Which of the following statements is not correct regarding sexuality in organisms ?

Options

A. When both male and female flowers are present on the same plant, the condition is said to be monoecious and is present in cucurbits and coconuts.
B. When both male and female flowers are present on the separate plants, the condition is said to be dioecious and is present in papaya and date palms.
C. In earthworm, both male and female sex organs are present in the same individual and therfore, self-fetillsation occurs in them.
D. Cockroach is a unisexual animal and exhibit sexual dimorphism.

Explanation

To determine which statement is not correct regarding sexuality in organisms, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1**: "When both male and female flowers are present on the same plant, the condition is said to be monoecious and is present in coconuts."
- **Analysis**: This statement is correct. Monoecious plants have both male and female reproductive structures on the same individual. Coconuts are indeed an example of monoecious plants.

2. **Statement 2**: "When both male and female flowers are present on separate plants, the condition is said to be dioecious and is present in papaya and date palms."
- **Analysis**: This statement is also correct. Dioecious plants have male and female reproductive structures on separate individuals. Papaya and date palms are examples of dioecious plants.

3. **Statement 3**: "In earthworm, both male and female sex organs are present in the same individual; therefore, self-fertilization occurs in them."
- **Analysis**: This statement is incorrect. While it is true that earthworms are hermaphrodites and possess both male and female sex organs, they do not typically undergo self-fertilization. Instead, they usually engage in cross-fertilization because their reproductive organs mature at different times.

4. **Statement 4**: "Cockroach is a unisexual animal."
- **Analysis**: This statement is correct. Cockroaches are indeed unisexual, meaning that individual cockroaches are either male or female, not both.

### Conclusion:
The statement that is not correct regarding sexuality in organisms is **Statement 3**.

### Final Answer:
**Option C** is the incorrect statement.

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