Can someone please explain to me what’s happening in this picture figure 18.17 - The sequence of depolarization and repolarization of the heart related to the ECG waves.

that is wrong, its not thymus.

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.