Which one of the following organisms produces the female gamete by mitosis of haploid cells?
Show Hint
In all plants (mosses, ferns, angiosperms), gametes are always produced by mitosis because they arise from a haploid gametophyte.
In contrast, animals always produce gametes by meiosis from diploid cells.
Step 1 : Understanding the Question:
The question asks to identify which of the given organisms produces its female gamete (egg cell) through the process of mitosis within haploid cells, rather than through meiosis of diploid germ cells. Step 2 : Key Formulas and Approach:
The approach involves distinguishing between the life cycles of land plants (which exhibit alternation of generations) and animals (which have a diplontic life cycle). Step 3 : Detailed Explanation:
• Alternation of Generations (Plants): In land plants like the garden pea (Pisum sativum), the diploid sporophyte produces haploid spores via meiosis.
• Gametophyte Development: The haploid megaspore undergoes several rounds of mitosis to form the multicellular haploid female gametophyte (known as the embryo sac).
• Gamete Production: Within this haploid embryo sac, the egg cell (female gamete) is produced directly by mitotic division of a haploid precursor cell. This matches the condition in the question.
• Animal Life Cycles: In animals like the honey bee, fruit fly, and chicken, there is no multicellular haploid stage.
• These animals are diploid, and their female gametes (eggs) are produced directly via meiosis of diploid germline cells in the ovaries. Step 4 : Final Answer:
Thus, only the garden pea produces its female gametes by the mitosis of haploid cells.
This corresponds to Option (A).
