However, human activities generate additional 'greenhouse gases'. Globally, atmospheric concentrations of two of the main greenhouse gases, carbon dioxide (CO2) and methane (CH4) have increased over the last 150 years. Agriculture has played a significant role in this-up to 35% of anthropogenic CH4 comes from animals and their wastes (Monteny et al. 2006).
sperm, sperm cell, spermatozoan, spermatozoon-the male reproductive cell; the male gamete; a sperm is mostly a nucleus surrounded by little other cellular material. egg cell, ovum-the female reproductive cell; the female gamete.
A spermatozoon or spermatozoan (pl. spermatozoa), from the ancient Greek ÏÏÎµÏÎ¼Î± (seed) and Î¶ÏÎ½ (alive), is more commonly known as a sperm or sperm cell. It is the haploid male gamete cell, meaning it is the reproductive cell containing a single set of chromosomes.