Eukaryotes have many organelles. Prokaryotes have fewer organelles. Most viruses have only two organelles. Cell biology studies the organelles of cells and viruses. How radiation dose and exposure determine survival from atomic explosions and accidents.
Some organism have two lives, a diploid and a haploid phase of their life cycle.
Sperm and eggs are produced by a process of meiosis. There are two cell divisions involved, reduction division and equation division. There is only one egg from each immature reproductive cell. The autosomes are numbered 1 to 22. At fertilization this leads to abnormal embryos most of which abort.