An adult organism produces gametes that quickly go through fertilization and form diploid zygotes. The zygotes mature into adults, which live for many years. Eventually the adults produce gametes and the cycle repeats. What type of life cycle does this organism have?

Diploid life cycle

Explanation:

The life cycle is the series of events that a sexually reproducing organism go through in a cycle. Life cycle may be diploid or haploid.

The major portion of adult life is spent as diploid in diploid life cycle of orgamism. For reproduction they produce haploid spores and those spores quickly fertilize to form diploid zygote. That zygote enters the cell cycle and after several mitosis and cell divisions the mature diploid organism is formed and the cycle continues.

Example; Plasmodial slime mold follows the diploid life cycle.