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.
Sperm or spermatozoa. The reproductive cell of the male, which contains genetic information and participates in the act of fertilization of an ovum. sperm. Male gamete or sex cell that contains the genetic information to be transmitted by the male, exhibits autokinesia, and is able to effect zygosis with an oocyte. sperm, n the cells contained in the male's semen that fertilize the female's egg during the process of conception.