If they have adequate oxygen, they will completely oxidize their carbon sources, usually sugars, to carbon dioxide and water. However, under anaerobic conditions, deprived of oxygen, yeast can convert sugars only to carbon dioxide and ethanol, recovering less of the energy. In either case, growth will be limited by some essential nutrient or the accumulation of the toxin. Yeast grow equally well in liquid media or on a nutrient surface such as an agar plate or an exposed surface of some kind of food. On a nutrient surface in a ventilated container, they grow aerobically with each cell forming a visible colony of up to 100 million cells within 2 or 3 days.
Meiosis yields four haploid nuclei.
During meiosis, paired homologous chromosomes in the diploid nucleus interchange parts and are distributed into the haploid nuclei yielding new combinations of genetic traits. The germ-cell line produces the reproductive cells that form the gametes . The gametes are the cells which carry the genetic information to the next generation while the somatic cells form the rest of the organism and play no direct role in heredity. This leads to the formation of a zygote in which two parental haploid nuclei fuse to form a diploid nucleus. In higher organisms, the gametes are differentiated germ line cells.