Reproductive (haploid) cells known as gametes have half as many (23) pairs of chromosomes as normal (diploid) cells. When the male gamete (sperm) combines with the female gamete (ovum) through meiosis to form a zygote, each gamete supplies half the chromosomes needed to form the normal diploid cells.

Temperatures again increase with altitude in the thermosphere which is the hottest (4,530 °F / 2,500 °C) atmospheric layer due to direct exposure to the Sun's radiation. However, the gas in this layer is highly diluted so even though the atoms of gas may be very high in temperature, there are too few of them to effectively transfer much heat.

The Fahrenheit scale is used for measuring temperature in the British system. The metric system uses the Celsius scale.

The rows of the Periodic Table are called periods and contain elements that have the same number of electron shells ordered from lower to higher atomic number. 

If no oxygen is present, cellular respiration is anaerobic and will result in fermentation where either lactic acid or alcohol is used instead of oxygen.