chitin (fungal cellulose) which is a distinguishing character of fungi from the plants. As they lack chloroplasts, they are dependent on other organisms for their nutrition (heterotrophic nutrition).

Complete answer:
Reproduction in fungi is a very complex phenomenon. Fungi can reproduce through vegetative, sexual and asexual ways based on conditions favourable for them.
Sexual reproduction in fungi is a sequential process. It is completed in three steps namely- plasmogamy, karyogamy and meiosis, respectively.
Plasmogamy is the first stage of sexual reproduction in fungi. In this stage, two motile or non motile sex cells fuse with each other but their nuclei do not fuse, due to which a single cell has two nuclei. This is called the dikaryotic stage. Fusion of nuclei to form a diploid nucleus (Synkaryon) takes place in the karyogamy stage. Then, this diploid nucleus undergoes meiosis due to which haploid nuclei or haploid cells are formed.
In Agaricus, after the fusion of two vegetative cells (plasmogamy), a club shaped structure is formed on every cell (basidium). After that, both the nuclei come into this basidium and fuse with each other (karyogamy) and further, meiosis takes place as a result of which four haploid spores are formed on every basidium (basidiospores). These basidiospores are exogenous in nature and on germination produces new mycelium.
In Neurospora, the spores are endogenously formed in a sac like structure called ascus. Sexual reproduction is absent in Alternaria. In Saccharomyces (yeast), budding is the major form of reproduction.
Thus the correct answer is option A.

Note:
Vegetative reproduction in fungi occurs through fragmentation, budding and fission while asexual reproduction occurs through spore formation. Asexual spores are formed through mitotic division whereas sexual spores are formed through meiotic division. On the basis of structure of mycelium and type of sexual reproduction, fungi are classified as Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes. Ascus is a sac-like spore forming structure in ascomycetes and basidium is a spore forming structure in basidiomycetes.