Question

Meiosis occurs in the zygote of
A. Funaria
B. Chlamydomonas
C. Dryopteris
D. Puccinia

Answer 1

Meiosis is the division of chromosome number into half. It ensures the production of the haploid phase in the life cycle of sexually reproducing organisms. It involves the pairing of homologous chromosomes and recombination between them.

Complete answer:
The production of offspring by sexual reproduction includes the fusion of two gametes, each with a complete haploid set of chromosomes. Gametes are formed from specialized diploid cells. This specialized kind of cell division that reduces the chromosome number by half results in the production of haploid daughter cells. This kind of division is called meiosis.

Let us, first study division, in each case given in the options:
1. FUNARIA- It is a species of moss that is most common. It is monoecious because the male and the female reproductive structures develop on separate shoots of the same plants. The spore mother cells are the last structure of the sporophyte generation. They get differentiated by the process of meiosis into spores, which are the first structure of the next gametophyte generation.
2. Chlamydomonas - Reproduction in them is through isogamous, anisogamous or by oogamous. It is an example of algae with a haplontic life cycle. They produce gametes through mitosis. After the fertilisation, zygotes are formed which are diploid. Zygospore is the only diploid cell in the entire cycle which later undergoes meiosis to form haploid offspring.
3. Dryopteris- They are common wood ferns that are found in Asia, America and many other countries. Hybridisation and polyploidy are well-known phenomena through which new species are formed. There is no formation of the zygote in them.
4. Puccinia- It is a genus of fungi that are obligate plant pathogens and are known as rusts. Mitosis in the nuclei of the hyphae takes place in them to increase their number. The non - lining nucleus was surrounded by a double membrane which was interrupted by scattered pores. As mitosis progresses into the intranuclear system of microfibrils, it results in daughter SPBs.

So, the correct answer is option B, Chlamydomonas.

Note: Meiosis is the mechanism by which conservation of specific chromosome number of each species is achieved across generations in sexually reproducing organisms, even though the process results in a reduction of chromosome number by half. It also increases the genetic variability in the population of organisms from one generation to the next.