The level of which of the following ions increases after fusion of the egg and sperm plasma membranes?Multiple choice question.K+Cl-Na+Ca2+

The ion that primarily increases in concentration after the fusion of the egg and sperm plasma membranes is Ca²⁺ (Calcium ion).

Explanation:

1. Fusion Process: The fusion of the egg and sperm plasma membranes initiates several cellular responses, one of which is an increase in intracellular calcium levels.
2. Role of Ca²⁺: The rise in Ca²⁺ concentration is crucial for various physiological processes, including the activation of metabolic pathways, triggering the completion of meiosis in the egg, and initiating embryonic development.
3. Other Ions: While K⁺ (Potassium), Cl⁻ (Chloride), and Na⁺ (Sodium) are important ions in cellular functions, they do not show the same dramatic increase in concentration upon fertilization as Ca²⁺ does.

In summary, the correct answer to the multiple-choice question is Ca²⁺.