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 sperm cell is the male sex cell. All animals (and many other types of organisms) produce what are called sex cells. Sex cells, are the cells, that when combined, produce a completely new organism. For example, your mother and every other human female, carry egg cells (female sex cells) in their ovaries.perm, short for spermatozoon, is the male sex cell and, like the female egg cell, carries half of the DNA, or biological information, necessary to determine not only the type of organism, but also its characteristics. When the sperm cell and egg cell unite, an embryo is formed.