Final answer:
Internal fertilization involves sperm fertilizing an egg within the female's body and offers protection for the embryo, while external fertilization occurs outside the body in the environment, leading to a higher number of offspring but increased vulnerability.
Step-by-step explanation:
In the context of sexual reproduction, fertilization can occur by either internal fertilization or external fertilization. Internal fertilization involves sperm being deposited inside the female's body, where it can fertilize an egg within the reproductive tract, as seen in humans, reptiles, birds, and some fish.
This method has several advantages, such as protecting the fertilized egg from dehydration, reducing predation on the embryos, and enhancing the likelihood of fertilization by a specific male, which can increase the survival rates of offspring. However, it generally results in fewer offspring being produced compared to external fertilization.
External fertilization, on the other hand, occurs when gametes are released into the environment, such as water, where fertilization takes place outside the body.
This method is common in many aquatic animals, such as fish and amphibians. The advantages of external fertilization include the potential for producing a large number of offspring, but this comes with higher susceptibility to environmental risks and a greater chance of predation on the eggs and embryos.