Choose the incorrect statement from the following

Options

A. In birds and mammals, internal fertilization takes place
B. colostrum contains antibodies and nutrients
C. Polyspermy in mammals is prevented by the chemical changes in the sperm surface
D. In the human female implantation occurs almost seven days after fertilisation.

Answer

To solve the question "Choose the incorrect statement from the following," we will analyze each statement provided and determine which one is incorrect.

### Step-by-Step Solution:

1. **Analyze the First Statement:**
- The first statement claims that "birds and mammals undergo internal fertilization."
- Internal fertilization is defined as the fusion of male and female gametes occurring inside the female's body.
- In both birds and mammals, fertilization indeed occurs internally.
- **Conclusion:** This statement is **correct**.

2. **Analyze the Second Statement:**
- The second statement asserts that "colostrum contains antibodies and nutrients."
- Colostrum is the first milk produced by mammals after childbirth and is known to be rich in antibodies and essential nutrients for the newborn.
- **Conclusion:** This statement is **correct**.

3. **Analyze the Third Statement:**
- The third statement states that "polyspermy in mammals is prevented by the chemical changes in the sperm surface."
- Polyspermy refers to the fertilization of an egg by more than one sperm.
- In mammals, polyspermy is prevented primarily by the depolarization of the egg's plasma membrane after the first sperm binds to it, which prevents additional sperm from entering.
- The statement incorrectly attributes the prevention of polyspermy to chemical changes in the sperm surface rather than the egg's plasma membrane.
- **Conclusion:** This statement is **incorrect**.

4. **Analyze the Fourth Statement:**
- The fourth statement mentions that "in human females, implantation occurs almost 7 days after fertilization."
- Implantation is the process where the embryo attaches to the uterine wall and typically occurs about 6 to 12 days after fertilization.
- Thus, stating that it occurs almost 7 days after fertilization is accurate.
- **Conclusion:** This statement is **correct**.

### Final Conclusion:
The incorrect statement among the options provided is: "Polyspermy in mammals is prevented by the chemical changes in the sperm surface."