<em>The life cycles of sexually producing organisms generally involve alternation between the haploid and diploid generations.</em>
<u>Sexual reproduction involves the fusion of gametes - fertilization. The gametes are haploid (n) and are usually formed by the reductional division (meiosis) of diploid (2n) sex cells. </u>
Haploid gametes represent the haploid stage of the life cycles of sexually reproducing organisms. During fertilization, the male and female gametes fuse together to form a diploid zygote. The zygote then continues to divide equationally (mitosis) and differentiates to give rise to a baby and eventually to either male or female adult organism.
During cellular respiration, a glucose molecule is gradually broken down into carbon dioxide and water. Along the way, ATP is produced directly in the reactions that transform glucose. However, more ATP is later produced in a process called oxidative phosphorylation.
