Kaplan Nursing Entrance Practice Exam

External reproduction is primarily associated with which type of organisms?

1. Terrestrial mammals

2. Vertebrates in water

3. Insects on land

4. Amphibians in swamp areas

The correct answer is: Vertebrates in water

External reproduction primarily occurs in organisms that release gametes into their environment, allowing for fertilization to take place outside of the body. This method is predominantly seen in aquatic vertebrates, such as fish, which spawn in water where both eggs and sperm are released into the surrounding environment. In this context, vertebrates in water have evolved mechanisms that optimize external fertilization. For example, many species spawn in large groups to increase the likelihood of successful fertilization, which can be critical in environments where egg and sperm must meet in a vast aquatic space. While other organisms like terrestrial mammals and insects may reproduce via different methods, and although amphibians do have a mix of breeding strategies (some of which may involve external fertilization), the primary association of external reproduction is strongest with water-dwelling vertebrates. Thus, the correct answer accurately reflects the reproductive strategies of organisms that typically engage in this type of reproduction.