Fertilization that occurs outside the body, usually in water, is called which term?

• A. External fertilization
• B. Binary fission
• C. Commensalism
• D. Parasitism

Answer: (A)

External fertilization describes the fusion of sperm and egg that happens outside the bodies of the organisms, typically in water. In this mode, organisms release gametes into the environment, and fertilization occurs in the surrounding medium, which is common in many aquatic animals like fish and amphibians. This contrasts with internal fertilization, where fertilization occurs inside the female reproductive tract and is more common in terrestrial environments. The other terms don’t describe fertilization: binary fission is a form of asexual cell division, while commensalism and parasitism are types of symbiotic relationships, not reproductive processes.