This amongst the following statements is incorrect. Human spermatozoa usually

The correct option (the incorrect statement about human spermatozoa) is:
"at a concentration of 1 million/ml of ejaculate will fertilize the ovum"

To understand why this statement is incorrect, let us evaluate the physiology of human semen and fertilization step-by-step:

1. Sperm Concentration and Infertility:
A normal human sperm count ranges from 15 million to over 200 million spermatozoa per milliliter (ml) of semen. According to the World Health Organization (WHO) guidelines, a sperm concentration of less than 15 million/ml is considered abnormally low (a condition known as olgozoospermia) and is highly associated with male infertility.

A concentration as low as 1 million/ml is extremely severe oligozoospermia. At this concentration, the probability of natural fertilization of the ovum is virtually zero because the vast majority of sperm are destroyed by the acidic environment of the female reproductive tract before reaching the fallopian tubes. Therefore, the statement that sperm at a concentration of 1 million/ml will fertilize the ovum is incorrect.

2. Why the other statements are correct:

• "moves with the help of their tails": Sperm cells are flagellated. The flagellum (tail) uses ATP to whip back and forth, providing motility to swim through the female reproductive tract.
• "contains enzyme in their head which aids in penetration of the ovum": The head of the sperm is capped by the acrosome, a lysosome-like organelle containing hydrolytic enzymes (such as hyaluronidase and acrosin). These enzymes digest the outer protective layers of the egg (corona radiata and zona pellucida) to allow fertilization.
• "are released in large numbers after a few days of abstinence": Semen volume and sperm count accumulate in the epididymis and vas deferens when ejaculation does not occur. Consequently, a short period of abstinence (usually 2 to 7 days) results in a significantly higher total sperm count upon ejaculation.