Fecundity is a measure of the number of offspring produced by an organism over time. It is also called the reproductive rate of an organism. Fecundity is measured by the number of offspring that are created successfully. In sexually reproducing organisms, two gametes must meet and the process of fertilization must occur. This embryo must then be developed, and birthed into the world, either directly from the zygote, or from a seed, an egg, or directly from the mother. Fecundity is a measure of the number ofviable offspring, or offspring that have the potential to continue on reproducing. Fertility, on the other hand, is simply the ability to sexually reproduce successfully.
A population exhibits more fecundity when each organisms produces more offspring successfully, and the population grows. Fertility is simply a description of whether or not individual animals are able to reproduce. An organism can produce many gametes ready for fertilization, but may never get the chance to reproduce. This organism would be fertile, but would show no fecundity. Fecundity can be measured in individual organisms, or in entire populations. The study of human demographics uses the measure of fecundity to help determine the rate of change a population is experiencing. Ecologists also use measures of fecundity to study reproductive rates in animal populations.