What are the advantages (and disadvantages) of external and internal fertilization? Is one mode better than the other?
For external fertilization to occur, gametes must be released into the environment. There, sperm cells and egg cells come into contact. Although this process requires a low investment of energy, fertilization becomes a matter of chance. Because of this, animals using this mechanism often produce more gametes to increase the likelihood of success. This type of fertilization also requires the animal to be tied to water, because it is only in liquid that gametes can move freely through the environment.
Internal fertilization is a much better mechanism. Animals can produce fewer gametes because there is a much higher chance of fertilization with copulation. These organisms are also not tied to aquatic environments. Most importantly, however, is the ability for mates to be chosen through this process. With internal fertilization, animals can be more selective of their mate, which prompts natural selection to occur. Over time, the fitness of the population increases because of this.