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 cell. Definition. noun, plural: sperm cells. A mature male gamete or reproductive cell; spermatozoon. Supplement. A single sperm cell consists of a round or cylindrical nucleated cell, a short neck, and a thin motile tail.Its structure is vital to its mobility and function (i.e. sexual reproduction).The compacted nucleus contains half of the genetic information. It fuses with an ovum (the female gamete) to form a zygote.In mammals, the sex is determined by the sperm cell. If it bears Y chromosome, the resulting offspring is a male.If X chromosome, the offspring is a female.t fuses with an ovum (the female gamete) to form a zygote. In mammals, the sex is determined by the sperm cell. If it bears Y chromosome, the resulting offspring is a male. If X chromosome, the offspring is a female.