The production of gametes by the parents, formation of zygotes, the F₁ and F₂ plants, can be understood from a diagram called :

The correct answer is Punnett square.

Step-by-Step Explanation:

1. In genetics, we study how traits are passed down from parents to offspring. The parents produce haploid reproductive cells called gametes (such as pollen/sperm and egg cells) through meiosis. Each gamete carries one allele for each gene.
2. When fertilization occurs, two gametes fuse to form a diploid cell called a zygote, which develops into the offspring (such as the first filial generation, or $F_1$, and the second filial generation, or $F_2$ plants).
3. To visualize and calculate the probability of all possible genotypes and phenotypes resulting from these genetic crosses, British geneticist Reginald C. Punnett developed a simple graphical representation.
4. This diagram is a grid layout where the gametes of one parent are written along the top, and the gametes of the other parent are written along the left side. The intersections of the grid columns and rows represent the potential zygotic combinations (genotypes) of the offspring.
5. Therefore, this diagram is called a Punnett square.