Question

Describe the sequence of events that make up the alternation of generations in plants. Include an explanation of where mitosis and meiosis occur in the sequence.

Answer 1

Answer:

The description is provided in the explanation section below

Explanation:

ALTERNATION OF GENERATIONS is a unique phenomenon whereby certain organisms switch between a diploid state and a haploid state in their reproductive life cycle. It is a feature of plants (higher and lower).

A plant is a diploid organism (2n) i.e. contains two set of chromosomes. This diploid state of the plant is called the SPOROPHYTE. The diploid sporophyte (2n) of a plant undergoes meiotic division (reduction division) to produce haploid spores. These haploid spores germinates and grows via mitosis (duplication division) to form the haploid GAMETOPHYTE.

The haploid gametophyte (n), via structures called GAMENTAGIA, produces haploid gametes. The male gametophyte produces male gametes (sperm) while the female gametophyte produces female gamete (egg). These haploid gametes eventually fuse in a process called FERTILIZATION to produce a diploid ZYGOTE (2n) i.e. sperm (n) + egg (n) = zygote (2n). The ZYGOTE undergoes series of mitotic divisions (growth) to form the diploid SPOROPHYTE (2n) of the plant. The cycle restarts again in that order, hence it is called ALTERNATION OF GENERATIONS.

N.B: Mitosis maintains the number of chromosomes of the parent cell while meiosis reduces the chromosomal number of the parent cell by half.