Question

In which animal do haploid cells divide mitotically to produce gametes ?

• A. Male frogs
• B. Male honeybees
• C. Male grasshoppers
• D. Male earthworms

Hint:

Logic Tip: The phenomenon where males develop from unfertilized eggs is called arrhenotoky. Remember: Drones (male bees) have no father and cannot have sons, but they have a grandfather and can have grandsons!

Answer 1

The Correct Option is B

Step 1 : Understanding the Question:
While most diploid animals produce haploid gametes through meiosis (reductional division), this question asks for an organism where gametes are produced via mitosis from cells that are already haploid. This is only possible in organisms that are haploid as adults.
Step 2 : Key Formulas and Approach:
The approach involves analyzing the ploidy and developmental biology of each animal:
1. Male Frogs: Diploid vertebrates that use meiosis.
2. Male Honeybees: Haploid insects developed from unfertilized eggs.
3. Male Grasshoppers: Diploid insects that use meiosis.
4. Male Earthworms: Diploid hermaphroditic organisms that use meiosis.
Step 3 : Detailed Explanation:

Male Frogs (A): Frogs are standard diploid ($2n$) vertebrates. Their germ cells must undergo meiosis to reduce the chromosome number by half to produce haploid ($n$) sperm. This is typical of most animals.

Male Grasshoppers (C) and Earthworms (D): Both are diploid organisms. Grasshoppers are XO but still diploid in nature, and earthworms are $2n$. They both rely on meiosis to produce their gametes.

Male Honeybees (B): Honeybees utilize a unique haplodiploid sex-determination system. While females (queens and workers) are diploid ($2n=32$) and hatch from fertilized eggs, the males (drones) develop through arrhenotoky—a form of parthenogenesis where unfertilized eggs develop into adults. Because they come from unfertilized eggs, drones are haploid ($n=16$) for their entire lives.

Gametogenesis: Since a drone's body cells are already haploid, his germ cells cannot undergo meiosis (which would attempt to halve 16 chromosomes into 8, resulting in non-functional gametes). To produce haploid sperm cells with a full set of 16 chromosomes, the drone must use mitosis.

Step 4 : Final Answer:
Male honeybees are the only organisms listed that are haploid and thus must produce their gametes via mitosis. Therefore, the correct option is (B).