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.
The human sperm cell is haploid, so that its 23 chromosomes can join the 23 chromosomes of the female egg to form a diploid cell.In mammals, sperm develops in the testicles and is released from the penis. uniflagellar sperm cell that is motile is referred to as a spermatozoon, whereas a non-motile sperm cell is referred to as a spermatium.