which of the following statements regarding fertilization and implantation are incorrect ?
I. During fertilization , a sperm first comes in contact with the corona radiata cells produced by the ovum.
II. Fertilization occurs only if sperm and ovum are simultaneously transported to the ampullary region.
III. Implantation occurs about 7 days after fertilization .
IV. The continuous division of morula leads to the formation of zygote.

Options

A. I and II
B. I , II and III
C. IV
D. II , III and IV

Answer

To determine which statements regarding fertilization and implantation are incorrect, we will analyze each statement one by one.

### Step 1: Analyze Statement I
**Statement I:** "During fertilization, a sperm first comes in contact with the corona radiata cells produced by the ovum."

- **Explanation:** This statement is correct. The sperm must first penetrate the corona radiata, which is the outer layer surrounding the ovum, before it can reach the zona pellucida and fertilize the egg.

### Step 2: Analyze Statement II
**Statement II:** "Fertilization occurs only if sperm and ovum are simultaneously transported to the ampullary region."

- **Explanation:** This statement is also correct. Fertilization typically occurs in the ampullary region of the fallopian tube, and for successful fertilization, both the sperm and ovum need to be present in this region at the same time.

### Step 3: Analyze Statement III
**Statement III:** "Implantation occurs about 7 days after fertilization."

- **Explanation:** This statement is correct as well. Implantation usually occurs between 6 to 12 days after fertilization, making this statement accurate.

### Step 4: Analyze Statement IV
**Statement IV:** "The continuous division of morula leads to the formation of zygote."

- **Explanation:** This statement is incorrect. The zygote is formed when the sperm fertilizes the ovum. The morula is formed after the zygote undergoes several rounds of mitotic division. Therefore, the continuous division of the zygote leads to the formation of the morula, not the other way around.

### Conclusion
After analyzing all statements, we find that **Statement IV is incorrect**. Therefore, the answer to the question is that the incorrect statement is Statement IV.

### Final Answer
The incorrect statement regarding fertilization and implantation is: **IV. The continuous division of morula leads to the formation of zygote.**

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