Describe the life cycle of us humans. Are the tissues and organs in our bodies made up of diploid cells or haploid ones? Our reproductive organs make sperm cells in males and egg cells in females. Is this done by mitosis or meiosis? When our bodies make gametes, does every cell in our body become a sperm cell or an egg cell, or do just some of the cells in our reproductive organs do this? Can our haploid sperm and egg cells undergo mitosis and grow into new animals that look like us but are haploid instead? (Haploid eggs do grow in bees. They develop into males.) After a fertilized egg (a zygote) is formed, is it diploid or haploid? Can it immediately undergo meiosis to make four new sperm cells or egg cells, or can it only grow by mitosis into another person?