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 uniflagellar sperm cell that is motile is referred to as a spermatozoon, whereas a non-motile sperm cell is referred to as a spermatium.Sperm cells cannot divide and have a limited life span, but after fusion with egg cells during fertilization, a new organism begins developing, starting as a totipotent zygote. uniflagellar sperm cell that is motile is referred to as a spermatozoon, whereas a non-motile sperm cell is referred to as a spermatium.