Assertion (A): Meiosis is also known as reduction division. Reason \((\mathbf{R}):\) Meiosis involves formation of daughter cells with half the number of chromosomes than that of parent cell. (a) Both \(\mathrm{A}\) and \(\mathrm{R}\) are true and \(\mathrm{R}\) is the correct explanation for \(\mathrm{A}\). (b) Both \(\mathrm{A}\) and \(\mathrm{R}\) are true and \(\mathrm{R}\) is the not the correct explanation for \(\mathrm{A}\). (c) \(\mathrm{A}\) is true and \(\mathrm{R}\) is false. (d) \(\mathrm{A}\) is false and \(\mathrm{R}\) is true.

Meiosis is a special type of cell division that reduces the genetic material by half, resulting in the formation of daughter cells. These cells are crucial for sexual reproduction because they develop into gametes—sperm in males and eggs in females. Unlike mitosis, where one division creates two identical cells, meiosis consists of two divisions: Meiosis I and Meiosis II.

During Meiosis I, homologous chromosomes—pairs of the same chromosome from each parent—separate into different cells. Meiosis II, similar to mitosis, then separates the chromatids, ultimately resulting in four genetically unique daughter cells, each with a single set of chromosomes. This variability is essential for genetic diversity, which is a cornerstone of evolution and species survival.

Also, during meiosis, processes like crossing over and random assortment enhance genetic diversity. Crossing over is the exchange of genetic material between homologous chromosomes, while random assortment refers to the random distribution of chromosomes into daughter cells. These processes ensure that the resulting daughter cells are genetically distinct from one another and from the parent cell.

Understanding the concept of chromosome number is crucial when studying meiosis. Every species has a characteristic number of chromosomes that are found in the nucleus of each cell. In humans, for example, each somatic (body) cell typically contains 46 chromosomes, which is the diploid number (2n).

During the process of meiosis, this number is reduced by half to form gametes with the haploid number (n), which in humans is 23. This reduction ensures that when fertilization occurs, the resulting zygote will have the correct diploid number of chromosomes: one set from the mother and one set from the father.

This reduction is achieved first by separating homologous chromosome pairs in Meiosis I and then by segregating sister chromatids in Meiosis II. The fundamental importance of maintaining a stable chromosome number across generations cannot be overstated, as it is essential for normal development and the survival of species.

In the context of cell division and heredity, cells are characterized as either haploid or diploid depending on the number of chromosome sets they possess. A diploid cell, designated as '2n', contains two complete sets of chromosomes—one set inherited from each parent. This is the condition found in the somatic cells of most organisms, including humans.

A haploid cell, symbolized by 'n', contains just one set of chromosomes. Gametes are haploid so that upon fertilization, when two gametes merge, they restore the diploid state in the new organism. This alternation of haploid and diploid stages is vital for sexual reproduction and ensures genetic variation.

The shift from diploid to haploid is not just a reduction in chromosome quantity; it also represents a critical shuffling of genetic information which provides the raw material for evolutionary processes. The balancing act between haploid and diploid phases, and the transitions between them, are central themes in biology that underscore the complexity and elegance of life's continuity.