12Reproduction and Meiosis
The earth is believed to house over 10 million species of organisms that have prospered by reproducing individuals of the same species. Thus, one of the most distinct characteristics of organisms is their creation of progeny while replicating their own genomes; this mechanism is called reproduction. To perform reproduction, organisms, including humans, have created and utilized sexes. However, many organisms do not use sexes for reproduction. As an example, unicellular organisms essentially multiply through somatic cell division, which replicates the same cells. Among multicellular organisms, some animals multiply by budding, and some plants multiply through regeneration from vegetative organs (e.g., potatoes). What, then, is the purpose of reproduction using sexes? The key to answering this question lies in meiosis and fertilization. This chapter discusses the roles that sexes play by focusing on these two processes.