In which of the following organism , males are heterogametic and have chromosome number different than females ?

Options

A. Drosophila
B. Human
C. Birds
D. Bugs

Answer

To solve the question, "In which of the following organisms, males are heterogametic and have chromosome number different than females?" we will analyze each of the given options step by step.

### Step 1: Understand the terms "heterogametic" and "homogametic"
- **Heterogametic**: Refers to the sex that produces two different types of gametes. For example, males with XY chromosomes produce X and Y gametes.
- **Homogametic**: Refers to the sex that produces the same type of gametes. For example, females with XX chromosomes produce only X gametes.

### Step 2: Analyze the options

**Option 1: Drosophila (Fruit Fly)**
- In Drosophila, females are XX and males are XY.
- Both males and females have the same number of chromosomes (8 total: 3 pairs of autosomes and 1 pair of sex chromosomes).
- **Conclusion**: Males are heterogametic, but the chromosome number is the same. This option is incorrect.

**Option 2: Humans**
- In humans, females are XX and males are XY.
- Both males and females have the same number of chromosomes (46 total: 22 pairs of autosomes and 1 pair of sex chromosomes).
- **Conclusion**: Males are heterogametic, but the chromosome number is the same. This option is incorrect.

**Option 3: Birds**
- In birds, females are ZW and males are ZZ.
- Both males and females have the same number of chromosomes (80 total: 40 pairs).
- **Conclusion**: In this case, females are heterogametic. This option is incorrect.

**Option 4: Bugs**
- In bugs, females are XX and males are XO.
- Males produce two types of gametes (X and O), making them heterogametic.
- The chromosome number is different: females have 2 X chromosomes (XX) while males have 1 X and no second sex chromosome (XO).
- **Conclusion**: Males are heterogametic and have a different chromosome number than females. This option is correct.

### Final Answer:
The correct answer is **Bugs** (Option 4).

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